Patent Application
20140260540
The present invention relates generally to gas chromatography (GC), and more particularly sample inlets utilized with GC instruments.
Gas chromatography (GC) entails the analytical separation of a vaporized or gas-phase sample that is injected into a chromatographic column. The column is typically housed in a thermally controlled oven. A chemically inert carrier gas, such as helium, nitrogen, argon, or hydrogen, is utilized as the mobile phase for elution of the analyte sample in the column. The sample and carrier gas are separately introduced into a GC inlet coupled to the column head. In the GC inlet, the sample is injected into the carrier gas stream and the resulting sample-carrier gas mixture flows through the column. The typical GC inlet is configured for vaporizing an initially liquid-phase sample, and may provide a liner configured for performing pre-column separation as well. During column flow the sample encounters a stationary phase (a coating or packing), which causes different components of the sample to separate according to different affinities with the stationary phase. The separated components elute from the column exit and are measured by a detector, producing data from which a chromatogram or spectrum identifying the components may be constructed.
The typical GC inlet is configured for vaporizing an initially liquid-phase sample, and may provide a liner configured for performing pre-column separation as well. The performance of the GC inlet is recognized as playing a key role in the overall performance of a GC-based instrument, including hybrid instruments such as a gas chromatograph-mass spectrometer (GC-MS). While GC inlets have evolved over the years, their designs have largely remained optimized around a temperature controlled chamber with electronically controlled flows and which contains a liner of sufficient volume and chemical inertness for expansion of a small liquid injection. The circumstances surrounding the transfer of vapors from this sample volume in the liner to a GC column govern issues such as, for example, resolution, detection limits, sample discrimination, and sample carryover.
There has long been interest in the selective discrimination between wanted and unwanted components in a GC sample. The typical ideal target would be transferring 100% of the analytes of interest to the GC column and transferring 0% of unwanted components such as heavy, poorly volatile components (often referred to as “background” or “matrix”) and likely the sample's solvent as well. Heavy, poorly volatile components can foul the GC column and downstream components, as well as the liner itself. Solvents can be a burden to the stationary phase of the GC column, overload or mask the separation of analytes, and also damage detection components. The transfer of matrix can be especially problematic for expensive components such as low thermal mass (LTM) GC columns, which are only marginally amenable to column “cut-back” to remove a contaminated column end at the inlet. Moreover, mass spectrometers can slowly accumulate heavy contaminants following transfer of matrix to the GC column and temperature programming of the column.
Known GC inlets are capable of temperature programming, but the level of discrimination provided thereby is too crude to be useful as it does not provide a sharp cut-off between analytes of interest and slightly less volatile non-analyte materials. This problem has been addressed to some extent by employing back-flushable pre-columns. However, pre-columns complicate chromatographs and are located in the GC oven, thus adding to the footprint of a GC instrument. Moreover, when employing an LTM GC column, typically a guard column is provided between the low thermal mass GC column and the GC inlet to protect the LTM GC column from contaminants. The guard column is often contained in a small isothermal oven, which increases the footprint of the GC instrument. Hence, the requirement of a pre-column or guard column does not promote the development of smaller, lighter, mobile, and lower power GC instruments.
Efforts have been made to increase discrimination at the GC inlet, including programmed temperature vaporization (PTV), the use of cryogens to extend the temperature range in the GC inlet, and the of sorbent materials in the GC inlet. An example of PTV is disclosed in U.S. Pat. Nos. 5,827,353 and 5,944,877, the entire contents of which are incorporated herein by reference. These patents, which have been commercialized by Apex Technologies, Inc., Independence, Ky., disclose a split/splitless GC inlet with temperature controlling capability, and which includes a liner having no stationary phase, or alternatively having a stationary phase in the form of a packing of beads or a coating on the inside surface of the liner. Evaluation of this GC inlet has revealed that it is capable of only a slight amount of analyte separation.
In view of the foregoing, there is an ongoing need for GC inlets and methods for reducing or eliminating matrix transfer while optimally transferring analytes of interest to a GC column.
To address the foregoing problems, in whole or in part, and/or other problems that may have been observed by persons skilled in the art, the present disclosure provides methods, processes, systems, apparatus, instruments, and/or devices, as described by way of example in implementations set forth below.
According to one embodiment, a gas chromatograph (GC) inlet device includes: an inlet chamber; a sample inlet communicating with the inlet chamber; a carrier gas inlet communicating with the inlet chamber; a liner chamber comprising a first end communicating with the inlet chamber and an axially opposing second end; a plurality of parallel capillaries disposed in the liner chamber; an outlet chamber communicating with the second end; and an outlet port communicating with the outlet chamber for coupling with a GC column.
According to another embodiment, a gas chromatograph (GC) includes: the GC inlet device; and a GC column communicating with the outlet port.
According to another embodiment, a gas chromatograph (GC) inlet assembly includes a vaporization device and a GC inlet device. The vaporization device may include: a vaporization chamber; a carrier gas inlet communicating with the vaporization chamber; a heater configured for heating the vaporization chamber; and a first outlet port communicating with the vaporization chamber. The GC inlet device may include: an inlet chamber communicating with the first outlet port; a sample inlet communicating with the inlet chamber; a liner chamber comprising a first end communicating with the inlet chamber and an axially opposing second end; a plurality of parallel capillaries disposed in the liner chamber; an outlet chamber communicating with the second end; and a second outlet port communicating with the outlet chamber for coupling with a GC column.
According to another embodiment, a method for introducing a sample to a gas chromatograph (GC) chamber includes: flowing a sample and a carrier gas through a liner chamber; separating components of the sample by flowing the sample through a plurality of parallel capillaries disposed in the liner chamber; and flowing the sample from the liner chamber to the GC column.
According to another embodiment, a gas chromatograph (GC) inlet device is configured for performing any of the methods disclosed herein.
Other devices, apparatus, systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.
The invention can be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.
In the context of the present disclosure, the term “analyte” refers generally to any sample molecule of interest to a researcher or user of a gas chromatograph (GC)—that is, a molecule on which an analysis is desired such as, for example, a chromatographic or chromatographic/mass spectral analysis. The term “sample” or “sample matrix” refers to any substance known or suspected of containing analytes. The sample may include a combination of analytes and non-analytes. The term “non-analytes” or “non-analytical components” in this context refers to components of the sample for which analysis is not of interest because such components do not have analytical value and/or impair (e.g., interfere with) the analysis of the desired analytes. Non-analytes may generally be any molecules not of interest such as contaminants or impurities. Examples of non-analytes may include, but are not limited to, water, oils, solvents or other media in which the desired analytes may be found, as well as stationary phase material that has bled from a chromatographic column.
As used herein, for convenience the term “gas” encompasses vapors, and gases in which vapors, droplets or particles may be entrained.
The GC column 108 may have any configuration now known or later developed. The GC column 108 includes an appropriate stationary phase. As illustrated, a portion of the GC column 108 may be coiled to accommodate a desired length while minimizing the size of the housing 108.
The detector 112 may any detector suitable for detecting peaks eluting from the GC column 108. Examples of detectors include, but are not limited to, flame ionization detectors (FID), thermal conductivity detectors (TCD), electron capture detectors (ECD), flame thermionic detectors (FTD), flame photometric detectors (FPD), etc. Generally, a wide variety of detectors may be utilized, and the illustrated detector 112 may represent a combination of two or more different types of detectors. In some embodiments, the detector 112 is, or is part of, an analytical instrument such as, for example, a mass spectrometer (MS), an ion mobility spectrometer (IMS), etc. Thus, in some embodiments, the GC system 100 may be a hyphenated system such as a GC-MS or GC-IMS system. The detector 112 may also be schematically representative of a data acquisition system, display/readout device, and other components associated with generating chromatograms and spectra as appreciated by persons skilled in the art.
The heating device 132 may have any configuration suitable for maintaining the GC column 108 at a desired temperature setting or for varying the temperature of the GC column 108 according to a desired (predetermined) temperature profile, such as for balancing parameters such as elution time and measurement resolution. In some embodiments, the housing 116 is or includes a temperature-programmable GC oven, and the heating device 132 is configured for heating the interior of the oven through which the GC column 108 extends. In other embodiments, the heating device 132 is configured for heating the GC column 108 directly. For example, the heating device 132 may include a resistive heating element mounted in thermal contact with the GC column 108.
The sample introduction device 120 may be any device configured for injecting a sample into the GC inlet device 104. Sample injection may be carried out on an automated, semi-automated or manual basis. The sample introduction device 120 may, for example, include a manually operated syringe or a syringe that is part of an automated sampling apparatus (or “autosampler”). The sample source 124 may be located upstream of the sample introduction device 120, or may be one or more sample containers (as illustrated) provided at the sample introduction device 120. In the latter case, the sample containers may be loaded on a carousel or other device that selects a desired sample for injection into the GC column 108.
The carrier gas source 128 supplies a carrier gas to the GC inlet device 104 via a carrier gas line 136 at a regulated flow rate and/or pressure. The carrier gas may be any gas suitable for serving as an inert mobile phase that facilitates transport of the sample through the GC column 108 as appreciated by persons skilled in the art. Examples of carrier gases include, but are not limited to, helium, nitrogen, argon, and hydrogen. The GC inlet device 104 introduces the sample flow into the carrier gas flow, and processes the mixture in a manner described below. The GC inlet device 104 may be located in the housing (oven) 116, in which case it may be enclosed in a thermally insulating cup.
The inlet chamber 250 includes a sample inlet 268 configured for communicating with a sample introduction device. In some embodiments, the sample inlet 268 includes a septum or other closure member for receiving a needle 270 of the sample introduction device. The inlet chamber 250 also includes a (first) carrier gas inlet 272 configured for communicating with a (first) carrier gas line. The inlet chamber 250 may also include a (first) purge outlet 274 configured for purging gas to a (first) purge vent 276.
The outlet chamber 260 includes an outlet port 278 configured for communicating with a GC column. The outlet chamber 260 may also include a (second) carrier gas inlet 280 configured for communicating with a (second) carrier gas line. The outlet chamber 260 may also include a (second) purge outlet 282 configured for purging gas to a (second) purge vent 284. In some embodiments, the outlet chamber 260 is extended around all or a portion of the axial length of the liner chamber 254. That is, the outlet chamber 260 may include an annular section 286 coaxially surrounding the liner chamber 254. In some embodiments, the inlet chamber 250 and outlet chamber 260 are formed from a cylindrical structure and separated by a sealing element, such as an o-ring 288 surrounding the liner chamber 254, as illustrated.
The temperature control device 264 may include a heating device 206 which, by example, is shown is coaxially surrounding the inlet chamber 250, liner chamber 254, and outlet chamber 260. In some embodiments, the heating device 206 is configured for heating the inlet chamber 250 to vaporize sample material upstream of the liner chamber 254. In other embodiments, the heating device 206 is configured for also heating the liner chamber 254 and MCL 256. The heating device 206 may be configured for providing a temperature gradient along the axial length of the GC inlet device 204. In some embodiments, the heating device 206 may include one or more heating zones 210. Distinct heating zones 210 may facilitate establishing a temperature gradient, or for heating one or more selected regions of the liner chamber 254. In some embodiments, one or more of the heating zones 210 may be independently controlled to maintain different temperature settings along the length of the GC inlet device 204. For example, the uppermost heating zone 210 in closest thermal contact with the inlet chamber 254 may provide the highest temperature for vaporizing the sample, while one or more lower heating zones 210 may maintain the MCL 256 at lower temperatures designed to optimize chromatography with the most volatile early eluters. Each heating zone 210 may schematically represent a heating component such as, for example, an electrically resistive heating element or a chamber through which a heat transfer medium (gas or liquid) is routed.
In some embodiments, the inlet chamber 250 and corresponding heating zone 210 may be part of a separate, upstream device (a vaporizing device, or vaporizer), in which case vaporized sample material and carrier gas may flow from an outlet of the upstream device to an inlet leading to the liner chamber 254. Providing an upstream vaporizing device may facilitate optimizing the vaporization and pre-GC column separation processes.
In some embodiments, the temperature control device 264 may also include a cooling device 222. The cooling device 222 may include a cooling jacket 226 for routing a heat transfer medium (gas or liquid) from an inlet 230 to an outlet 234 which, it will be understood, have been arbitrarily located in
The MCL 256 includes a parallel array or bundle of small-bore tubes, or capillaries 238, as further shown in
Testing of examples of a GC inlet device that included the MCL 256 with open interstices has demonstrated significantly improved chromatographic separation performance over GC inlet devices equipped with conventional liners such as liners containing packed beads. However,
Although the MCL 256 with open interstices offers superior separation performance, the bypass flow through the interstices may affect performance in some applications. The sizes of the interstices may be minimized by bundling the capillaries 238 in a closely packed arrangement such as a hexagonal array (honeycomb), as illustrated in
In the illustrated embodiment, the GC inlet device 204 includes a carrier gas line, which in some embodiments is split into a first carrier gas line 472 and a second carrier gas line 480. The carrier gas lines 472 and 480 terminate at or are coupled to the carrier gas inlets 272 and 280 described above in conjunction with
In the illustrated embodiment, the GC inlet device 204 further includes respective mass flow controllers (MFC) 490 and 492 operatively located on the carrier gas lines 472 and 480, a forward pressure controller (FPC) 494 operatively located on the first purge line 474, and a back pressure controller (BPC) 496 operatively located on the second purge line 482. A fit 498 or other flow restricting component may also be located on the first purge line 474. Other components that may be provided may include valves for regulating flow rate, switchable valves for selecting flow paths, flow meters, pressure transducers, tee-connections or unions for splitting or merging flow paths, etc., all as understood by persons skilled in the art. It is also understood that flow and pressure controllers may be controlled by an appropriately configured system controller (electronic hardware, firmware, software, etc.) that may be provided with the GC system in which the GC inlet device 204 operates.
As noted earlier in this disclosure, it is desirable to achieve a sufficient degree of separation in a GC inlet device to allow the inlet to selectively pass analytes of interest to the GC column while minimizing loss of analytes (and ideally without any loss of analyte). This may be addressed by splitting away unwanted solvent, or preventing late eluting components that are less volatile than the analytes from being transferred to the GC column. This latter ability to have the inlet selectively discriminate against later eluting, low volatility compounds is of special interest for protecting the GC column from accumulating contamination from poorly volatile material present in the sample matrix. This is also of particular interest when employing comparatively expensive column types such as low thermal mass column assemblies in conjunction with samples known to have complex matrices that are rich in such contaminating materials.
The GC inlet device 204 with the MCL 256 as disclosed herein is operable to achieve a high degree of separation so that eluting compounds may be selectively split or cut from the sequence of compounds eluting from the GC inlet device 204 to the GC column. The GC inlet device 204 is operable to allow analytes of interest to pass directly to the GC column without discrimination, and to reject components not of interest. For example, the GC inlet device 204 may be operated to reject early eluting solvent (such as be operating in a split mode as described below), thereby sparing the GC column and detector from the large quantity of solvent typically present as compared to the quantity of analytes. Rejection of early eluters may be followed by passing the analytes of interest to the GC column (such as by switching to a splitless mode as described below), during which time analytes may be subjected to pre-column separation activity in the MCL 256. After transferring the last analytes of interest, the GC inlet device 204 may be operated to reject late eluting components by splitting or backflush flow. The ability to reject late eluters may facilitate the direct integration of the GC inlet device 204 with a low thermal mass GC column, and may eliminate the need for a guard column. This may facilitate the design of GC instruments with small footprints and low power requirements which, for example, are considerations for designing transportable and portable instruments. En addition, the effectiveness of the MCL 256 in separating components may enable selecting only a limited range of analytes from the sample injected into the GC inlet device 204 to thereafter pass on to the GC column (e.g., “heart cutting”).
As one non-limiting example of operating in the splitless mode, the flow of carrier gas 446 through the first carrier gas line 472 may be 4.5 mL/min and the flow 444 of sample-gas mixture through the first purge line 474 may be 3 mL/min (resulting in a flow of 1.5 mL/min through the MCL 256), and the flow 448 of carrier gas through the second carrier gas line 480 may be 0.5 mL/min, resulting in a flow 442 of sample-gas mixture into the GC column 408 of 2 mL/min.
As one non-limiting example of operating in the split mode, the split ratio is set to 20:1. The flow 446 of carrier gas through the first carrier gas line 472 may be 33 mL/min and the flow 444 of sample-gas mixture through the first purge line 474 may be 3 mL/min, resulting in a flow of 30 mL/min through the MCL 256. The flow 448 of carrier gas through the second carrier gas line 480 may be 0.5 mL/min, and the flow 450 of sample-gas mixture through the second purge line 482 may be 28.5 mL/min, resulting in a flow 442 of sample-gas mixture into the GC column 408 of 2 mL/min.
As one non-limiting example of operating in the backflush mode, the flow 448 of carrier gas through the second carrier gas line 480 may be 15 mL/min, the flow 450 of gas through the second purge line 482 may be 4 mL/min, and the flow 442 of gas mixture into the GC column 408 may be 2 mL/min, resulting in a back flow of 9 mL/min through the MCL 256. The flow 446 of carrier gas through the first carrier gas line 472 may be 1 mL/min, resulting in a flow 444 of mixture through the first purge line 474 of 10 mL/min.
As one non-limiting example of operating in the cut/splitless injection mode, the flow of carrier gas 446 through the first carrier gas line 472 may be 4.5 mL/min, the flow 448 of carrier gas through the second carrier gas line 480 may be 3 mL/min, the flow 444 of sample-gas mixture through the first purge line 474 may be 3 mL/min, and the flow 450 of sample-gas mixture through the second purge line 482 may be 2.5 mL/min. This results in a net flow of 1.5 mL/min through the MCL 256 and a flow 442 of carrier gas into the GC column 408 of 2 mL/min.
As one non-limiting example of operating in the cut/split injection mode, the split ratio is set to 20:1. The flow of carrier gas 446 through the first carrier gas line 472 may be 33 mL/min, the flow 448 of carrier gas through the second carrier gas line 480 may be 3 mL/min, the flow 444 of sample-gas mixture through the first purge line 474 may be 3 mL/min, and the flow 450 of sample-gas mixture through the second purge line 482 may be 31 mL/min. This results in a net flow of 30 mL/min through the MCL 256 and a flow 442 of carrier gas into the GC column 408 of 2 mL/min.
The cut mode may be utilized when complete rejection of solvent or analyte components is desired, or when rejection is desired at lower flow rates. Generally, the split mode during normal injection does not eliminate solvent or components but rather attenuates them by the split ratio. In the case of the solvent, this can still amount to a large quantity of material being transferred to the GC column 408 after splitting. Moreover, the split mode during normal injection typically entails a large increase in flow rate through the liner column 254 that may lead to undesirable shifts in retention. If multiple splitting events are contemplated in a single chromatogram, the required timing of events becomes more empirical rather than being simple and self-evident based on the elution times in the initial chromatogram. For these reasons, there are situations in which it is more ideal to implement the above-described cut mode, in which elutions are unchanged and the components may be individually and quantitatively transferred to the GC column 408 and detector or rejected to the cut pathway.
The GC inlet device 204 of the GC inlet assembly 600 may generally be configured as described above. For example, the GC inlet device 204 may be operated in (and switchable between) the above-described splitless, split, backflush and cut modes. The GC inlet device 204 may also be configured for temperature control, such as for establishing a temperature gradient or controlling the temperature of individual zones, as described above. Additionally, the GC inlet device 204 may include an MCL as described above for performing separations prior to injecting the sample-carrier gas mixture into the GC column 408. In some applications, the provision of a separate vaporization device 504 may facilitate optimizing the desired operation of the GC inlet device 204 by decoupling the primary vaporization function from the GC inlet device 204. It will be understood that one or more features of the above-described GC inlet device 204 may be eliminated if they are duplicative of features provided by the vaporization device 604.
Exemplary embodiments provided in accordance with the presently disclosed subject matter include, but are not limited to, the following:
1. A gas chromatograph (GC) inlet device, comprising: an inlet chamber; a sample inlet communicating with the inlet chamber; a carrier gas inlet communicating with the inlet chamber; a liner chamber comprising a first end communicating with the inlet chamber and an axially opposing second end; a plurality of parallel capillaries disposed in the liner chamber; an outlet chamber communicating with the second end; and an outlet port communicating with the outlet chamber for coupling with a GC column.
2. The GC inlet device of embodiment 1, comprising a filler material occupying interstices between the capillaries, wherein the filler material prevents fluid flow between the capillaries.
3. The GC inlet device of embodiment 1 or 2, wherein the capillaries comprise a stationary phase disposed in interiors of the capillaries.
4. The GC inlet device of any of embodiments 1-3, comprising a temperature controller configured for controlling temperature at one or more regions of the GC inlet device.
5. The GC inlet device of embodiment 4, wherein the temperature controller comprises a multi-zone heater configured for independently heating different zones along a length of the GC inlet device.
6. The GC inlet device of embodiment 4, wherein the temperature controller is configured for independently controlling a temperature of the inlet chamber and a temperature of the liner chamber.
7. The GC inlet device of any of embodiments 1-6, wherein the carrier gas inlet is a first carrier gas inlet, and further comprising a second carrier gas inlet communicating with the outlet chamber.
8. The GC inlet device of any of embodiments 1-7, comprising a first purge outlet communicating with the inlet chamber, a second purge outlet communicating with the outlet chamber, or both a first purge outlet and a second purge outlet.
9. The GC inlet device of any of embodiments 1-8, comprising a flow control system switchable between two or more modes of operation selected from the group consisting of a normal injection mode, a normal splitless mode, a normal split mode, a backflush mode, a cut mode, a cut splitless mode, and a cut split mode.
10. The GC inlet device of any of embodiments 1-9, comprising a purge vent communicating with the outlet chamber, and a flow control system switchable between a splitless mode and a split mode, wherein at the splitless mode fluid flowing from the liner chamber is prevented from flowing to the split vent, and at the split mode at least some of the fluid flowing from the liner chamber flows to the split vent.
11. The GC inlet device of any of embodiments 1-10, wherein the carrier gas inlet is a first carrier gas inlet, and further comprising a second carrier gas inlet communicating with the outlet chamber, a purge vent communicating with the inlet chamber, and a flow control system switchable between a normal injection mode and a backflush mode, wherein: at the normal injection mode the flow of carrier gas through the first carrier gas inlet is higher than the flow of carrier gas through the second carrier gas inlet; and at the backflush mode the flow of carrier gas through the second carrier gas inlet is higher than the flow of carrier gas through the first carrier gas inlet, and a net flow of carrier gas is directed from the outlet chamber, through the liner chamber, through the inlet chamber, and to the purge vent.
12. The GC inlet device of any of embodiments 1-11, wherein the carrier gas inlet is a first carrier gas inlet, and further comprising a second carrier gas inlet communicating with the outlet chamber, a purge vent communicating with the outlet chamber, and a flow control system switchable between a normal injection mode and a cut mode, wherein: at the normal injection mode the flow control system adjusts respective flows of carrier gas through the first carrier gas inlet and the second carrier gas inlet such that a substantial portion of fluid flowing through the liner chamber flows through the outlet port; and at the cut mode the flow control system adjusts the respective flows such that substantially all of the fluid flowing through the liner chamber is diverted away from the outlet port and directed to the purge vent.
13. A gas chromatograph (GC), comprising: the GC inlet device of any of embodiments 1-12; and a GC column communicating with the outlet port.
14. A gas chromatograph (GC) inlet assembly, comprising: a vaporization device comprising: a vaporization chamber; a carrier gas inlet communicating with the vaporization chamber; a heater configured for heating the vaporization chamber; and a first outlet port communicating with the vaporization chamber; and a GC inlet device comprising: an inlet chamber communicating with the first outlet port; a sample inlet communicating with the inlet chamber; a liner chamber comprising a first end communicating with the inlet chamber and an axially opposing second end; a plurality of parallel capillaries disposed in the liner chamber; an outlet chamber communicating with the second end; and a second outlet port communicating with the outlet chamber for coupling with a GC column.
15. A method for introducing a sample to a gas chromatograph (GC) chamber, the method comprising: flowing a sample and a carrier gas through a liner chamber; separating components of the sample by flowing the sample through a plurality of parallel capillaries disposed in the liner chamber; and flowing the sample from the liner chamber to the GC column.
16. The method of embodiment 15, comprising vaporizing the sample before flowing the sample to the GC column.
17. The method of embodiment 15 or 16, comprising heating the sample before flowing the sample to the GC column according to a mode selected from the group consisting of: heating an inlet chamber from which the sample flows to the liner chamber; heating the liner chamber; heating an inlet chamber from which the sample flows to the liner chamber, and heating the liner chamber at a different temperature than the inlet chamber; heating two or more zones along a length of the liner chamber at different temperatures; and a combination of two or more of the foregoing.
18. The method of any of embodiments 15-17, comprising controlling a temperature of the capillaries, and controlling a temperature of a zone upstream of the capillaries such that the capillaries are maintained at a lower temperature than the upstream zone.
19. The method of any of embodiments 15-18, comprising conducting a first flow of the carrier gas into an inlet chamber upstream of the liner chamber, and conducting a second flow of the carrier gas into an outlet downstream of the liner chamber.
20. The method of any of embodiments 15-19, comprising flowing at least a portion of the sample from the liner chamber through a purge vent.
21. The method of any of embodiments 15-20, comprising switching between a split mode and a splitless mode, wherein the split mode comprises flowing at least a portion of the sample from the liner chamber into an outlet chamber, and through a purge vent instead of to the GC column, and the splitless mode comprises flowing the sample through the outlet chamber and to the GC column without flowing the sample through the purge vent.
22. The method of any of embodiments 15-21, comprising switching between a normal flow mode and a back flush mode, wherein the normal flow mode comprises flowing the carrier gas to an inlet chamber, through the liner chamber and to an outlet chamber, and the back flush mode comprises flowing the carrier gas directly to the outlet chamber such that the sample eluting from the liner chamber is diverted to a purge valve.
23. The method of any of embodiments 15-22, comprising switching between a normal flow mode and a cut mode, wherein the normal flow mode comprises flowing the carrier gas to an inlet chamber, through the liner chamber and to an outlet chamber, and the cut mode comprises flowing the carrier gas to the inlet chamber and to the outlet chamber such that the sample eluting from the liner is diverted to a purge valve.
24. The method of any of embodiments 15-23, comprising, before flowing the sample and the carrier gas through the liner chamber, flowing the sample and the carrier gas through a vaporization device.
25. A gas chromatograph (GC) inlet device configured for performing the method of any of embodiments 15-24.
It will be understood that terms such as “communicate” and “in . . . communication with” (for example, a first component “communicates with” or “is in communication with” a second component) are used herein to indicate a structural, functional, mechanical, electrical, signal, optical, magnetic, electromagnetic, ionic or fluidic relationship between two or more components or elements. As such, the fact that one component is said to communicate with a second component is not intended to exclude the possibility that additional components may be present between, and/or operatively associated or engaged with, the first and second components.
It will be understood that various aspects or details of the invention may be changed without departing from the scope of the invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation—the invention being defined by the claims.
