Dopant-assisted direct analysis in real time mass spectrometry

FIELD OF THE INVENTION

The present invention relates to methods and devices for Direct Analysis in Real Time analysis with carrier gases in the presence of dopants.

BACKGROUND OF THE INVENTION

Direct Analysis in Real Time (DART) mass spectrometry is an ambient ionization method that is based on the interactions of excited-state atoms or molecules with the analyte and atmospheric gases. With helium as the DART gas, the dominant positive-ion formation mechanism is commonly attributed to Penning ionization of atmospheric water by the very long lived (metastable) He* 2³S₁state or 2³S₀state. The He 2³S₁state has an internal energy of 20.6 eV, while the He 2³S₀state has an internal energy of 19.8 eV, which both exceed the 12.62 eV ionization energy of water. Following the initial Penning ionization step, proton transfer reactions occur between protonated water clusters and analytes with proton affinities greater than that of water (691 kJ mol-1). Other reaction mechanisms are possible, but the ionization energy and proton affinity of water are the dominant parameters for undertaking analysis with helium DART.

The internal energies of the metastable states for other noble gases neon, argon, krypton and xenon are 16.61 eV, 11.55*, 9.915, and 8.315 eV, respectively, (*for the ³P₂state, (11.72 eV for the ³P₀state). Neon DART results in identical chemistry to helium DART because its internal energy is greater than the ionization energy of water. Although it is not a noble gas, nitrogen has a number of long-lived vibronic excited states. The mechanisms involved in nitrogen DART are not well understood. The maximum energy available for Penning ionization by N₂* is given as 11.5 eV, but protonated water and ammonia and other species can be observed in the background mass spectrum with nitrogen DART gas. Further, NO⁺ can be observed in nitrogen DART and is known to be a very reactive chemical ionization reagent ion.

SUMMARY OF THE INVENTION

In various embodiments of the present invention, a dopant is used together with argon DART in order to generate ions of analytes with different characteristics to the ions of the same analytes generated from conventional DART. In an embodiment of the invention, the combination of the conventional DART and argon DART spectra can be used to identify differences between analytes. In an alternative embodiment of the invention, the combination of the DART spectrum and the fragmentation spectrum of species generated with argon DART can be used to identify differences between analytes. In another embodiment of the invention, the combination of the conventional DART and argon DART spectra can be used to obtain structural information about an analyte. In another alternative embodiment of the invention, the combination of the DART spectrum and the fragmentation spectrum of species generated with argon DART can be used to obtain structural information about an analyte.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention is described with respect to specific embodiments thereof. Additional aspects can be appreciated from the Figures in which:

FIG. 1A shows a background positive-ion argon DART mass spectrum with no dopant and the y-axis scale magnified by 833;

FIG. 1B shows a background positive-ion argon DART mass spectrum with an acetone dopant, according to an embodiment of the invention;

FIG. 1C shows a background positive-ion argon DART mass spectrum with a toluene dopant, according to an embodiment of the invention;

FIG. 1D shows a background positive-ion argon DART mass spectrum with a toluene and 0.5% anisole dopant, according to an embodiment of the invention;

FIG. 1E shows a background positive-ion argon DART mass spectrum with a chlorobenzene dopant, according to an embodiment of the invention;

FIG. 2A shows a dopant-assisted argon DART mass spectrum for the PAH mixture at a concentration of 10 parts per million (ppm), according to an embodiment of the invention;

FIG. 2B shows a dopant-assisted argon DART mass spectrum for the PAH mixture at a concentration of 500 parts per billion (ppb), according to an embodiment of the invention;

FIG. 2C shows a dopant-assisted argon DART mass spectrum for the PAH mixture at a concentration of 5 ppb, where the inset shows the fluorene molecular ion resolved from background interferences, according to an embodiment of the invention;

FIG. 3A shows a mass spectrum of diesel fuel analyzed by dopant-assisted argon DART with the toluene/anisole dopant, according to an embodiment of the invention;

FIG. 3B shows a mass spectrum of diesel fuel analyzed by helium DART, according to an embodiment of the invention;

FIG. 4A shows a mass spectrum of the negative-ion background for dopant-assisted negative-ion argon DART, according to an embodiment of the invention;

FIG. 4B shows a mass spectrum of dopant-assisted argon DART of TNT with toluene/0.5% anisole dopant, according to an embodiment of the invention;

FIG. 4C shows a mass spectrum of the helium DART of TNT;

FIG. 5A shows a mass spectrum of dopant-assisted argon DART of THC with an orifice-1 voltage of 20V, according to an embodiment of the invention;

FIG. 5B shows a mass spectrum of dopant-assisted argon DART of CBD with an orifice-1 voltage of 20V, according to an embodiment of the invention;

FIG. 5C shows a mass spectrum of dopant-assisted argon DART of THC with an orifice-1 voltage of 60V, according to an embodiment of the invention;

FIG. 5D shows a mass spectrum of dopant-assisted argon DART of CBD with an orifice-1 voltage of 60V, according to an embodiment of the invention;

FIG. 5E shows a mass spectrum of dopant-assisted argon DART of THC with an orifice-1 voltage of 90V, according to an embodiment of the invention;

FIG. 5F shows a mass spectrum of dopant-assisted argon DART of CBD with an orifice-1 voltage of 90V, according to an embodiment of the invention;

FIG. 6 shows a schematic of the position of the DART gun relative to orifice-1 in the DART source, according to various embodiments of the invention;

FIG. 7A shows a schematic of a DART source for operating as conventional DART source or a dopant DART source, according to various embodiments of the invention;

FIG. 7B shows a schematic of a dual source for operating simultaneously as a conventional DART source and a dopant DART source, according to various embodiments of the invention;

FIG. 7C shows a schematic of a DART source for operating as a conventional DART source or a dopant DART source with a dual dopant reservoir, according to various embodiments of the invention;

FIG. 7D shows a schematic of a dual DART source for operating simultaneously as a conventional DART source and a dopant DART source with a dual dopant reservoir, according to various embodiments of the invention;

FIG. 7E shows a schematic of a dual DART source for operating simultaneously as a conventional DART source and a dopant DART source with multiple dopant reservoirs, according to various embodiments of the invention;

FIG. 7F shows a schematic of a DART source for operating as conventional DART source or a dopant DART source with a dual dopant reservoir, according to various embodiments of the invention; and

FIG. 7G shows a schematic of a dual DART source for operating simultaneously as a conventional DART source and a dopant DART source with multiple dopant reservoirs, according to various embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION
Definitions

The transitional term ‘comprising’ is synonymous with ‘including’, ‘containing’, or ‘characterized by’, is inclusive or open-ended and does not exclude additional, unrecited elements or method steps.

The transitional phrase ‘consisting of’ excludes any element, step, or ingredient not specified in the claim, but does not exclude additional components or steps that are unrelated to the invention such as impurities ordinarily associated with a composition.

The transitional phrase ‘consisting essentially of’ limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the claimed invention.

The phrase ‘carrier gas’ means a gas that is introduced into a DART source which generates the metastable neutral species which are used to ultimately form gas phase ions of analytes, either by directly interacting with analyte molecules or through the action of the metastable neutral species on an intermediate species.

The phrase ‘molecular ion’ means M⁺. or M⁻. as an ionized species. The phrase predominantly molecular ion species means that the measured mass spectrum contains the M⁺. or M⁻. species with a relative intensity of greater than approximately sixty (60) percent, where approximately is ±ten (10) percent.

The phrase ‘protonated molecule ion’ means [M+H]⁺ as an ionized species. The phrase ‘predominantly protonated molecule ion species’ means that the measured mass spectrum contains the [M+H]⁺ species with a relative intensity of greater than approximately sixty (60) percent, where approximately is ±ten (10) percent.

The phrase ‘deprotonated molecule ion’ means [M−H]⁻ as an ionized species. The phrase ‘predominantly deprotonated molecule ion species’ means that the measured mass spectrum contains the [M−H]⁻ species with a relative intensity of greater than approximately sixty (60) percent, where approximately is ±ten (10) percent.

The phrase ‘proton transfer’ when referring to dopant DART means that the metastable DART gas can ionize (without transferring a proton) a dopant, a sample molecule with a suitably low ionization energy or a background molecule, and these species can undergo ion molecule reactions ultimately resulting in the transfer of a proton to an analyte.

The phrase ‘Direct Analysis in Real Time’ abbreviated as ‘DART’ means an ionization process with a carrier gas whereby a discharge is used to generate an excited metastable neutral carrier gas species which can be directed at an analyte to ionize the analyte.

The phrases ‘helium DART’, ‘nitrogen DART’, ‘neon DART’, ‘argon DART’, ‘krypton DART’ and ‘xenon DART’ mean a DART ionization process where the carrier gas is helium, nitrogen, neon, argon, krypton and xenon gases respectively.

The symbol ‘He*’ means an excited metastable helium species. The symbol ‘N₂*’ means an excited metastable nitrogen species. The symbol ‘Ne*’ means an excited metastable neon species. The symbol ‘Ar*’ means an excited metastable argon species. The symbol ‘Kr*’ means an excited metastable krypton species. The symbol ‘Xe*’ means an excited metastable xenon species.

The word or phrases ‘conventional’, ‘conventional DART’ or ‘conventional DART source’ mean an ionization process with a carrier gas selected from one or more of helium, nitrogen and neon gases that when interacting directly with an analyte produce predominantly either protonated molecule ion species (positive mode) or deprotonated molecule ion species (negative mode). By definition, a conventional DART source generates one or more of He*, N₂* and Ne* containing carrier gases to interact with the analyte.

The phrase ‘argon DART’ means a DART ionization process with an argon carrier gas. The phrase ‘krypton DART’ means a DART ionization process with a krypton carrier gas. The phrase ‘xenon DART’ means a DART ionization process with an xenon carrier gas. By definition, an argon DART source generates an Ar* containing carrier gas. By definition, a krypton DART source generates a Kr* containing carrier gas. By definition, a xenon DART source generates a Xe* containing carrier gas.

The phrase ‘efficient dopant’ means a dopant that produces a species able to act as a donor (positive mode) or acceptor (negative mode) in a charge exchange and/or proton transfer reaction with the analyte of interest.

The phrase ‘dopant-assisted DART’ or ‘dopant DART’ means an ionization process where an efficient dopant is introduced into the carrier gas. In various embodiments of the invention, an efficient dopant is a compound having an ionization energy lower than the internal energy of the metastable carrier gas that is suitable for one or both charge exchange and proton transfer to analyte compounds.

The phrase ‘dopant-assisted argon DART’ means an ionization process where the carrier gas is argon and an efficient dopant is introduced into the Ar*. In various embodiments of the invention, an efficient dopant is a compound having an ionization energy lower than the internal energy of Ar* that is suitable for one or both charge exchange and proton transfer to analyte compounds.

The phrase ‘ion activation’ means collisionally activated dissociation, collision induced dissociation, in source fragmentation, ion metastable fragmentation, ion surface collisions, ion induced dissociation, photodissociation, ion neutral collisions, ion electron collisions, ion electron collisions, electron capture dissociation or function switching. Fragment ions can be formed from a precursor by exciting the precursor either by way of collision or otherwise transferring energy to cause bond scission in the precursor.

The word ‘simultaneously’ is used to refer to a process where the formation of two different species occurs at relatively the same, but not the exact same time. Simultaneous formation of two species can be contrasted with a process where predominantly a first species is formed and then at a later time at least one (1) second after predominantly a second species is formed.

The word ‘deployed’ means attached, affixed, adhered, inserted, located or otherwise associated.

The phrase ‘mass spectrometer system’ means an instrument selected from the group consisting of a sector, a double focusing sector, a single quadrupole, a triple quadrupole, a quadrupole ion trap (Paul trap), a linear ion trap, a rectilinear ion trap, a cylindrical ion trap, an ion cyclotron resonance trap, an orbitrap, and a time of flight mass spectrometer. A mass spectrometer system is able to isolate and excite or otherwise generate fragment ions of an analyte (precursor) species.

The phrase ‘trapped ion device’ includes a quadrupole ion trap, a linear ion trap, a rectilinear ion trap, a cylindrical ion trap, an ion cyclotron resonance trap, and an orbitrap.

The phrase ‘mass filter’ means a mode, a selection, or a scan carried out using a mass spectrometer system.

The word ‘cell’ means a vessel used to contain one or more of a homogeneous or heterogeneous liquid, gas or solid sample.

The word ‘screen’ means two or more connected filaments, a mesh, a grid or a sheet. In various embodiments of the present invention, a screen includes three or more connected filaments where at least one filament is approximately orthogonal to one other filament. A screen thickness is greater than approximately 20 micrometer and less than approximately one centimeter, where approximately is ±twenty (20) percent. A metallic screen is a screen where the filaments, mesh, grid or sheet block magnetic coupling.

The word ‘directing’ means causing a carrier gas and or ions formed in part by the carrier gas to one or both impinge and interact with a sample.

The word ‘combining’ means using two or more extracted pieces of information observed in measuring the mass to charge ratio of ions formed from a sample to determine one or more chemical features of the sample.

The phrase ‘chemical feature of a sample’ means the elemental composition, chemical structure or part thereof.

The word ‘measuring’ means using a mass spectrometer system and/or a mass filter to extract one or more pieces of information observed in measuring the mass to charge ratio of ions formed from a sample.

The phrases ‘metastable carrier gas’, ‘metastable neutral carrier gas’, ‘metastable DART gas’ or ‘metastable DART carrier gas’ mean a gas containing an excited metastable species that is suitable for one or both charge exchange and proton transfer to one or more analyte compounds. Gases having an appropriate internal energy to act as carrier gases include helium, nitrogen, neon, argon, krypton, and xenon.

The phase ‘conventional carrier gas’ means the carrier gas used with a conventional DART source.

The phrase ‘intact ion’ or ‘intact molecule ion’ means one or more of a protonated molecule ion, a deprotonated molecule ion, a molecular ion, an adduct molecule positive ion and an adduct molecule negative ion.

The phrase ‘dopant DART source’ means one or more of an argon DART source, a krypton DART source and a xenon DART source.

The phrase ‘dopant carrier gas’ means the carrier gas used with a dopant DART source.

The phrases ‘metastable dopant carrier gas’, is produced by introducing a dopant carrier gas into a dopant DART source.

The phrase ‘dopant ions’ means an ion generated by the interaction of a dopant with a dopant carrier gas.

A ‘filament’ means a wire with a diameter greater than approximately 20 micrometer and less than approximately one centimeter, where approximately is ±twenty (20) percent.

A gas ion separator means the device described in U.S. Pat. No. 7,700,913, which disclosure is herein explicitly incorporated by reference in its entirety.

A ‘metal’ comprises one or more elements consisting of lithium, beryllium, boron, carbon, nitrogen, oxygen, sodium, magnesium, aluminum, silicon, phosphorous, sulfur, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, cesium, barium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, polonium, francium and radium.

In the following description, various aspects of the present invention are described. However, it will be apparent to those skilled in the art that the present invention can be practiced with only some or all aspects of the present invention. For purposes of explanation, specific numbers, materials, and configurations are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention can be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the present invention.

Parts of the description are presented in data processing terms, such as data, selection, retrieval, generation, and so forth, consistent with the manner commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. As is well understood by those skilled in the art, these quantities (data, selection, retrieval, generation) can take the form of electrical, magnetic, or optical signals capable of being stored, transferred, combined, and otherwise manipulated through electrical, optical, and/or biological components of a processor and its subsystems.

Various operations are described as multiple discrete steps in turn, in a manner that is helpful in understanding the present invention; however, the order of description should not be construed as to imply that these operations are necessarily order dependent.

Various embodiments are illustrated in terms of exemplary classes and/or objects in an object-oriented programming paradigm. It will be apparent to one skilled in the art that the present invention can be practiced using any number of different classes/objects, not merely those included here for illustrative purposes.

Aspects of the invention are illustrated by way of example and not by way of limitation in the Figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to ‘an’ or ‘one’ embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

Argon has not been widely used in DART because the lower internal energy of Ar* does not result in the formation of water ions. Therefore, argon can only undergo Penning ionization with analytes having relatively low ionization energies. Typically, only samples with ionization energies lower than the internal energy of the metastable argon ³P₂and ³P₀states (11.55 and 11.72 eV, respectively) can be ionized. Argon DART has been used to selectively ionize melamine contamination in powdered milk. The initial step involved Ar* Penning ionization of acetyl acetone (AcAc). This was then followed by a series of proton transfer reactions between protonated AcAc and pyridine. Finally, the protonated pyridine reacted with the melamine present in the milk.

Penning ionization and photoionization are closely related phenomena. The internal energy of the excited-state neutral in Penning ionization, or the photon energy in photoionization, determines the reagent ions that play a role in subsequent atmospheric pressure ion-molecule reactions in DART. In an embodiment of the present invention, DART can be operated with argon gas by adding an efficient dopant to the metastable DART gas stream as shown in FIG. 7.

An AccuTOF-LP 4G (JEOL Ltd., Akishima, Japan) time-of-flight mass spectrometer equipped with a Direct Analysis in Real Time (DART-SVP) ion source (IonSense Inc., Saugus, Mass.) was used for all measurements. Unless otherwise noted, mass spectra were stored at a rate of one spectrum per second and the voltages on the atmospheric pressure interface (API) were: orifice-1=20V, and orifice-2=ring lens=5V. The RF ion guide voltage was set to 70 V to observe low-mass atmospheric background ions and dopant reagent ions (m/z 10-800), or set to 550 V for sample measurements (m/z 60-800). The monoamine-terminated poly(ethylene oxide) polymer Jeffamine M-600 (Huntsman, The Woodlands, Tex.) was measured in each data file as a reference standard for exact mass measurements, and perfluorotributylamine (PFTBA) was used as a mass reference standard for negative-ion measurements.

Acetone (Sigma-Aldrich Chromasolv® 99.9%), toluene (J. T. Baker, Ultra-Resi-Analyzed, 99.7%), and anisole (Sigma-Aldrich Reagent-Plus, 99%) were used as supplied without further treatment. Argon (Matheson, Grade 5.0) and helium (Matheson, Grade 4.7) were used as carrier gases as supplied without further treatment. Successive dilutions of a mixture of unlabeled Polycyclic Aromatic Hydrocarbons (PAH) (Cambridge Isotope Laboratories, PAH Native Standard Mixture ES-5438) in toluene were carried out to evaluate sensitivity and detection limits.

Dopants were infused at a rate of 9 μL min⁻¹through deactivated fused silica tubing by using a syringe pump (WPI sp200i, World Precision Instruments, Shanghai, China). This value was determined by varying the flow rate from 1 μL min⁻¹to 14 μL min⁻¹. Beyond 9 μL min⁻¹, there was no significant change in the signal intensity for the anisole molecular ion.

Forceps mounted on a stand were used to position the exit tip of the fused silica directly in front of the ceramic insulator at the metastable DART gas exit. The liquid dopants evaporated directly into the metastable DART gas stream. Unless otherwise noted, dopant-assisted argon DART mass spectra reported herein were measured by using 0.5% anisole in toluene as the efficient dopant. As a result, this efficient dopant mixture can be used for the analysis of solutions in methanol without requiring prior drying of the sample. In various embodiments of the invention, dopants include chlorobenzene, bromobenzene, 2, 4-difluoroanisole, and 3-(trifluoromethyl)anisole.

FIG. 6 shows a schematic of the DART source 600 with the DART gun 610 position relative to orifice-1 620. The DART gun 610 was positioned approximately 1 cm from the apex of the mass spectrometer sampling orifice (“orifice-1”) 620, where approximately is ±thirty (30) percent. The dopant was introduced through a feed 530 positioned in front of the DART gun. Unless otherwise noted the DART gas heater was set to 300° C. Argon and helium can be introduced to the DART controller through the same gas line. The gas selection was determined by opening and closing the valves on the gas supply cylinders. Supply lines to the DART were purged with the valves on both gas cylinder lines closed when switching between helium and argon. The DART was set to standby mode with nitrogen purge gas when not actively measuring samples. Flow regulators in the DART SVP controller set the gas flow rate for all gases to one (1) liter per minute. In various embodiments of the invention, ion activation can be carried out with tandem mass spectrometry (MS/MS) systems or with in-source fragmentation. In various embodiments of the invention, in-source fragmentation can be accomplished by adjusting the voltages in the atmospheric pressure interface to increase the ion kinetic energies as they collide with neutral gas molecules in the interface region (function switching in an AccuTOF). The specific fragments observed in tandem mass spectrometry or in-source fragmentation vary with collision energy. For the examples given here, the term ‘orifice-1 voltage’ refers to the collision energy for in-source fragmentation of ions produced by DART ionization.

Samples were measured by pipetting 3 μL of sample solutions onto the sealed end of a melting point tube, allowing the solvent to dry, and then suspending the sealed end of the tube directly in front of the metastable DART gas exit and the fused silica capillary used to introduce the dopant.

Polyethers such as poly(ethylene oxide) also known as polyethylene glycol or “PEG” are commonly used as reference standards for mass calibration for DART. Toluene or toluene/anisole is not an efficient dopant for the analysis of polyethers with argon DART. However, Jeffamine M-600 (Huntsman), a monoamine-terminated poly(propylene oxide), is efficiently ionized, producing abundant protonated molecule species when analyzed under these conditions. The anisole molecular ion was included together with the Jeffamine [M+H]⁺ peaks in the calibration to provide a reference peak at m/z 108.05751.

No peaks were observed in negative-ion mode with argon DART for PEG or for perfluoropropyl ether (Fomblin Y). The latter is a reference standard for negative-ion mode measurements with helium DART. In various embodiments of the invention, argon DART analysis of perfluorotributylamine (PFTBA) generated a spectrum containing a set of species that can be used as reference standards.

FIG. 7A shows a schematic of an instrument configuration 700 where the DART source 714 can be used as a conventional DART source initially (or subsequently) which is supplied with a conventional carrier gas (for example one or more of He, Ne or N₂gases) through tubing 703, valve 725 and through tubing 707 to the DART source 714 to direct the metastable DART gas (for example excited atoms) (not shown) toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732. In an embodiment of the invention, the DART source 714 can be used as a dopant DART source subsequently (or initially) which is supplied with dopant carrier gas (for example one or more of Ar, Xe or Kr gases) through tubing 704, valve 725 and through tubing 707 to the DART source 714 to direct the metastable dopant carrier gas (not shown) to interact with one or more dopants introduced from one or more reservoirs 754, 755 through tubing 709, 702, valve 727 and through tubing 706 to interact with the excited atoms (not shown) and direct the dopant ions toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732. In an embodiment of the invention, the analyzer entrance 732 can be an atmospheric pressure interface. In an alternative embodiment of the invention, the analyzer entrance 732 can incorporate a gas ion separator.

FIG. 7B shows a schematic of an instrument configuration 700 where conventional DART source 714 can be used initially, subsequently, or simultaneously supplied with a conventional carrier gas (for example one or more of He, Ne or N₂gases) through tubing 704 to the DART source 714 to direct metastable DART gas (for example excited atoms) (not shown) toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732. In an embodiment of the invention, the dopant DART source 715 supplied with dopant carrier gas (for example one or more of Ar, Xe or Kr gases) through tubing 705 can be used subsequently, initially or simultaneously, to direct the metastable dopant carrier gas (not shown) to interact with dopant introduced from reservoir 754 through tubing 709, valve 727 and through tubing 706 to form dopant ions (not shown) directed toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732.

FIG. 7C shows a schematic of an instrument configuration 700 where the DART source 714 can be used as a conventional DART source initially (or subsequently) which is supplied with a conventional carrier gas (for example one or more of He, Ne or N₂gases) through tubing 703, valve 725 and through tubing 707 to the DART source 714 to direct metastable DART gas (for example excited atoms) (not shown) toward the sample 750. In an embodiment of the invention, the DART source 714 can be used as a dopant DART source subsequently (or initially) which is supplied with dopant carrier gas (for example one or more of Ar, Xe or Kr gases) through tubing 704, valve 725 and through tubing 707 to the DART source 714 to direct the metastable dopant carrier gas (not shown) to interact with one or more dopants introduced from reservoirs 754, 755 through tubing 709, 702, valves 727, 728 and through tubing 706, 707 to interact with the excited atoms (not shown) and direct the dopant ions toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732.

FIG. 7D shows a schematic of an instrument configuration 700 where conventional DART source 714 can be used initially, subsequently, or simultaneously which is supplied with a conventional carrier gas (for example one or more of He, Ne or N₂gases) through tubing 704 to the DART source 714 to direct metastable DART gas (for example excited atoms) (not shown) which interact with a dopant supplied from reservoir 755 through tubing 708, valve 726 and through tubing 707 to form dopant ions (not shown) directed toward the sample 750. In an embodiment of the invention, the dopant DART source 715 supplied with dopant carrier gas (for example one or more of Ar, Xe or Kr gases) through tubing 705 can be used subsequently, initially or simultaneously, to direct the metastable dopant carrier gas (not shown) to interact with dopant introduced from reservoir 754 through tubing 709, valve 727 and through tubing 706 to form dopant ions (not shown) directed toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732.

FIG. 7E shows a schematic of an instrument configuration 700 where conventional DART source 714 can be used initially, subsequently, or simultaneously which is supplied with a conventional carrier gas (for example one or more of He, Ne or N₂gases) through tubing 704 to the DART source 714 to direct metastable DART gas (for example excited atoms) (not shown) which interact with a dopant supplied from reservoir 755 through tubing 708, valve 726 and through tubing 707 to form dopant ions (not shown) directed toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732. In an embodiment of the invention, the dopant DART source 715 supplied with dopant carrier gas (for example one or more of Ar, Xe or Kr gases) through tubing 705 can be used subsequently, initially or simultaneously, to direct the metastable dopant carrier gas (not shown) to interact with dopant introduced from reservoirs 754, 753 through tubing 709, 701, valves 727, 728 and through tubing 706, 702 to form dopant ions (not shown) directed toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732.

FIG. 7F shows a schematic of an instrument configuration where the DART source 714 can be used as a conventional DART source initially (or subsequently) which is supplied with a conventional carrier gas (for example one or more of He, Ne or N₂gases) through tubing 703, valve 725 and through tubing 707 to the DART source 714 to direct metastable DART gas (for example excited atoms) (not shown) toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732. In an embodiment of the invention, the DART source 714 can be used as a dopant DART source subsequently (or initially) which is supplied with dopant carrier gas (for example one or more of Ar, Xe or Kr gases) through tubing 704, valve 725 and through tubing 707 to the DART source 714 to direct the metastable dopant carrier gas (not shown) to interact in mixing chamber 748 with one or more dopants introduced from reservoirs 754, 755 through tubing 709, 702, valves 727, 728 and through tubing 706, 707 to form dopant ions (not shown) directed toward the sample 750 and thereafter sample ions (not shown) which enter the analyzer entrance 732.

FIG. 7G shows a schematic of an instrument configuration 700 where conventional DART source 714 is used initially, subsequently, or simultaneously supplied with a conventional carrier gas (for example one or more of He, Ne or N₂gases) through tubing 704 to the DART source 714 to direct metastable DART gas (for example excited atoms) (not shown) which optionally interact with a dopant supplied from reservoir 755 through tubing 708, valve 726 and through tubing 707 to either direct the excited atoms (not shown) and/or dopant ions (not shown) toward the sample 750 and thereafter sample ions which enter the analyzer entrance 732. In an embodiment of the invention, the dopant DART source 715 supplied with dopant carrier gas (for example one or more of Ar, Xe or Kr gases) through tubing 705 is used subsequently, initially or simultaneously, to direct the metastable dopant carrier gas (not shown) to interact in mixing chamber 748 with one or more dopants introduced from reservoirs 754, 753 through tubing 709, 701, valves 727, 728 and through tubing 706, 702 to form dopant ions (not shown) directed toward the sample 750 and thereafter sample ions (not shown) which enter the analyzer entrance 732.

Example 1

No ions are observed in the background spectrum covering the mass range corresponding to m/z 10-800 when argon was used without dopants (FIG. 1A). This suggests that argon ions do not play a role in DART ionization with argon gas, and provides support for a proposed ionization mechanism involving metastable argon atoms. In various embodiments of the invention, a gas with a sufficiently low ionization energy can be introduced to generate analyte ions.

FIG. 1A shows a background positive-ion argon DART mass spectra with no dopant and the y-axis scale magnified by 833. FIG. 1B shows a background positive-ion dopant-assisted argon DART mass spectra with an acetone dopant, with m/z 59, 76 and 117 identified, where the m/z of the major ions observed are identified in Table II. FIG. 1C shows a background positive-ion dopant-assisted argon DART mass spectrum with a toluene dopant, with m/z 69, 92, 93, 108, 109, and 129 identified, where the m/z of the major ions observed are identified in Table III. FIG. 1D shows a background positive-ion dopant-assisted argon DART mass spectrum with a toluene and 0.5% anisole dopant, with m/z 94 and 108 identified, where the m/z of the major ions observed are identified in Table IV. The chlorobenzene dopant-assisted argon DART mass spectrum (FIG. 1E) shows the chlorobenzene molecular ion as the base peak (112), with m/z 94 and 112 identified, where the m/z of the major ions observed are identified in Table V. In various embodiments of the invention, the spectra (FIG. 1B, FIG. 1C, FIG. 1D and FIG. 1E) contain peaks corresponding to molecular ions, protonated molecules, and small peaks that are possible ion-molecule reaction products. In particular, the acetone spectrum (FIG. 1B) shows protonated acetone and proton-bound dimer and a small acetone ammonium adduct [M+NH₄]⁺ species. Trace environmental contamination from anisole is observed in the toluene spectrum (FIG. 1C). The toluene and anisole spectrum (FIG. 1D) shows traces of benzene, phenol, and methylated anisole and some impurities in the solvent, the plumbing, and/or the environment. The chlorobenzene mass spectrum (FIG. 1E) shows phenol (an impurity in the chlorobenzene) and anisole (from residual traces in the dopant plumbing) molecular ions.

Example 2

In various embodiments of the invention, all of the PAHs in the mixture (Table I) were detected as molecular ions (see FIG. 2) by analyzing the PAH sample using dopant-assisted argon DART with the toluene/anisole dopant. An additional component was observed at m/z 278.10941, which differs from the calculated m/z for the elemental composition C₂₂H₁₄by 0.14 mmu. This is labeled on the mass spectrum as dibenz[a]anthracene, although it could be one or more of the isomeric C₂₂H₁₄PAHs (see Table I).

FIG. 2A shows the dopant-assisted argon DART mass spectrum for the solution at a concentration of 10 ppm (for the components present as a single isomer), with m/z 108, 202 and 252 identified, where the m/z of the major ions observed are identified in Table VI. FIG. 2B shows the dopant-assisted argon DART mass spectrum for a concentration of 500 ppb, with m/z 192 and 252 identified, where the m/z of the major ions observed are identified in Table VII. FIG. 2C shows the mass spectrum for the 5 ppb solution, with m/z 166.0773 identified. With the exception of naphthalene, which was obscured at the 5 ppb level by an unresolved background interference at m/z 128.078, at the 5 ppb level, all of the PAHs can be detected and separated at the mass spectrometer resolving power of 10,000 full width half maximum (FWHM) from the chemical background. Naphthalene was barely detectable at 10 ppb but was clearly detected at a concentration of 50 ppb. The peak areas for all PAHs normalized to the internal standard (9-methyl anthracene) showed a linear response with the correlation coefficient R²=0.99 up to a concentration of 5 ppm.

Example 3

A 10 μL sample of diesel fuel purchased at a local convenience store was diluted in 1 mL of hexane. 3 μL of this hexane solution was deposited onto the sealed end of a melting point tube, and the tube was positioned in the metastable DART gas stream. FIG. 3A shows the mass spectrum obtained by using dopant-assisted argon DART with the toluene/anisole dopant solution, with m/z 210 and 391 identified, where the m/z of the major ions observed are identified in Table VIII. In various embodiments of the invention, molecular ions were observed at even-m/z peaks for aromatic species such as alkyl naphthalenes (C₁₀H₈+nCH₂). The helium-DART analysis (FIG. 3B) of the same sample shows a more complex mass spectrum with both protonated molecules (odd-m/z peaks) and molecular ions (even-m/z peaks) as well as abundant peaks representing protonated fatty acid methyl esters (FAMES) from biodiesel species, with m/z 295 and 312 identified, where the m/z of the major ions observed are identified in Table IX. In various embodiments of the invention, the dopant-assisted argon DART mass spectra of complex mixtures are therefore easier to interpret, because of the higher selectivity which can be varied by the choice of dopants. In various embodiments of the invention, it is possible to use argon DART to obtain information on complex mixtures.

Example 4

The feasibility of obtaining negative-ion mass spectra with dopant-assisted argon DART was demonstrated for 2, 4, 6-trinitrotoluene (TNT). For this experiment, the DART exit electrode potential was set to minus fifty volts (−50V) and the mass spectrometer polarities were set to negative-ion mode by loading a previously stored negative-ion tune condition. The atmospheric pressure interface potentials (orifice-1, ring lens, and orifice-2) were set to −20V, −5V and −5V, respectively.

Electrons formed when the dopant undergoes Penning ionization are captured by the analyte and/or atmospheric oxygen. Oxygen anions can react with suitable analytes to extract a proton. The negative-ion background dopant-assisted argon DART mass spectrum observed (see FIG. 4A) also shows some ions that are commonly observed in the negative-ion helium DART background (NO₂⁻, C₂H₃O₂⁻, CO₃⁻, HCO₃⁻), a trace of Cl⁻, and several peaks that may result from impurities in the toluene/anisole dopant mixture, with m/z 46, 60 and 121 identified, where the m/z of the major ions observed are identified in Table X.

In various embodiments of the invention, the dopant-assisted argon DART mass spectrum of TNT shown in FIG. 4B, with m/z 121, 226 and 243 identified, where the m/z of the major ions observed are identified in Table XI, is complementary to that obtained by using helium DART gas (FIG. 4C), with m/z 227 and 243 identified, where the m/z of the major ions observed are identified in Table XII. Both spectra show peaks corresponding to the molecular ion and the deprotonated molecule as well as characteristic losses of OH and NO to produce the C₇H₅N₂O₅⁻ and C₇H₄N₃O⁻ fragment ions respectively. A peak was observed in both mass spectra at m/z 243.014, assigned as 3-methyl-2, 4, 5-trinitrophenol, an impurity or degradation product in the sample. In various embodiments of the invention, the deprotonated molecule can be observed at a higher relative abundance in the dopant-assisted argon DART mass spectrum than in the helium DART mass spectrum.

Example 5

Δ-9 tetrahydrocannabinol (THC) and cannabidiol (CBD) are isomeric compounds that are present in marijuana. THC and CBD exhibit different electron ionization mass spectra, but the fragment-ion mass spectra produced by collision-induced fragmentation of the protonated molecules are indistinguishable.

In various embodiments of the invention, the positive-ion mass spectra observed for dopant-assisted argon DART ionization of THC (FIG. 5A), with m/z 314 and 330 identified, where the m/z of the major ions observed are identified in Table XIII, and CBD (FIG. 5B), with m/z 120, 195, 314 and 330 identified, where the m/z of the major ions observed are identified in Table XIV, with orifice 1 set to 20V are characterized by both molecular ions M⁺. and protonated molecules [M+H]⁺. In various embodiments of the invention, the in-source fragmentation mass spectra measured with orifice-1 set to 60V of dopant-assisted argon DART ionization of THC (FIG. 5C), with m/z 193, 231, 299 and 315 identified, where the m/z of the major ions observed are identified in Table XV, and CBD (FIG. 5D), with m/z 193, 231, 299 and 315 identified, where the m/z of the major ions observed are identified in Table XVI, are clearly different. In various embodiments of the invention, the in-source fragmentation mass spectra measured with orifice-1 set to 90V of dopant-assisted argon DART ionization of THC (FIG. 5E), with m/z 81, 123, 193, 231, 299 and 313 identified, where the m/z of the major ions observed are identified in Table XVII, and CBD (FIG. 5F), with m/z 81, 123, 174, 193, 231 and 299 identified, where the m/z of the major ions observed are identified in Table XVIII, are also very different. In various embodiments of the invention, dopant-assisted argon DART can be used to assess the relative concentrations of THC and CBD in a mixture. Methanol solutions were prepared with both THC and CBD in ratios of 1:0, 2:1, 1:1, 1:2, and 0:1, respectively. Ratios of several fragment ions were compared against THC concentration. The best linearity was obtained for the orifice-1=90V mass spectra by plotting the sum of the relative abundances of the fragments at m/z 217 and m/z 299 divided by the relative abundance of m/z 207 against percent THC in each mixture. The measurement was repeated twice, giving a correlation coefficient or R²=0.995 each time. In alternative embodiments of the invention, isotopically labeled internal standards can be used for quantitative analysis.

In various embodiments of the invention, dopant-assisted DART offers an alternative method for operating a DART ion source and provides complementary information to conventional DART. Other efficient dopants include chlorobenzene, bromobenzene, 2,4-difluoroanisole, and 3-(trifluoromethyl)anisole.

The present invention is directed to a method of Direct Analysis in Real Time (DART) analysis with argon gas in the presence of dopants to the gas stream exiting the DART source. Charge-exchange and proton transfer reactions are observed with the addition of dopants such as toluene, anisole, and acetone. Polycyclic aromatic hydrocarbons can be detected as molecular ions at concentrations in the low part-per-billion range by using a solution of 0.5% anisole in toluene as a dopant. Dopant-assisted argon DART analysis of a diesel fuel sample with the same dopant mixture showed a simpler mass spectrum than obtained by using helium DART. The dopant-assisted argon DART mass spectrum was dominated by molecular ions for aromatic compounds, whereas the helium DART mass spectrum showed both molecular ions and protonated molecules. Further, positive ions produced by argon DART ionization for THC and CBD showed distinctive fragment-ion mass spectra. This differs from helium DART, where protonated THC and CBD produce identical fragment-ion mass spectra.

In the absence of a dopant, ‘helium DART’, ‘nitrogen DART’, and ‘neon DART’ interacting with an analyte produce predominantly protonated molecule ion species of the analyte or predominantly deprotonated molecule ion species of the analyte. Similarly, in the absence of a dopant, ‘argon DART’ interacting with an analyte produce predominantly protonated molecule ion species of the analyte or predominantly deprotonated molecule ion species of the analyte. Accordingly, the mass spectrum shown in FIG. 1B contains protonated acetone molecule ion species, as there was no analyte and the acetone added as a dopant has a sufficiently low ionization energy for the Ar* to form [M+H]⁺ of the acetone dopant molecules.

In an embodiment of the present invention, in the presence of an efficient dopant, ‘argon DART’ interacting with an analyte produces predominantly molecular ion species of the analyte.

In an embodiment of the present invention, a mixture of carrier gases produce DART spectra based on the species formed with the greatest ionization efficiency. That is in an embodiment of the present invention, a mixture of helium and argon carrier gasses introduced with an efficient dopant to ionize an analyte produce a mass spectrum where the intact species is predominantly molecular ion species of the analyte.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a DART source to generate one or more ions of the sample, an argon DART source to generate a plurality of ions of the sample, a mass spectrometer for measuring a first mass spectrum of one or both the one or more ions and the plurality of ions, a mass spectrometer system for generating one or more fragment ions from the plurality of ions and a mass spectrometer for measuring a second mass spectrum of the one or more fragment ions, where the argon DART source includes a valve to add a dopant, where the dopant is one or more compounds selected from the group consisting of anisole, toluene, acetone, chlorobenzene, bromobenzene, 2, 4-difluoroanisole, and 3-(trifluoromethyl)anisole.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a DART source to generate one or more ions of the sample, an argon DART source to generate a plurality of ions of the sample, a mass spectrometer for measuring a first mass spectrum of one or both the one or more ions and the plurality of ions, a mass spectrometer system for generating one or more fragment ions from the plurality of ions and a mass spectrometer for measuring a second mass spectrum of the one or more fragment ions, where the argon DART source includes a valve to add a dopant, where the dopant is one or more compounds having an ionization energy lower than the internal energy of metastable argon that is suitable for one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a DART source to generate one or more ions of the sample, an argon DART source to generate a plurality of ions of the sample, a mass spectrometer for measuring a first mass spectrum of one or both the one or more ions and the plurality of ions, a mass spectrometer system for generating one or more fragment ions from the plurality of ions and a mass spectrometer for measuring a second mass spectrum of the one or more fragment ions, where the one or more fragment ions are formed from ion activation, where the one or more fragment ions are formed from one or more methods selected from the group consisting of collisionally activated dissociation, collision induced dissociation, in source fragmentation, ion surface collisions, ion induced dissociation, photodissociation, ion neutral collisions, ion electron collisions, ion electron collisions, electron capture dissociation and function switching.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a DART source to generate one or more ions of the sample, an argon DART source to generate a plurality of ions of the sample, a mass spectrometer for measuring a first mass spectrum of one or both the one or more ions and the plurality of ions, a mass spectrometer system for generating one or more fragment ions from the plurality of ions and a mass spectrometer for measuring a second mass spectrum of the one or more fragment ions, where the one or more fragment ions are formed from ion activation, where the one or more fragment ions are generated by function switching with an orifice-1 voltage set between a lower limit of approximately 10 V and an upper limit of approximately 250 V, where approximately is ±ten (10) percent.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a DART source to generate one or more ions of the sample, an argon DART source to generate a plurality of ions of the sample, a mass spectrometer for measuring a first mass spectrum of one or both the one or more ions and the plurality of ions, a mass spectrometer system for generating one or more fragment ions from the plurality of ions and a mass spectrometer for measuring a second mass spectrum of the one or more fragment ions, where the one or more fragment ions are formed from ion activation, where the one or more fragment ions are generated by function switching with an orifice-1 voltage set between a lower limit of approximately 20 V and an upper limit of approximately 200 V, where approximately is ±ten (10) percent.

In an embodiment of the present invention, an ionization system for identifying a plurality of analytes present in a sample comprising a DART source, an argon DART source, a valve for introducing a dopant into the argon DART source and a mass spectrometer system for fragmenting ions generated from the sample ionized with the argon DART source, where the dopant is one or more compounds selected from the group consisting of anisole, toluene, acetone, chlorobenzene, bromobenzene, 2, 4-difluoroanisole, and 3-(trifluoromethyl)anisole.

In an embodiment of the present invention, an ionization system for identifying a plurality of analytes present in a sample comprising a DART source, an argon DART source, a valve for introducing a dopant into the argon DART source and a mass spectrometer system for fragmenting ions generated from the sample ionized with the argon DART source, where the dopant is selected from one or more compounds having an ionization energy lower than the internal energy of a metastable argon species formed by the argon DART source, where the metastable argon species is capable of one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a method for determining a plurality of analytes present in a sample comprising the steps of directing a helium DART source at the sample, measuring a mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions of one or more of the plurality of analytes, directing an argon DART source at the sample, measuring a mass spectrum containing a molecular ion of one or more of the plurality of analytes and combining the mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions with the mass spectrum containing a molecular ion to determine the plurality of analytes present in a sample, where the helium DART source and argon DART source simultaneously generate ions of the sample.

In an embodiment of the present invention, a method for determining a plurality of analytes present in a sample comprising the steps of directing a helium DART source at the sample, measuring a mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions of one or more of the plurality of analytes, directing an argon DART source at the sample, measuring a mass spectrum containing a molecular ion of one or more of the plurality of analytes and combining the mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions with the mass spectrum containing a molecular ion to determine the plurality of analytes present in a sample, where a single DART source is used to generate ions by switching between helium and argon gases.

In an embodiment of the present invention, a method for determining a plurality of analytes present in a sample comprising the steps of directing a helium DART source at the sample, measuring a mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions of one or more of the plurality of analytes, directing an argon DART source at the sample, measuring a mass spectrum containing a molecular ion of one or more of the plurality of analytes and combining the mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions with the mass spectrum containing a molecular ion to determine the plurality of analytes present in a sample, further comprising generating fragment ions of one or more of the molecular ions.

In an embodiment of the present invention, a method for determining a plurality of analytes present in a sample comprising the steps of directing a helium DART source at the sample, measuring a mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions of one or more of the plurality of analytes, directing an argon DART source at the sample, measuring a mass spectrum containing a molecular ion of one or more of the plurality of analytes and combining the mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions with the mass spectrum containing a molecular ion to determine the plurality of analytes present in a sample, where at least the step of measuring a mass spectrum containing a molecular ion includes adding a dopant.

In an embodiment of the present invention, a method for determining a plurality of analytes present in a sample comprising the steps of directing a helium DART source at the sample, measuring a mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions of one or more of the plurality of analytes, directing an argon DART source at the sample, measuring a mass spectrum containing a molecular ion of one or more of the plurality of analytes and combining the mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions with the mass spectrum containing a molecular ion to determine the plurality of analytes present in a sample, where at least the step of measuring a mass spectrum containing a molecular ion includes adding a dopant, where the dopant is one or more compounds selected from the group consisting of anisole, toluene, acetone, chlorobenzene, bromobenzene, 2, 4-difluoroanisole, and 3-(trifluoromethyl)anisole.

In an embodiment of the present invention, a method for determining a plurality of analytes present in a sample comprising the steps of directing a helium DART source at the sample, measuring a mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions of one or more of the plurality of analytes, directing an argon DART source at the sample, measuring a mass spectrum containing a molecular ion of one or more of the plurality of analytes and combining the mass spectrum containing one or both protonated molecule ions and deprotonated molecule ions with the mass spectrum containing a molecular ion to determine the plurality of analytes present in a sample, where at least the step of measuring a mass spectrum containing a molecular ion includes adding a dopant, where the dopant is one or more compounds having an ionization energy lower than the internal energy of metastable argon that is suitable for one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a source to generate predominantly protonated molecule ions of the sample, a source including a carrier gas and a dopant to generate predominantly molecular ions of the sample, a mass spectrometer for recording a first mass spectrum of the ions generated from the sample, a mass spectrometer system for fragmenting intact molecular ions and a mass spectrometer for recording a second mass spectrum of one or more fragment ions, where the carrier gas is argon, where the dopant is selected from one or more compounds having an ionization energy lower than the internal energy of a metastable argon species formed from the carrier gas, where the metastable argon species is capable of one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a source to generate predominantly protonated molecule ions of the sample, a source including a carrier gas and a dopant to generate predominantly molecular ions of the sample, a mass spectrometer for recording a first mass spectrum of the ions generated from the sample, a mass spectrometer system for fragmenting intact molecular ions and a mass spectrometer for recording a second mass spectrum of one or more fragment ions, where the dopant is selected from one or more compounds having an ionization energy lower than the internal energy of a metastable species formed from the carrier gas that is suitable for one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a DART source with a carrier gas selected from the group consisting of helium, nitrogen and neon to generate ions of the sample, an argon DART source with an argon carrier gas and including a valve to add a dopant to the argon carrier gas to generate ions of the sample, a mass spectrometer for measuring a first mass spectrum of the ions generated from the sample, a mass spectrometer system for fragmenting intact ions generated of the sample ionized with the argon DART source and a mass spectrometer for measuring a second mass spectra of the one or more fragment ions, where the system includes a gas ion separator.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a first DART source to generate ions of the sample, a second DART source using helium carrier gas to generate ions of the sample, where a dopant is contacted with the helium carrier gas, a mass spectrometer for measuring mass spectra of the ions generated from the sample, a mass spectrometer system for fragmenting intact ions generated of the sample ionized with the second DART source and a mass spectrometer for measuring a mass spectrum of the one or more fragment ions, where the system further comprises a gas ion separator.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a source to generate predominantly protonated molecule ions of the sample, a source including a carrier gas and a dopant to generate predominantly molecular ions of the sample, a first mass filter for recording a first mass spectrum of the ions generated from the sample, a mass spectrometer system for fragmenting intact molecular ions and a second mass filter for recording a second mass spectrum of one or more fragment ions, where the carrier gas is argon, where the dopant is selected from one or more compounds having an ionization energy lower than the internal energy of a metastable argon species formed from the carrier gas, where the metastable argon species is capable of one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a source to generate predominantly protonated molecule ions of the sample, a source including a carrier gas and a dopant to generate predominantly molecular ions of the sample, a first mass filter for recording a first mass spectrum of the ions generated from the sample, a mass spectrometer system for fragmenting intact molecular ions and a second mass filter for recording a second mass spectrum of one or more fragment ions, where the dopant is selected from one or more compounds having an ionization energy lower than the internal energy of a metastable species formed from the carrier gas that is suitable for one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system for identifying a plurality of analytes present in a sample comprises a source to generate predominantly protonated molecule ions of the sample, a source including a carrier gas and a dopant to generate predominantly molecular ions of the sample, a first mass filter for recording a first mass spectrum of the ions generated from the sample, a mass spectrometer system for fragmenting intact molecular ions and a second mass filter for recording a second mass spectrum of one or more fragment ions, where the mass spectrometer system is an ion trap and the ion trap generates the first mass filter and the second mass filter.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a first plurality of ions of a sample, an argon DART source to generate a second plurality of ions of the sample, a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, and a valve to introduce an efficient dopant, where the efficient dopant is one or more compounds selected from the group consisting of anisole, toluene, acetone, chlorobenzene, bromobenzene, 2, 4-difluoroanisole, and 3-(trifluoromethyl)anisole.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a first plurality of ions of a sample, an argon DART source to generate a second plurality of ions of the sample, a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, and a valve to introduce an efficient dopant, where the efficient dopant is one or more compounds having an ionization energy lower than the internal energy of metastable argon that is suitable for one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a first plurality of ions of a sample, an argon DART source to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the one or more fragment ions are formed from ion activation, where the one or more fragment ions are formed from one or more methods selected from the group consisting of collisionally activated dissociation, collision induced dissociation, in source fragmentation, ion surface collisions, ion induced dissociation, photodissociation, ion neutral collisions, ion electron collisions, ion electron collisions, electron capture dissociation and function switching.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a first plurality of ions of a sample, an argon DART source to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the one or more fragment ions are formed from ion activation, where the one or more fragment ions are generated by function switching with an orifice-1 voltage set between a lower limit of approximately 10 V and an upper limit of approximately 250 V.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a first plurality of ions of a sample, an argon DART source to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the one or more fragment ions are formed from ion activation, where the one or more fragment ions are generated by function with an orifice-1 voltage set between a lower limit of approximately 30 V and an upper limit of approximately 200 V.

In an embodiment of the present invention, a method comprises directing a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the plurality of analytes, measuring a first mass spectrum of the first plurality of analytes, directing an argon DART source at the sample to form molecular ions of one or more of the plurality of analytes, measuring a second mass spectrum of the second plurality of analytes formed, and combining the first mass spectrum and the second mass spectrum to determine the plurality of analytes present in the sample, where the conventional DART source and argon DART source simultaneously generate ions of the sample.

In an embodiment of the present invention, a method comprises directing a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the plurality of analytes, measuring a first mass spectrum of the first plurality of analytes, directing an argon DART source at the sample to form molecular ions of one or more of the plurality of analytes, measuring a second mass spectrum of the second plurality of analytes formed, and combining the first mass spectrum and the second mass spectrum to determine the plurality of analytes present in the sample, where the argon DART source comprises a conventional DART source adapted to generate an argon carrier gas.

In an embodiment of the present invention, a method comprises directing a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the plurality of analytes, measuring a first mass spectrum of the first plurality of analytes, directing an argon DART source at the sample to form molecular ions of one or more of the plurality of analytes, measuring a second mass spectrum of the second plurality of analytes formed, combining the first mass spectrum and the second mass spectrum to determine the plurality of analytes present in the sample, and generating fragment ions of the molecular ions.

In an embodiment of the present invention, a method comprises directing a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the plurality of analytes, measuring a first mass spectrum of the first plurality of analytes, adding an efficient dopant, directing an argon DART source at the sample to form ions of the dopant to generate ions of one or more of the plurality of analytes, measuring a second mass spectrum of the second plurality of analytes formed, and combining the first mass spectrum and the second mass spectrum to determine the plurality of analytes present in the sample.

In an embodiment of the present invention, a method comprises directing a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the plurality of analytes, measuring a first mass spectrum of the first plurality of analytes, adding an efficient dopant, directing an argon DART source at the sample to form ions of the dopant to generate ions of one or more of the plurality of analytes, measuring a second mass spectrum of the second plurality of analytes formed, and combining the first mass spectrum and the second mass spectrum to determine the plurality of analytes present in the sample, where the efficient dopant is one or more compounds selected from the group consisting of anisole, toluene, acetone, chlorobenzene, bromobenzene, 2, 4-difluoroanisole, and 3-(trifluoromethyl)anisole.

In an embodiment of the present invention, a method comprises directing a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the plurality of analytes, measuring a first mass spectrum of the first plurality of analytes, adding an efficient dopant, directing an argon DART source at the sample to form ions of the dopant to generate ions of one or more of the plurality of analytes, measuring a second mass spectrum of the second plurality of analytes formed, and combining the first mass spectrum and the second mass spectrum to determine the plurality of analytes present in the sample, where the efficient dopant is one or more compounds having an ionization energy lower than the internal energy of metastable argon that is suitable for one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a method comprises directing a first carrier gas from a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the sample, measuring a first mass spectrum of the one or both positive ions and negative ions of the sample formed, introducing an efficient dopant, generating a plurality of dopant ions from the interaction of the efficient dopant with a second carrier gas of an argon DART source, directing the plurality of dopant ions at the sample to form intact ions of the sample, measuring a second mass spectrum of the ions of the sample formed, and combining the first mass spectrum and the second mass spectrum to determine one or more characteristic of the plurality of analytes present in the sample.

In an embodiment of the present invention, a method comprises directing a first carrier gas from a conventional DART source at a sample made up of a plurality of analytes to form one or both positive ions and negative ions of the sample, measuring a first mass spectrum of the one or both positive ions and negative ions of the sample formed, introducing an efficient dopant, generating a plurality of dopant ions from the interaction of the efficient dopant with a second carrier gas of an argon DART source, directing the plurality of dopant ions at the sample to form a plurality of intact ions of the sample, measuring a second mass spectrum of the ions of the sample formed, and combining the first mass spectrum and the second mass spectrum to determine one or more characteristic of the plurality of analytes present in the sample, further comprising generating fragment ions of the plurality of intact ions.

TABLE 1

Components in the PAH Native Standard Mixture ES-5438.

Each component was present at a concentration of 200 pg/mL

(200 ppm) in the standard solution.

Name
Composition
m/z

Anisole¹
C₇H₈O
108.05751

Naphthalene
C₁₀H₈
128.0626

Acenaphthylene
C₁₂H₈
152.0626

Acenaphthene
C₁₂H₁₀
154.07825

Fluorene
C₁₃H₁₀
166.07825

Phenanthrene
C₁₄H₁₀
178.07825

Anthracene, 9-methyl-²
C₁₅H₁₂
192.0939

Fluoranthene
C₁₆H₁₀
202.07825

Pyrene
C₁₆H₁₀
202.07825

Chrysene
C₁₈H₁₂
228.0939

Benz[a]anthracene
C₁₈H₁₂
228.0939

Benzo[a]pyrene
C₂₀H₁₂
252.0939

Benzo[b]fluoranthene
C₂₀H₁₂
252.0939

Benzo[k]fluoranthene
C₂₀H₁₂
252.0939

Perylene
C₂₀H₁₂
252.0939

Benzo[ghi]perylene
C₂₂H₁₂
276.0939

Indeno[1,2,3-cd]pyrene
C₂₂H₁₂
276.0939

Dibenz(a,h)anthracene³
C₂₂H₁₄
278.10955

¹Dopant;

²Internal standard;

³Unlisted component.

TABLE II

Major Ions Observed in FIG. 1B.

Origin
Formula
Assign
Calc.^a
m/z^b
δ^c
Intensity

Acetone
C3H6O
M + H
59.05050
59.04969
−0.81
100.000

Acetone
C3H6O
M + NH4
76.07440
76.07623
1.83
1.390

Acetone
C3H6O
2M + H
117.08990
117.09155
1.65
28.360

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE III

Major Ions Observed in FIG. 1C.

Origin
Formula
Assign
Calc.^a
m/z^b
δ^c
Intensity

Acetone
C3H6O
M + H
59.05200
59.04969
−2.31
2.

C5H9
C5H9

69.07160
69.07043
−1.17
5.030

Benzene
C6H6
M + H
79.05450
79.05478
0.28
1.230

Toluene
C7H8

92.06230
92.06260
0.30
100.000

Toluene
C7H8
M + H
93.07090
93.07043
−0.47
51.480

Anisole
C7H8O

108.05790
108.05751
−0.39
14.030

C8H12
C8H12

108.09460
108.09390
−0.70
1.000

Anisole
C7H8O
M + H
109.06420
109.06534
1.13
1.960

C8H12
C8H12
M + H
109.10270
109.10173
−0.97
16.670

C7H12O2
C7H12O2
M + H
129.09081
129.09156
0.75
5.460

TABLE IV

Major Ions Observed in FIG. 1D.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

Benzene
C6H6
78.04360
78.04695
3.35
1.340

Toluene
C7H8
92.05970
92.06260
2.90
1.390

Phenol
C6H6O
94.03970
94.04186
2.16
5.640

Anisole
C7H8O
108.05750
108.05751
0.01
100.000

C8H12
C8H12
108.09120
108.09390
2.70
1.910

C8H10O
C8H10O
122.07390
122.07317
−0.73
2.420

C9H12O
C9H12O
136.08980
136.08882
−0.98
1.240

C14H14O
C14H14O
198.10420
198.10447
0.27
1.530

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE V

Major Ions Observed in FIG. 1E.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

Benzene
C6H6
78.04250
78.04695
4.45
2.370

Toluene
C7H8
92.06180
92.06260
0.80
2.750

Phenol
C6H6O
94.04060
94.04186
1.26
61.840

Anisole
C7H8O
108.05750
108.05751
0.01
39.260

Chlorobenzene
C6H5Cl
112.00850
112.00798
−0.52
100.000

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE VI

Major Ions Observed in FIG. 2A.

Origin
Formula
Assign
Calc.^a
m/z^b
δ^c
Intensity

Anisole
C7H8O

108.05750
108.05751
0.01
100.000

Naphthalene
C10H8

128.06290
128.06260
−0.30
4.980

Acenaphthylene
C12H8

152.06300
152.06260
−0.40
4.930

Acenaphthene
C12H10

154.07800
154.07825
0.25
33.440

Fluorene
C13H10

166.07719
166.07825
1.06
8.100

Phenanthrene
C14H10

178.07651
178.07825
1.74
9.490

Anthracene(9-methyl)
C15H12

192.09270
192.09390
1.20
40.000

Phenanthrene
C14H10
M + NH4
196.11610
196.11262
−3.48
0.070

Fluoranthene
C16H10

202.07690
202.07825
1.35
71.390

Pyrene
C16H10

202.07690
202.07825
1.35
71.390

Benz[a]anthracene
C18H12

228.09219
228.09390
1.71
54.240

Chrysene
C18H12

228.09219
228.09390
1.71
54.240

Benzo[k]fluoranthene
C20H12

252.09419
252.09390
−0.29
94.970

Benzo[a]pyrene
C20H12

252.09419
252.09390
−0.29
94.970

Benzo[b]fluoranthene
C20H12

252.09419
252.09390
−0.29
94.970

Perylene
C20H12

252.09419
252.09390
−0.29
94.970

Indeno[1,2,3-cd]pyrene
C22H12

276.09451
276.09390
−0.61
16.000

Benzo[ghi]perylene
C22H12

276.09451
276.09390
−0.61
16.000

Dibenz(a,h)anthracene
C22H14

278.10941
278.10955
0.14
7.010

Dibenz(a,h)anthracene.
C22H14
M + NH4
296.14441
296.14392
−0.48
0.040

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE VII

Major Ions Observed in FIG. 2B.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

Anisole
C7H8O
108.05620
108.05751
1.31
100.000

Naphthalene
C10H8
128.06281
128.06260
−0.21
2.620

Acenaphthylene
C12H8
152.06149
152.06260
1.11
2.020

Acenaphthene
C12H10
154.07790
154.07825
0.35
5.600

Fluorene
C13H10
166.07710
166.07825
1.15
2.500

Phenanthrene
C14H10
178.07629
178.07825
1.96
2.160

Anthracene,
C15H12
192.09261
192.09390
1.29
3.270

9-methyl-

Fluoranthene
C16H10
202.07671
202.07825
1.54
3.480

Pyrene
C16H10
202.07671
202.07825
1.54
3.480

Benz[a]anthracene
C18H12
228.09210
228.09390
1.80
3.420

Chrysene
C18H12
228.09210
228.09390
1.80
3.420

Benzo-
C20H12
252.09390
252.09390
0.00
5.140

[k]fluoranthene

Benzo[a]pyrene
C20H12
252.09390
252.09390
0.00
5.140

Benzo-
C20H12
252.09390
252.09390
0.00
5.140

[b]fluoranthene

Perylene
C20H12
252.09390
252.09390
0.00
5.140

Indeno-
C22H12
276.09421
276.09390
−0.31
1.120

[1,2,3-cd]pyrene

Benzo-
C22H12
276.09421
276.09390
−0.31
1.120

[ghi]perylene

Dibenz-
C22H14
278.10889
278.10955
0.66
0.550

(a,h)anthracene

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE VIII

Major Ions Observed in FIG. 3A.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

C12 H12
C12H12
156.09390
156.09390
0.00
7.990

C13 H14
C13H14
170.10809
170.10955
1.46
19.580

C14 H14
C14H14
182.10831
182.10955
1.24
26.710

C14 H16
C14H16
184.12480
184.12520
0.40
24.740

C15 H16
C15H16
196.12270
196.12520
2.50
69.630

C16 H16
C16H16
208.12511
208.12520
0.09
20.880

C16 H18
C16H18
210.13960
210.14085
1.25
100.000

C16 H20
C16H20
212.15520
212.15650
1.30
12.130

C17 H18
C17H18
222.14020
222.14085
0.65
52.610

C17 H20
C17H20
224.15511
224.15650
1.39
70.280

C18 H14
C18H14
230.10899
230.10955
0.56
33.210

C18 H20
C18H20
236.15669
236.15650
−0.19
65.120

C18 H22
C18H22
238.17270
238.17215
−0.55
44.860

C19 H16
C19H16
244.12480
244.12520
0.40
28.810

C19 H22
C19H22
250.17340
250.17215
−1.25
50.510

C19 H24
C19H24
252.18739
252.18780
0.41
26.420

C20 H24
C20H24
264.18719
264.18780
0.61
30.450

C20 H26
C20H26
266.20380
266.20345
−0.35
15.000

C21 H26
C21H26
278.20432
278.20345
−0.87
17.100

^aCalculated mass;

bmeasured mass to charge;

^cdifference in millimass units.

TABLE IX

Major Ions Observed in FIG. 3B.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

C12 H12
C12H12
156.09390
156.09390
0.00
14.279

C13 H14
C13H14
170.10809
170.10955
1.46
34.790

C14 H14
C14H14
182.10831
182.10955
1.24
30.070

C14 H16
C14H16
184.12480
184.12520
0.40
40.361

C15 H16
C15H16
196.12469
196.12520
0.51
50.950

C16 H16
C16H16
208.12520
208.12520
0.00
10.050

C16 H18
C16H18
210.13960
210.14085
1.25
45.631

C16 H20
C16H20
212.15511
212.15650
1.39
17.411

C17 H18
C17H18
222.14020
222.14085
0.65
15.591

C17 H20
C17H20
224.15511
224.15650
1.39
28.979

C18 H14
C18H14
230.11121
230.10955
−1.66
6.340

C18 H20
C18H20
236.15680
236.15650
−0.30
13.950

C18 H22
C18H22
238.17050
238.17215
1.65
16.090

C19 H16
C19H16
244.12700
244.12520
−1.80
3.920

C19 H22
C19H22
250.17340
250.17215
−1.25
9.700

C19 H24
C19H24
252.18739
252.18780
0.41
8.460

C20 H24
C20H24
264.18951
264.18780
−1.71
5.680

C20 H26
C20H26
266.20370
266.20345
−0.25
4.771

C21 H26
C21H26
278.20432
278.20345
−0.87
3.410

Methyl
C19H36O2
296.26770
296.27153
3.83
20.670

oleate

C12 H12
C12H12 + H
157.10181
157.10173
−0.08
21.390

C13 H14
C13H14 + H
171.11591
171.11738
1.47
78.620

C14 H14
C14H14 + H
183.11520
183.11738
2.17
45.110

C14 H16
C14H16 + H
185.13310
185.13303
−0.08
76.920

C15 H16
C15H16 + H
197.13229
197.13303
0.73
70.060

C16 H16
C16H16 + H
209.13330
209.13303
−0.28
17.561

C16 H18
C16H18 + H
211.14830
211.14868
0.37
61.560

C16 H20
C16H20 + H
213.16440
213.16433
−0.07
21.799

C17 H18
C17H18 + H
223.14861
223.14868
0.07
21.730

C17 H20
C17H20 + H
225.16370
225.16433
0.63
36.611

C18 H14
C18H14 + H
231.11740
231.11738
−0.03
7.200

C18 H20
C18H20 + H
237.16479
237.16433
−0.47
18.580

C18 H22
C18H22 + H
239.18040
239.17998
−0.43
19.090

C19 H16
C19H16 + H
245.13120
245.13303
1.83
4.529

C19 H22
C19H22 + H
251.18060
251.17998
−0.63
12.830

C19 H24
C19H24 + H
253.19630
253.19563
−0.68
10.460

C20 H24
C20H24 + H
265.19571
265.19563
−0.08
7.610

C20 H26
C20H26 + H
267.21140
267.21128
−0.12
5.709

C21 H26
C21H26 + H
279.20990
279.21128
1.38
4.750

Methyl
C19H34O2 + H
295.26480
295.26371
−1.10
100.000

linoleate

Methyl
C19H36O2 + H
297.27979
297.27936
−0.43
59.260

oleate

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE X

Major Ions Observed in FIG. 4A.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

O2
O2
31.99030
31.98983
−0.47
15.630

Cl
Cl
34.97070
34.96885
−1.85
6.340

HCO2
HCO2
44.99630
44.99765
1.35
10.030

NO2
NO2
45.99170
45.99290
1.20
100.000

C2H3O2
C2H3O2
59.01450
59.01330
−1.20
11.330

CO3
CO3
59.98470
59.98474
0.04
68.590

HCO3
HCO3
60.99280
60.99257
−0.23
41.900

NO3
NO3
61.98840
61.98782
−0.58
18.770

C5H5O3
C5H5O3
113.01860
113.02387
5.27
16.90

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XI

Major Ions Observed in FIG. 4B.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

C7H7O
C7H7O
107.04990
107.04969
−0.21
4.990

C5H5O3
C5H5O3
113.02270
113.02387
1.17
6.270

C7H5O2
C7H5O2
121.02830
121.02895
0.65
18.060

C8H7O2
C8H7O2
135.04640
135.04460
−1.80
1.860

C7H7O4
C7H7O4—OH
138.03081
138.03169
0.88
1.380

C7H7O4
C7H7O4
155.03709
155.03443
−2.66
5.100

TNT
C7H5N3O6—NO
197.02110
197.01984
−1.26
14.360

TNT
C7H5N3O6—H
210.01601
210.01509
−0.92
5.200

C7H5N3O7
C7H5N3O7—NO
213.01500
213.01476
−0.24
1.970

TNT
C7H5N3O6—H
226.01140
226.01000
−1.39
100.000

TNT
C7H5N3O6
227.01781
227.01783
0.02
44.720

C7H5N3O7
C7H5N3O7
243.01379
243.01275
−1.04

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XII

Major Ions Observed in FIG. 4C.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

TNT
C7H5N3O6—NO
197.01700
197.01984
2.84
15.750

TNT
C7H5N3O6—OH
210.01379
210.01509
1.30
9.470

TNT
C7H5N3O6—H
226.00920
226.01000
0.80
18.860

TNT
C7H5N3O6
227.01781
227.01783
0.02
100.000

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XIII

Major Ions Observed in FIG. 5A.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

THC
C21H30O2
314.22409
314.22458
0.49
100.000

THC
C21H30O2 + H
315.22989
315.23241
2.52
64.920

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XIV

Major Ions Observed in FIG. 5B.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

CBD
C21H30O2
314.22409
314.22458
0.49
100.000

CBD
C21H30O2 + H
315.22989
315.23241
2.52
54.650

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XV

Major Ions Observed in FIG. 5C.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

THC
C12H17O2
193.12160
193.12285
1.25
14.760

THC
C14H17O2
217.12151
217.12285
1.34
5.579

THC
C14H21O2
221.15190
221.15416
2.26
6.200

THC
C15H19O2
231.13811
231.13850
0.39
30.170

THC
C15H21O2
233.15280
233.15416
1.36
7.011

THC
C16H19O2
243.13921
243.13850
−0.71
29.760

THC
C17H23O2
259.16910
259.16981
0.71
14.260

THC
C18H23O2
271.16949
271.16981
0.32
28.571

THC
C20H23O2
295.16989
295.16981
−0.08
10.560

THC
C21H29O1
297.22000
297.22184
1.84
5.410

THC
C20H27O2
299.20090
299.20111
0.21
95.741

THC
C21H29O2
313.21729
313.21676
−0.53
67.351

THC
C21H30O2
314.22409
314.22458
0.49
79.769

THC
C21H31O2
314.23239
315.23241
0.02
100.000

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XVI

Major Ions Observed in FIG. 5D.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

CBD
C12H17O2
193.12160
193.12285
1.25
100.000

CBD
C14H21O2
221.15190
221.15416
2.26
5.940

CBD
C15H19O2
231.13811
231.13850
0.39
76.730

CBD
C15H21O2
233.15280
233.15416
1.36
8.051

CBD
C17H23O2
259.16910
259.16981
0.71
12.400

CBD
C18H23O2
271.16949
271.16981
0.32
12.870

CBD
C20H23O2
295.16989
295.16981
−0.08
7.250

CBD
C20H27O2
299.20090
299.20111
0.21
15.080

CBD
C21H29O2
313.21481
313.21676
1.95
14.940

CBD
C21H30O2
314.22409
314.22458
0.49
15.510

CBD
C21H31O2
315.23239
315.23241
0.02
62.070

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XVII

Major Ions Observed in FIG. 5E.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

THC
C7H11
95.08500
95.08608
1.08
19.869

THC
C7H7O2
123.04560
123.04460
−1.00
31.971

THC
C12H11O2
187.07381
187.07590
2.09
16.879

THC
C12H17O2
193.12160
193.12285
1.25
63.681

THC
C13H13O2
201.08859
201.09155
2.96
24.588

THC
C14H17O2
217.12151
217.12285
1.34
59.749

THC
C15H19O2
231.13811
231.13850
0.39
100.000

THC
C15H21O2
233.15280
233.15416
1.36
11.711

THC
C16H19O2
243.13921
243.13850
−0.71
37.531

THC
C17H21O2
257.15341
257.15416
0.75
27.190

THC
C17H23O2
259.16919
259.16981
0.62
14.252

THC
C18H23O2
271.16949
271.16981
0.32
64.929

THC
C20H23O2
295.16989
295.16981
−0.08
23.401

THC
C20H27O2
299.20090
299.20111
0.21
70.611

THC
C21H29O2
313.21481
313.21676
1.95
21.920

THC
C21H30O2
314.22141
314.22458
3.17
6.849

THC
C21H31O2
315.22980
315.23241
2.61
7.101

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

TABLE XVIII

Major Ions Observed in FIG. 5F.

Origin
Formula
Calc.^a
m/z^b
δ^c
Intensity

CBD
C7H7O2
123.04560
123.04460
−1.00
55.020

CBD
C11H10O2
174.06590
174.06808
2.18
100.000

CBD
C12H11O2
187.07381
187.07590
2.09
10.439

CBD
C12H17O2
193.12160
193.12285
1.25
48.171

CBD
C13H13O2
201.08859
201.09155
2.96
7.301

CBD
C14H17O2
217.12360
217.12285
−0.75
12.661

CBD
C15H19O2
231.13811
231.13850
0.39
99.980

CBD
C16H19O2
243.13921
243.13850
−0.71
9.860

CBD
C17H21O2
257.15341
257.15416
0.75
9.689

CBD
C17H23O2
259.16919
259.16981
0.62
10.171

CBD
C18H23O2
271.17181
271.16981
−2.00
15.912

CBD
C20H23O2
295.16989
295.16981
−0.08
15.039

CBD
C20H27O2
299.20090
299.20111
0.21
10.059

^aCalculated mass;

^bmeasured mass to charge;

^cdifference in millimass units.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a carrier gas stream contacting a sample to generate a first plurality of ions of the sample, an dopant DART source to generate a dopant carrier gas contacting the sample; a dopant DART source to generate a second carrier gas stream contacting the sample, a valve for introducing a dopant into the second carrier gas stream contacting the sample to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the efficient dopant is one or more compounds selected from the group consisting of anisole, toluene, acetone, chlorobenzene, bromobenzene, 2, 4-difluoroanisole, and 3-(trifluoromethyl)anisole.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a carrier gas stream contacting a sample to generate a first plurality of ions of the sample, an dopant DART source to generate a dopant carrier gas contacting the sample, a dopant DART source to generate a second carrier gas stream contacting the sample, a valve for introducing a dopant into the second carrier gas stream contacting the sample to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the efficient dopant is selected from the group consisting of one or more compounds having an ionization energy lower than the internal energy of a metastable species formed by the dopant DART source.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a carrier gas stream contacting a sample to generate a first plurality of ions of the sample, an dopant DART source to generate a dopant carrier gas contacting the sample, a dopant DART source to generate a second carrier gas stream contacting the sample, a valve for introducing a dopant into the second carrier gas stream contacting the sample to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the efficient dopant is selected from the group consisting of one or more compounds having an ionization energy lower than the internal energy of a metastable species formed by the dopant DART source, where the metastable argon species is capable of one or both charge exchange and proton transfer to one or more of the plurality of analytes.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a carrier gas stream contacting a sample to generate a first plurality of ions of the sample, an dopant DART source to generate a dopant carrier gas contacting the sample, a dopant DART source to generate a second carrier gas stream contacting the sample, a valve for introducing a dopant into the second carrier gas stream contacting the sample to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the first plurality of ions include a negative ion, where the mass spectrometer system measures one or more fragment ions formed from the first plurality of ions.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a carrier gas stream contacting a sample to generate a first plurality of ions of the sample, an dopant DART source to generate a dopant carrier gas contacting the sample, a dopant DART source to generate a second carrier gas stream contacting the sample, a valve for introducing a dopant into the second carrier gas stream contacting the sample to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the mass spectrometer system measures one or more fragment ions formed from ion activation of the first plurality of ions, where the one or more fragment ions are formed from one or more methods selected from the group consisting of collisionally activated dissociation, collision induced dissociation, in source fragmentation, ion surface collisions, ion induced dissociation, photodissociation, ion neutral collisions, ion electron collisions, ion electron collisions, electron capture dissociation and function switching.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a carrier gas stream contacting a sample to generate a first plurality of ions of the sample, an dopant DART source to generate a dopant carrier gas contacting the sample, a dopant DART source to generate a second carrier gas stream contacting the sample, a valve for introducing a dopant into the second carrier gas stream contacting the sample to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the mass spectrometer system measures one or more fragment ions formed from ion activation of the first plurality of ions, where the one or more fragment ions are generated by function switching with an orifice-1 voltage set between a lower limit of approximately 10 V and an upper limit of approximately 250 V.

In an embodiment of the present invention, a system comprises a conventional DART source to generate a carrier gas stream contacting a sample to generate a first plurality of ions of the sample, an dopant DART source to generate a dopant carrier gas contacting the sample, a dopant DART source to generate a second carrier gas stream contacting the sample, a valve for introducing a dopant into the second carrier gas stream contacting the sample to generate a second plurality of ions of the sample, and a mass spectrometer system for measuring two or more of a mass spectrum of the first plurality of ions, one or more fragment ions formed from the first plurality of ions, a mass spectrum of the second plurality of ions and one or more fragment ions formed from the second plurality of ions, where the mass spectrometer system measures one or more fragment ions formed from ion activation of the first plurality of ions, where the one or more fragment ions are generated by function with an orifice-1 voltage set between a lower limit of approximately 30 V and an upper limit of approximately 200 V.

In an embodiment of the present invention, a method comprises directing a first carrier gas from a conventional DART source at a sample to form positive ions of the sample or negative ions of the sample, measuring positive ions of the sample or negative ions of the sample, introducing a dopant, generating a plurality of dopant ions from the interaction of the dopant with a second carrier gas formed from a dopant DART source, directing the plurality of dopant ions at the sample to form a plurality of intact ions of the sample, measuring a plurality of intact ions of the sample, and determining one or more chemical features of the sample based on the positive ions of the sample or negative ions of the sample and the plurality of intact ions of the sample.

While the systems, methods, and devices have been illustrated by the described examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and devices provided herein. Additional advantages and modifications will readily be apparent to those skilled in the art. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative system, method or device, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant's general inventive concept. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims. Furthermore, the preceding description is not meant to limit the scope of the invention. Rather, the scope of the invention is to be determined by the appended claims and their equivalents. In any multiply tuned circuit you have at least as many modes as you have inductors.

Number	Date	Country
2263578	Jul 1993	GB
2003185635	Jul 2003	JP
2003222574	Aug 2003	JP
2007525677	Jun 2007	JP
2009539114	Nov 2009	JP
WO03081205	Oct 2003	WO
WO2005094389	Oct 2005	WO
WO2008054393	May 2008	WO
WO2008082603	Jul 2008	WO
WO2015195599	Dec 2015	WO
WO2016145041	Sep 2016	WO

Dopant-assisted direct analysis in real time mass spectrometry

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

Field of Search

US

CPC

International Classifications

Abstract

Description

Claims

US Referenced Citations (210)

Foreign Referenced Citations (11)

Non-Patent Literature Citations (17)

Provisional Applications (1)

Number	Name	Date	Kind
3633027	Rhyage	Jan 1972	A
3957470	Dawes	May 1976	A
4016421	Hull	Apr 1977	A
4144451	Kambara	Mar 1979	A
4213326	Brodasky	Jul 1980	A
4542293	Fenn	Sep 1985	A
4546253	Tsuchiya	Oct 1985	A
4654052	Sharp	Mar 1987	A
4662914	Hansen	May 1987	A
4861988	Henion	Aug 1989	A
5012052	Hayes	Apr 1991	A
5055677	Amirav	Oct 1991	A
5137553	Dawes	Aug 1992	A
5192865	Zhu	Mar 1993	A
5306412	Whitehouse	Apr 1994	A
5352892	Mordehai	Oct 1994	A
5367163	Otsuka	Nov 1994	A
5381008	Tanner	Jan 1995	A
5412208	Covey	May 1995	A
5448062	Cooks	Sep 1995	A
5552599	Giessmann	Sep 1996	A
5559326	Goodley	Sep 1996	A
5614711	Li	Mar 1997	A
5624537	Turner	Apr 1997	A
5684300	Taylor	Nov 1997	A
5716825	Hancock	Feb 1998	A
5736741	Bertsch	Apr 1998	A
5788166	Valaskovic	Aug 1998	A
5859433	Franzen	Jan 1999	A
5868322	Loucks, Jr.	Feb 1999	A
5889404	Abdel	Mar 1999	A
5959297	Weinberg	Sep 1999	A
5997746	Valaskovic	Dec 1999	A
6107628	Smith	Aug 2000	A
6124675	Betrand	Sep 2000	A
6190559	Valaskovic	Feb 2001	B1
6225623	Turner	May 2001	B1
6297499	Fenn	Oct 2001	B1
6359275	Bertsch	Mar 2002	B1
6395183	Valaskovic	May 2002	B1
6562211	Kunnecke	May 2003	B1
6583408	Smith	Jun 2003	B2
6600155	Andrien, Jr.	Jul 2003	B1
6646256	Gourley	Nov 2003	B2
6649907	Ebeling	Nov 2003	B2
6670608	Taylor	Dec 2003	B1
6690006	Valaskovic	Feb 2004	B2
6713757	Tanner	Mar 2004	B2
6717139	Taniguchi	Apr 2004	B2
6723985	Schultz	Apr 2004	B2
6744041	Sheehan	Jun 2004	B2
6744046	Valaskovic	Jun 2004	B2
6753523	Whitehouse	Jun 2004	B1
6784424	Willoughby	Aug 2004	B1
6794642	Bateman	Sep 2004	B2
6803565	Smith	Oct 2004	B2
6806468	Laiko	Oct 2004	B2
6818889	Sheehan	Nov 2004	B1
6861647	Reilly	Mar 2005	B2
6875980	Bateman	Apr 2005	B2
6878930	Willoughby	Apr 2005	B1
6888132	Sheehan	May 2005	B1
6914243	Sheehan	Jul 2005	B2
6943347	Willoughby	Sep 2005	B1
6949739	Franzen	Sep 2005	B2
6949740	Sheehan	Sep 2005	B1
6949741	Cody	Sep 2005	B2
6956205	Park	Oct 2005	B2
6977372	Valaskovic	Dec 2005	B2
6979816	Tang	Dec 2005	B2
6987264	Whitehouse	Jan 2006	B1
6992299	Lee	Jan 2006	B2
7015466	Takats	Mar 2006	B2
7019289	Wang	Mar 2006	B2
7034292	Whitehouse	Apr 2006	B1
7041972	Bajic	May 2006	B2
7049584	Whitehouse	May 2006	B1
7053368	Thakur	May 2006	B2
7064317	McCluckey	Jun 2006	B2
7071464	Reinhold	Jul 2006	B2
7081618	Laprade	Jul 2006	B2
7081621	Willoughby	Jul 2006	B1
7095019	Sheehan	Aug 2006	B1
7098452	Schneider	Aug 2006	B2
7112785	Laramee	Sep 2006	B2
7138626	Karpetsky	Nov 2006	B1
7157698	Makarov	Jan 2007	B2
7161145	Oser	Jan 2007	B2
7196525	Sparkman	Mar 2007	B2
7247495	Amirav	Jul 2007	B2
7253406	Sheehan	Aug 2007	B1
7332345	Darrach	Feb 2008	B2
7423261	Truche	Sep 2008	B2
7429731	Karpetsky	Sep 2008	B1
7462826	Schneider	Dec 2008	B2
7544933	Cooks	Jun 2009	B2
7569812	Karpetsky	Aug 2009	B1
7582864	Verentchikov	Sep 2009	B2
7700913	Musselman	Apr 2010	B2
7705297	Musselman	Apr 2010	B2
7714281	Musselman	May 2010	B2
7777181	Musselman	Aug 2010	B2
7858926	Whitehouse	Dec 2010	B1
7893408	Hieftje	Feb 2011	B2
7915579	Chen	Mar 2011	B2
7923681	Collings	Apr 2011	B2
7928364	Musselman	Apr 2011	B2
7929138	Webb	Apr 2011	B1
7982183	Marakov	Jul 2011	B2
7982185	Whitehouse	Jul 2011	B2
8003935	Robinson	Aug 2011	B2
8026477	Musselman	Sep 2011	B2
8044346	Kostiainen	Oct 2011	B2
RE43078	Cody	Jan 2012	E
8101910	Loboda	Jan 2012	B2
8207497	Musselman	Jun 2012	B2
8217341	Musselman	Jul 2012	B2
8242459	Sun	Aug 2012	B2
8278619	Makarov	Oct 2012	B2
8304718	Ouyang	Nov 2012	B2
8308339	Karpetsky	Nov 2012	B2
8334507	Whitehouse	Dec 2012	B1
8362418	Xu	Jan 2013	B2
8410431	Ouyang	Apr 2013	B2
8421005	Musselman	Apr 2013	B2
8440965	Musselman	May 2013	B2
8481922	Musselman	Jul 2013	B2
8497474	Musselman	Jul 2013	B2
8519354	Charipar	Aug 2013	B2
8525109	Musselman	Sep 2013	B2
8563945	Musselman	Oct 2013	B2
RE44603	Cody	Nov 2013	E
8592756	Ouyang	Nov 2013	B2
8592758	Nilles	Nov 2013	B1
8604423	Enke	Dec 2013	B2
8648295	Enke	Feb 2014	B2
8664000	Yang	Mar 2014	B2
8686351	Ouyang	Apr 2014	B2
8704167	Cooks	Apr 2014	B2
8710437	Cooks	Apr 2014	B2
8729496	Musselman	May 2014	B2
8754365	Krechmer	Jun 2014	B2
8766178	Ouyang	Jul 2014	B2
8803085	Ouyang	Aug 2014	B2
8816275	Ouyang	Aug 2014	B2
8822949	Musselman	Sep 2014	B2
8853627	Ouyang	Oct 2014	B2
8859956	Ouyang	Oct 2014	B2
8859957	Ouyang	Oct 2014	B2
8859958	Ouyang	Oct 2014	B2
8859959	Ouyang	Oct 2014	B2
8890063	Ouyang	Nov 2014	B2
8895916	Musselman	Nov 2014	B2
8895918	Cooks	Nov 2014	B2
8927926	Shimada	Jan 2015	B2
8932875	Cooks	Jan 2015	B2
8933398	Ouyang	Jan 2015	B2
8937288	Cooks	Jan 2015	B1
8963079	Ouyang	Feb 2015	B2
8963101	Krechmer	Feb 2015	B2
9024254	Cooks	May 2015	B2
9064674	Ouyang	Jun 2015	B2
9105435	Musselman	Aug 2015	B1
9116154	Ouyang	Aug 2015	B2
9159540	Ouyang	Oct 2015	B2
9165752	Cooks	Oct 2015	B2
9224587	Musselman	Dec 2015	B2
9230792	Cooks	Feb 2016	B2
9337007	Musselman	May 2016	B2
9484195	Ouyang	Nov 2016	B2
9500630	Cooks	Nov 2016	B2
9514923	Krechmer	Dec 2016	B2
9548192	Cooks	Jan 2017	B2
9558926	Musselman	Jan 2017	B2
20020121596	Laiko	Sep 2002	A1
20020121598	Park	Sep 2002	A1
20020162967	Atkinson	Nov 2002	A1
20020185593	Doring	Dec 2002	A1
20020185595	Smith	Dec 2002	A1
20020185606	Smith	Dec 2002	A1
20030052268	Doroshenko	Mar 2003	A1
20040094706	Covey	May 2004	A1
20040129876	Franzen	Jul 2004	A1
20040159784	Doroshenko	Aug 2004	A1
20050230635	Takats	Oct 2005	A1
20050236374	Blankenship	Oct 2005	A1
20060266941	Vestal	Nov 2006	A1
20070114389	Karpetsky	May 2007	A1
20070228271	Truche	Oct 2007	A1
20080156985	Venter	Jul 2008	A1
20080202915	Hieftje	Aug 2008	A1
20080217254	Anderson	Sep 2008	A1
20100078550	Wiseman	Apr 2010	A1
20110215798	Beer	Sep 2011	A1
20120006983	Cody	Jan 2012	A1
20120138783	Peng	Jun 2012	A1
20120145890	Goodlett et al.	Jun 2012	A1
20120208004	Wolcott	Aug 2012	A1
20120223226	Rafferty	Sep 2012	A1
20120312980	Whitehouse	Dec 2012	A1
20120322683	Liu	Dec 2012	A1
20130020482	Enke	Jan 2013	A1
20130037710	Wu	Feb 2013	A1
20130082172	Syage	Apr 2013	A1
20130092832	Enke	Apr 2013	A1
20130273552	Ohashi	Oct 2013	A1
20130284915	Shimada	Oct 2013	A1
20140024822	Connolly	Jan 2014	A1
20150233866	Verenchikov	Aug 2015	A1
20160314956	Cooks	Oct 2016	A1

Entry
The AccuTOF-DART Mass Spectrometer, Jan. 1, 2006, pp. 1-6; www.jeolusa.com/SERVICESUPPORT/ApplicationsResources/AnalyticalInstruments/Documents/Downloads/tabid/337/DMXModule/693/CommandCore—Download/Default.aspx?EntryId=171.
Cody, R.B. et al., “Versatile New Ion Source for the Analysis of Materials in Open Air under Ambient Conditions” Anal. Chem., 2005, 77, 2297-2302.
Cooks, R.G. et al., “Ambient Mass Spectrometry”, Science, 2006, 311, 1566-1570.
Dalton, C.N. et al., “Electrospray-Atmospheric Sampling Glow Discharge Ionization Source for the Direct Analysis of Liquid Samples”, Analytical Chemistry, Apr. 1, 2003, vol. 75, No. 7, pp. 1620-1627.
Garimella, S. et al., “Gas-flow assisted ion transfer for mass spectrometry”, J. Mass Spectrom. 2012, 17, 201-207.
Guzowski, J.P. Jr. et al., “Development of a Direct Current Gas Sampling Glow Discharge Ionization Source for the Time-of-Flight Mass Spectrometer”, J. Anal. At. Spectrom., 14, 1999, pp. 1121-1127.
Haddad, R., et al., “Easy Ambient Sonic-Spray Ionization Mass Spectrometry Combined with Thin-Layer Chromatography,” Analytical Chemistry, vol. 80, No. 8, Apr. 15, 2008, pp. 2744-2750.
Harris, Glenn A. et al., Ambient Sampling/Ionization Mass Spectrometry: Applications and Current Trends, Apr. 15, 2011, Anal. Chem. 2011, 83, pp. 4508-4538.
Harris, Glenn A. et al., Simulations and Experimental Investigation of Atmospheric Transport in an Ambient Metastable-Induced Chemical Ionization Source, Anal. Chem. 2009, 81, pp. 322-329.
Hill, C.A. et al., “A pulsed corona discharge switchable high resolution ion mobility spectrometer-mass spectrometer”, Analyst, 2003, 128, pp. 55-60.
Hiraoka, K. et al., “Atmospheric-Pressure Penning Ionization Mass Spectrometry”, Rapid Commun. Mass Spectrom., 18, 2004, pp. 2323-2330.
McLuckey, S.A. et al., “Atmospheric Sampling Glow Discharge Ionization Source for the Determination of Trace Organic Compounds in Ambient Air”, Anal. Chem., 60, 1988, pp. 2220-2227.
Otsuka, K. et al., “An Interface for Liquid Chromatograph/Liquid Ionization Mass Spectrometer”, Analytical Sciences, Oct. 1988, vol. 4, pp. 467-472.
Takáts et al., “Mass Spectrometry Sampling Under Ambient Conditions with Desorption Electrospray Ionization,” Science, vol. 306, No. 5695, Oct. 15, 2004, pp. 471-473.
Tembreull, R., et al., “Pulsed Laser Desorption with Resonant Two-Photon Ionization Detection in Supersonic Beam Mass Spectrometry,” Anal. Chem., vol. 58, 1986, pp. 1299-1303, p. 1299.
Yang, H. et al., Argon Direct Analysis in Real Time Mass Spectrometry in Conjunction with Makeup Solvents, A method for Analysis of Labile Compounds, Anal Chem, vol. 85, 2013, pp. 1305-1309.
Zhao, J. et al., Liquid Sample Injection Using an Atmospheric Pressure Direct Current Glow Discharge Ionization Source, Analytical Chemistry, Jul. 1, 1992, vol. 64, No. 13, pp. 1426-1433.