Patent Application
20080087817
Reference is now made to the following drawings. Note that the components in the drawings are not necessarily to scale.
Embodiments of the present disclosure will employ, unless otherwise indicated, techniques of chemistry, biochemistry, molecular biology, spectroscopy, liquid chromatography, and the like, that are within the skill of the art. Such techniques are explained fully in the literature.
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to perform the methods and use the compositions disclosed and claimed herein. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C., and pressure is at or near atmospheric. Standard temperature and pressure are defined as 20° C. and 1 atmosphere.
Before the embodiments of the present disclosure are described in detail, it is to be understood that, unless otherwise indicated, the present disclosure is not limited to particular materials, reagents, reaction materials, manufacturing processes, or the like, as such can vary. It is also to be understood that the terminology used herein is for purposes of describing particular embodiments only, and is not intended to be limiting. It is also possible in the present disclosure that steps can be executed in different sequence where this is logically possible.
It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a support” includes a plurality of supports. In this specification and in the claims that follow, reference will be made to a number of terms that shall be defined to have the following meanings unless a contrary intention is apparent.
Embodiments of the present disclosure include mass spectrometry systems and methods of use thereof. The mass spectrometry system includes an integrated ionization source. The integrated ionization source includes an inductively coupled plasma (ICP) ionization source and an electrospray ionization (ESI) source. The integrated ionization source is interfaced with a single mass analyzer.
The mass spectrometry system can be used to analyze various types of samples such as, but not limited to, biological samples, serum samples, protein samples, and the like. In particular, mass spectrometry system can be used to analyze metalloprotein samples. The integrated ionization source is configured to operate as an ICP ionization source when operated in a “RF on” mode, and is configured to operate as an ESI source when operated in a “RF off” mode. The “RF on” mode can be used to perform elemental analysis, while the “RF off” mode can be used to perform molecular analysis. At least one advantage of the mass spectrometry system is that a single integrated ionization source can be used to perform molecular and elemental analysis. A further benefit is that only a single mass analyzer is needed to perform the molecular and elemental analysis.
In contrast, current technologies for metallomic and metalloproteomics studies require splitting up a sample and analyzing the two portions separately with two mass spectrometry systems (an ESI-MS and an ICP-MS). The configuration and set-up needed to analyze the sample is complicated, time consuming, and costly. Embodiments of the present disclosure can analyze samples without splitting the sample and using a much less expensive and complicated system (e.g., a single mass analyzer). By eliminating the complexity of the previous systems, embodiments of the present disclosure should find application in many studies such as metallomic and metalloproteomics studies. The presence of a covalently bound metal ion or other heteroatom makes ICP-MS very attractive for elemental analysis and quantitative work, while ESI-MS retains its identification power at the molecular level.
ICP-MS is a mass dependent detector and interfacing it with capillary HPLC would be beneficial because of both increased transport of the analyte to the plasma and increased ionization efficiency in the plasma because of the decreased flow rate that is being used in capillary HPLC. The reduced flow rate also makes possible use of acetonitrile and other organic solvents as mobile phases in HPLC, which are quite compatible with embodiments of the present disclosure.
The separation system 14 can include, but is not limited to, a liquid chromatograph system (e.g., HPLC), an electrophoresis system (e.g., CE), ion chromatograph (IC), and a gas chromatograph (GC). The liquid chromatograph system can include, but is not limited to, a column (e.g., Zorbax SB C3, 0.3 mm i.d.×150 mm length×3.5 μm particles).
The separation system 14 is interfaced with a capillary tube (additional details in
In the “RF off” mode, a potential difference (e.g., about 2000 to 4000 volts) is generated between a capillary tube (that is electrically conductive) disposed in the integrated ionization source 16 and the mass spectrometer interface 18. The sample passes through the capillary tube. The sample is electrosprayed from the capillary tube and compounds in the sample are ionized. The ions can flow through the mass spectrometer interface 18, into the mass analyzer 22, and subsequently mass analyzed.
The mass spectrometer interface 18 separates the atmospheric pressure region present in the integrated ionization source 16 from the low-pressure (e.g., 10−5 torr) region of the mass analyzer 22. The mass spectrometer interface 18 can include, but is not limited to, a sampling plate, a skimmer plate, electrostatic ion lenses, and a radiofrequency multipole ion guide. In an embodiment, the sampling plate includes a small diameter (e.g., 0.5 to 2 mm i.d.) orifice that separates the mass spectrometer interface 18 from the mass analyzer 22. A portion of the ions generated can pass through the orifice. A voltage can be applied to the skimmer plate to attract the ions to the orifice. In addition, the mass spectrometer interface 18 includes, but is not limited to, one or more vacuum pumps and other vacuum equipment. In an embodiment, an electrostatic lens system can be used to guide and/or focus the ions. Vacuum systems and ion focusing systems are known to those skilled in the art.
The mass analyzer 22 can include, but is not limited to, a time-of-flight (TOF) mass analyzer system, a quadrupole (Q) mass analyzer system, a Q-TOF mass analyzer system, an ion trap mass analyzer system (IT-MS), an ion cyclotron resonance mass analyzer system (e.g., FTICR-MS), and an orbitrap system. An ion detector can be disposed adjacent the mass analyzer to detect the ions. The ion detector can include, for example, a faraday cup detector (with or without phase sensitive detection), a microchannel plate multiplier detector, an electron multiplier detector, or a combination thereof. The mass analyzer 22 can include appropriate electronic systems, vacuum systems, and the like.
In an embodiment, the capillary tube 32 is concentrically located within the inner tube 34. The inner tube 34 is concentrically located within the middle tube 36. The middle tube 36 is concentrically located within the outer tube 38. In another embodiment, additional tubes can be used to flow one or more gases.
A sample can be flowed through the capillary tube 32. The sample can be flowed at a rate of about 20 nL/min to 100 μL/min. Gas “A” can be flowed through inner tube 34. Gas “B” can be flowed through middle tube 36. Gas “C” can be flowed through outer tube 38.
Gas “A” can be referred to as the make-up gas and/or nebulization gas. Gas “A” can include, but is not limited to, argon, helium, nitrogen and combinations thereof. Gas “A” can be flowed at a rate of about 0.3 to 3 L/min.
Gas “B” can be referred to as the auxiliary gas, which are known in the art. Gas “B” can be flowed at a rate of about 0.1 to 2 L/min and typically about 1 L/min.
Gas “C” can be referred to as the cooling gas. Gas “C” can include, but is not limited to, Ar and the like. Gas “C” can be flowed at a rate of about 10 to 20 or about 12 to 15 L/min.
Each of the inner tube 34, the middle tube 36, and the outer tube 38 can be independently made of materials such as, but not limited to, quartz, glass, ceramic, and combinations thereof.
The inner tube 34 can have a length of about 50 to 200 mm. The inner tube 34 can have a diameter of about 3 to 6 mm. The middle tube 36 can have a length of about 50 to 200 mm. The middle tube 36 can have a diameter of about 5 to 8 mm. The outer tube 38 can have a length of about 50 to 200 mm. The outer tube 38 can have a diameter of about 8 to 20 mm.
The capillary tube 32 can be made of a conductive material or a non-conductive material. The conductive material can include materials such as, but not limited to, stainless steel, metalized polymers, metalized glass, or quartz. The non-conductive materials can include materials such as, but not limited to, quartz, glass, or ceramic. The length of the capillary tube 32 can be from about 50 to 200 mm. However, the length depends, in part, upon the length of the inner tube 34, the middle tube 36, and the outer tube 38. The diameter of the capillary tube 32 can be about 1 to 2 mm. A voltage potential can be applied to the capillary tube 32 (e.g., a conductive capillary tube) or through the sample flowing through the capillary tube 32 in the “RF off” mode via a voltage source 52. In an embodiment, the capillary tube 32 can be heated. )
A RF coil 42 is disposed around a portion of the second end of the outer tube 38. RF power can be applied to the RF coil 42 to generate a plasma within a portion of the integrated ionization source 16 under appropriate ICP conditions in the “RF on” mode.
As described briefly above, a sample from the separation system flows into the capillary tube of the integrated ionization source. The sample traverses the length of the capillary tube. The integrated ionization source can be operated in the “RF on” mode for elemental analysis or in the “RF off” mode for molecular analysis.
In the “RF on” mode, a radiofrequency current is sent through the RF coil such that a plasma is generated in a portion of the integrated ionization source adjacent the coil and the exit of the capillary tube. The sample exits the capillary tube and is entrained into a gas and flowed into the plasma. The plasma desolvates, atomizes, and/or ionizes the sample to form sample ions. The mass spectrometer interface is disposed adjacent the integrated ionization source. The ions are attracted to the mass spectrometer interface and pass through an orifice in the mass spectrometer interface. The ions enter the mass analyzer and are detected.
In the “RF off” mode, the radiofrequency power is turned off and a voltage difference is generated between the capillary tube disposed in the integrated ionization source and the mass spectrometer interface. The sample is electrosprayed from the capillary tube and compounds in the sample are ionized. The ions are attracted to the mass spectrometer interface and pass through an orifice in the mass spectrometer interface. The ions enter the mass analyzer and are detected.
It should be noted that ratios, lengths, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited.
Many variations and modifications may be made to the above-described embodiments. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.
All patents, patent applications, and publications mentioned herein are hereby incorporated by reference in their entireties.
