TECHNICAL FIELD

[0001] The present invention relates to liners provided in the inlets of gas chromatography (GC) instruments, which inlets are provided upstream of the columns utilized to separate samples under study into constituent components.

BACKGROUND

[0002] Gas chromatography (GC) entails the analytical separation of a vaporized or gas-phase sample that is injected into a chromatographic column. The GC column is typically housed in a thermally controlled oven. A carrier gas, such as helium, nitrogen, argon, or hydrogen, is utilized as the mobile phase for elution of the analyte sample in the column. Before introduction to the column, the sample and carrier gas may be separately introduced into a GC injection port (also referred to as a GC inlet) coupled to the column head. In the GC injection port, the sample is injected into the carrier gas stream and the resulting sample-carrier gas mixture flows through the column. The typical GC injection port is configured for vaporizing an initially liquid-phase sample. The GC injection port may include a liner configured for performing and optimizing the vaporization. The liner is typically a cylindrical tube positioned in the path taken by the sample- carrier gas mixture to the outlet of the GC injection port. From the GC injection port, the vaporized sample is then driven by the carrier gas flow into and through the column. During column flow the sample encounters a stationary phase (a coating or packing), which is formulated to cause 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 peak spectrum identifying the separated components may be constructed.

[0003] The performance of the GC injection port plays a key role in the overall performance of a GC -based instrument, including hybrid instruments such as a gas chromatograph-mass spectrometer (GC-MS). The performance of the GC injection port may affect issues such as, for example, peak resolution, detection limits, sample discrimination, and sample carryover. A key component of the GC injection port is the liner. The liner should be designed to ensure that an injected liquid sample is fully vaporized and is mixed with the carrier gas to form a homogeneous stream, in preparation for analytical separation in the column.

[0004] When a liquid sample is injected into a GC liner, particularly at high speed such as when using an auto-sampler, there is a chance that liquid droplets will reach and enter the GC column without being completely vaporized. This results in a non-homogeneous sample stream in the column, which may cause errors in the analysis of the sample performed by the GC instrument. A common solution to this problem is to insert glass wool in the liner. The glass wool can be effective in stopping liquid droplets and, due to the large total surface area presented by the glass fibers, can assist in the evaporation of the liquid sample. However, a packing of glass wool in a liner is inherently a non-uniform (non-homogeneous) structure in terms of its shape, amount or geometry, the flow passages it provides, and the surfaces it presents. That is, the glass fibers are randomly oriented and the density of the glass fibers (or spacing between adjacent fibers or sections of fiber) varies in any direction through the packing. Thus, the configuration of any given packing of glass wool cannot be repeated in another liner or in the same liner (for example, when replacing the glass wool with new glass wool). Moreover, the gas pressure (pressure pulse) in the liner changes during GC operation, which can push the glass wool up or down inside the liner from its original position. Variability in sample flow due to differences in the position of the glass wool inside the liner, and in the amount of glass wool provided in the liner, creates inconsistent chromatographic results. Additionally, the surfaces of the liner and the glass wool are typically deactivated to prevent reaction with (including adsorption of) samples and thereby achieve precise analyses. However, glass wool is very fragile and breaks easily. The broken and exposed surfaces are not deactivated, and hence can adsorb the sample and thereby create errors in the analysis.

[0005] An alternative to utilizing a glass wool packing is to insert a porous glass frit into the liner. The frit is shaped as a thin disk formed from multiple glass beads, such that the beads define pores through the thickness of the frit. However, the beads are small and hence the pores are small, such that the frit tends to becomes easily clogged and the pressure drop across the frit is disadvantageously large.

[0006] Therefore, there is a need for improved solutions in the configuration of GC liners. SUMMARY

[0007] 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.

[0008] According to one embodiment, a liner for a gas chromatograph (GC) injection port includes: a tube elongated along an axis and comprising an entrance opening, an exit opening, and a bore extending along the axis from the entrance opening to the exit opening, the bore having a cross-sectional flow area; and a plug positioned in the bore and spanning the entire cross-sectional flow area of the bore, the plug comprising an inlet side facing the entrance opening, an outlet side facing the exit opening, and a plurality of closely packed spherical beads, wherein: each bead comprises an outer surface, and the outer surface is deactivated; each bead is attached to one or more adjacent beads; at least some of the beads are attached to the tube; and the plug comprises a plurality of tortuous fluid flow paths running from the inlet side to the outlet side in voids between adjacent beads and between the tube and beads adjacent to the tube.

[0009] According to another embodiment, a liner for a gas chromatograph (GC) injection port includes: a tube elongated along an axis and comprising an entrance opening, an exit opening, and a bore extending along the axis from the entrance opening to the exit opening, the bore having a cross- sectional flow area, wherein the bore comprises a main bore section and a tapered section upstream of the main bore section, the tapered section has a diameter that reduces down to a minimum diameter less than a diameter of the main bore section, and the plug is positioned in the main bore section.

[0010] According to another embodiment, a gas chromatograph (GC) injection port includes: a sample inlet configured for receiving a needle; a sample outlet configured for coupling with a GC column; a housing configured for conducting a sample from the sample inlet to the sample outlet; a carrier gas inlet communicating with the housing; and a liner according to any of the embodiments disclosed herein, positioned in the housing in a fluid flow path between the sample inlet and the sample outlet.

[0011] According to another embodiment, a gas chromatograph (GC) system includes: a liner according to any of the embodiments disclosed herein; a GC column in fluid communication with the exit opening. [0012] According to another embodiment, a method for injecting a sample into a gas chromatograph (GC) column includes: applying heat to a liner according to any of the embodiments disclosed herein; flowing a sample into the liner; flowing a carrier gas into the liner; flowing the sample and the carrier gas through the plurality of tortuous fluid flow paths and into contact with the beads, such that the beads transfer heat to the sample and the sample passes through the plurality of tortuous fluid flow paths without being analytically separated; and flowing the sample and the carrier gas from the liner via the exit opening into the GC column.

[0013] 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.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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.

[0015] Figure 1 is a schematic cross-sectional view of an example of a gas chromatograph (GC) injection port according to some embodiments of the present disclosure.

[0016] Figure 2 is a cross-sectional elevation view of an example of a GC liner according to an embodiment of the present disclosure.

[0017] Figure 3 is a cross-sectional elevation view of an example of a GC liner according to another embodiment.

[0018] Figure 4 is a cross-sectional elevation view of an example of a GC liner according to another embodiment.

DETAILED DESCRIPTION

[0019] Figure 1 is a schematic cross-sectional view of an example of a gas chromatograph (GC) injection port ( or liner) 100 according to some embodiments. The GC injection port 100 may generally include a sample inlet 104 configured for receiving a sample typically via a sample injection needle 108 (e.g., a syringe needle) communicating with a sample source (e.g., a vial), a sample outlet 112 configured for fluidic coupling with a GC column 116, a housing or shell 120 configured for conducting a sample from the sample inlet 104 to the sample outlet 112 and typically also heating the sample and vaporizing liquid-phase portions of the sample and solvent, and a carrier gas inlet (depicted by arrow 124) communicating with the housing 120. The GC inlet 100 generally may have any configuration now known or later developed that includes a vaporizing liner 164 (described further below). Thus, for example, the GC injection port 100 may be configured as a capillary direct inlet, a split inlet, a splitless inlet, a split/splitless inlet, a programmed-temperature vaporizer (PTV) inlet, etc.

[0020] When configured for use with a sample injection needle 108, the GC injection port 100 includes an inlet septum 128 positioned between the sample inlet 104 and an interior of the housing 120. The septum 128 functions as a leak-free seal that prevents air from entering the GC injection port 100 and maintains internal gas pressure in the GC injection port, and also prevents solid contaminants from entering the GC injection port 100. The septum 128 has an elastomeric composition that is sufficiently deformable to allow the septum 128 to form a fluid-tight seal under compression, to allow the needle 108 to be inserted through the entire thickness of the septum 128 without damaging the needle 108 or the septum 128 (e.g., coring, tearing, etc.), and to allow the septum 128 to re-seal itself upon removal of the needle 108. The outside diameter of the needle 108 typically is in a range from 34 to 18 gauge (0.19 mm to 1.27 mm), and may be either constant or tapering. If tapering, the range just given may refer to the maximum outside diameter of the needle 108.

[0021] As additional non-limiting examples of components of the GC injection port 100, the GC injection port 100 may include an upper assembly in which the septum 128 is mounted, and a lower assembly that may be mounted to a housing or bracket 132 of the GC instrument (e.g., the oven). The upper assembly may include a septum support 136 providing a seat on which the septum 128 is placed, and a septum nut 140 configured for being removably secured to the septum support 136 by any suitable means. For example, the septum nut 140 may include internal threads that mate with external threads of the septum support 136. The septum 128 may be installed by placing the septum 128 on the seat of the septum support 136 and threading the septum nut 140 onto the septum support 136. Depending on the embodiment, the septum 128 may be axially compressed to some degree between the septum nut 140 and the septum support 136. The septum nut 140 includes an opening serving as the sample inlet 104. A needle guide 144 may be provided in the opening.

[0022] The GC injection port 100 may also include an inlet chamber 148 in which the sample flow is merged with the carrier gas flow. In the illustrated example, the inlet chamber 148 is defined at least in part by the septum support 136. The carrier gas inlet 124 communicates with the inlet chamber 148. The septum support 136 also includes a bore between the outlet side of the septum 128 and the inlet chamber 148 to allow the needle 108 to access the inlet chamber 148 after penetrating the septum 128. In the illustrated embodiment, the GC inlet 100 also includes a septum purge outlet (depicted by arrow 152) communicating with the inlet chamber 148 as appreciated by persons skilled in the art.

[0023] The upper assembly may be removably secured to the lower assembly by any suitable means. For example, the upper assembly may include a lower nut 156 with internal threads that mate with external threads of a fitting 160 of the lower assembly.

[0024] In the illustrated embodiment, the GC inlet housing 120 is part of the lower assembly. A liner 164 is positioned in the housing 120 and an annular space 168 is defined between the outside of the liner 164 and inside surfaces of the housing 120 surrounding the liner 164. The liner 164 typically is configured as an elongated tube, and typically is composed of borosilicate glass. In the illustrated embodiment, the upper opening of the liner 164 communicates with the inlet chamber 148, and an O-ring 172 or other suitable sealing component fluidly isolates the inlet chamber 148 from the annular space 168. More generally, the liner 164 is positioned in the fluid flow path between the sample inlet 104 and the sample outlet 112. The GC inlet 100 may also include a temperature control device 176 of any suitable design. The temperature control device 176 includes a heating device, for example one or more resistive heating elements powered by an electrical power source and mounted in a thermally conductive heater block. In some embodiments, the temperature control device 176 may also include a cooling device. The temperature control device 176 may be mounted to the housing 120, or in any case is positioned in thermal contact with the liner 164, meaning that the temperature control device 176 is able to heat the sample/carrier gas mixture as it flows through the liner 164 and vaporize liquid-phase components. In the illustrated embodiment, the GC inlet 100 also includes a split flow outlet (depicted by arrow 180) communicating with the GC inlet interior (e.g., the annular space 168) to perform split-flow injection techniques, as appreciated by persons skilled in the art. [0025] The lower opening of the liner 164 may communicate with an outlet chamber 184 that in turn communicates with the annular space 168 and the sample outlet 112. The sample outlet 112 may be configured for coupling with the GC column 116 by any suitable means. Various hardware components that may be provided at the outlet end of the GC inlet 100, such as seals, ferrules, fittings, and the like, are known to persons skilled in the art and thus need not be described further herein. The GC column 116 is located in the housing (e.g., oven) of the GC instrument. Analytically separated components of the sample elute from the column 116 and flow to a detector, as depicted by an arrow 188.

[0026] Figure 2 is a cross-sectional elevation view of an example of a GC liner 264 according to an embodiment of the present disclosure. The liner 264 may be provided in a GC inlet such as the GC inlet 100 described above and illustrated in Figure 1. The liner 264 includes a tube 206 elongated along its central axis and a plug 210 of beads 214 positioned in the tube 206.

[0027] The tube 206 is generally configured as a straight cylinder. The tube 206, as a hollow body, coaxially surrounds an internal bore 218 that defines a fluid flow path from an entrance opening 222 at one axial end of the tube 206 to an exit opening 226 at the other axial end of the tube 206. In some embodiments the tube 206 is composed of borosilicate glass, while in other embodiments the tube 206 may be composed of another material of sufficient thermal conductivity. Typically, the axial length of the tube 206 is on the order of millmeters (mm). As one non-limiting example, the axial length of the tube is dictated by the dimensions of the injection port 100 but are typically in a range from 70 mm to 80 mm. Typically the diameter of the bore 218 (i.e., the inside diameter of the tube 206) is on the order of millimeters (mm). As one non-limiting example, the internal diameter of the bore 218 is in a range from 1 mm to 4 mm. In the present embodiment, the diameter of the bore 218 is constant along the entire length of the tube 206. In other embodiments, the diameter of the bore 218 may vary (e.g., taper) along one or more axial sections of the tube 206. In the latter case, the numerical examples of the diameter of the bore 218 just specified may be taken as corresponding to the maximum diameter of the bore 218.

[0028] The plug 210 is formed of a plurality of closely packed spherical beads 214. In some embodiments the beads 214 are composed of borosilicate glass, while in other embodiments the beads 214 may be composed of another material of sufficient thermal conductivity. The beads 214 are uniformly sized, typically having a diameter on the order of a few millimeters (e.g., 2 mm). As one non-limiting example, the diameter of the beads 214 is in a range from 0.5 mm to 3 mm. As one non-limiting example of uniformly sized beads 214, the diameter of the beads 214 may vary by +/- 10 % of the average diameter. The number of beads 214 making up the plug 210 may vary, depending on the diameter of the beads 214 and the diameter of the bore 218. As one non-limiting example, the number of beads 214 is in a range from 6 to 20.

[0029] In the illustrated embodiment, the number of beads 214 is small enough (or the size of the beads 214 is large enough) that each bead 214 contacts the inside surface of the tube 206. In other embodiments, some of the beads 214 may not contact the inside surface of the tube 206. In such case, the plug 210 may be considered as including "outer" beads 214 that contact the inside surface of the tube 206 and "inner" beads that do not contact the inside surface of the tube 206 (i.e., the outer beads 214 are between the inner beads and the inside surface of the tube 206).

[0030] The beads 214 fill in a section of the cylindrical bore 218 of the tube 206. As such, the plug 210 is generally cylindrical-shaped. The aspect ratio (axial length to outer diameter) of the plug 210 may vary in different embodiments. In the illustrated embodiment, the axial length of the plug 210 (along the axis of the tube 206) is greater than the outer diameter of the plug 210. In other embodiments, the axial length of the plug 210 may be less than the outer diameter of the plug 210. That is, from the perspective of Figure 2, the plug 210 may be disk-shaped (e.g., like a hockey puck).

[0031] The axial position of the plug 210 within the bore 218 of the tube 206 may be fixed by any suitable mechanical, chemical, or thermal method. For example, the plug 210 may be held in position between two restrictions formed on the inside surface of the tube 206 (not shown). As another example, the (outer) beads 214 of the plug 210 may be adhered to the inside surface of the tube 206 by a suitable adhesive. As another example, the (outer) beads 214 of the plug 210 may be fused to the inside surface of the tube 206 by a heating process. Each bead 214 may be attached to adjacent beads 214 by thermal fusion or other technique. The technique employed to attach the beads 214 to each other may be the same as or different from the technique employed to attach the plug 210 to the inside surface of the tube 206.

[0032] In some embodiments, the plug 210 first may be formed by attaching the beads 214 to each other, separately from the tube 206. The plug 210 may then be inserted into the tube 206, after which the plug 210 may be attached to the inside surface of the tube 206. In other embodiments, the plug 210 may be formed and secured inside the tube 206 (i.e., the beads 214 may be attached to each other and to the inside surface of the tube 206) simultaneously in a single process. As an example of the latter process, the beads 214 may be inserted into the tube 206 and held in a closely packed arrangement at the desired axial position, which for example may be assisted by the use of appropriate tools. Then the tube 206 with the beads 214 therein may be placed in an oven and subjected to an appropriate temperature program by which the beads 214 are thermally fused together and to the inside surface of the tube 206.

[0033] As a further processing step, the beads 214 may be fabricated so as to be porous or dimpled. A porous bead provides significantly more surface area than a non-porous bead of the same size. Thus the beads 214 when porous expose the sample to more surface area and thereby are able to more effectively transfer heat to the sample, resulting in more complete evaporation of droplets and a more homogeneous sample stream. As one non-limiting example, the average pore size (diameter) may be in a range from about 60 Angstroms (A) to about 500 A. As one non- limiting example, the average surface area of the pores may be in a range from about 40 m ² /g to about 500 m ² /g. Generally any process for fabricating the beads 214, including porous beads, now known or later developed, may be employed. In some embodiments, the beads 214 may be fabricated so as to have solid cores surrounded by porous shells. The process employed to fabricate the beads 214 may be one that results in the beads 214 having a narrow size distribution, i.e., the beads 214 have the same or substantially the same diameter. Hence, the beads 214 may be characterized as being uniformly sized as noted above. In the case of porous beads, the fabrication process may be one that results in the pores having a narrow size distribution. As one non-limiting example of uniformly sized pores, the diameter of the pores may vary by +/- 500 % of the average diameter. Thus the overall structure or geometry of the plug 210, whether or not the beads 214 are porous, is uniform or homogeneous.

[0034] As a further processing step, the tube 206 and the plug 210 may be subjected (together or separately) to a deactivation process by which at least the inside surface of the tube 206 defining the bore 218 and the outside surfaces of the beads 214 become deactivated. In the present context, a "deactivated" surface is one that is chemically inert (will not react with the sample or carrier gas) and does not exhibit any appreciable chromatographic or analytical separation activity. Hence, the sample when contacting the surface of the tube 206 and contacting the beads 214 will not be retained by, or exhibit affinity for, the surface of the tube 206 or the beads 214. Consequently, the sample will pass through the liner 264 (including through the plug 210) and enter the GC column 116 (Figure 1) "intact," i.e., without having been separated into different fractions. Generally any process for deactivation may be employed depending on the material of the tube 206 and the beads 214 such as, for example, silanization in the case of borosilicate glass as appreciated by persons skilled in the art.

[0035] The presently disclosed plug 210 is configured as a three-dimensional, cylindrically- shaped grouping or ensemble of closely-packed spherical beads 214 attached to each other, and attached to the inside surface of the tube 206 or retained in place by mechanical means. In the plane transverse to the axis of the tube 206, the plug 210 spans the entire cross-sectional flow area of the bore 218 of the tube 206. The plug 210 has an inlet side facing the entrance opening 222 of the tube 206, an outlet side facing the exit opening 226 of the tube 206, and an axial length (or depth) between the inlet side and the outlet side. By this configuration, the plug 210 defines a plurality of tortuous or labyrinthine fluid flow paths from the inlet side to the outlet side, i.e., the fluid flow paths change direction multiple times. The fluid flow paths are formed by the voids or interstices between neighboring beads 214 and between the inside surface of the tube 206 and beads 214 adjacent thereto. Consequently there is no line-of- sight between the entrance opening 222 and the exit opening 226 of the tube 206, and thus no line-of-sight between the sample injection needle 108 and the GC column 116 (Figure 1). Because the beads 214 have the same size, the exact number of beads 214 utilized and their arrangement (positions relative to each other and to the tube 206) can be easily repeated from one plug 210 to another, allowing the fabrication or assembly of the plug 210 to be precisely repeatable. Moreover, while the many tortuous flow paths provided in a given plug 210 are different from each other on an individual basis, the overall configuration of the system of tortuous flow paths in the plug 210 (the number, size, and geometry of the flow paths) is uniform and repeatable, and the resulting pressure drop through the plug 210 is repeatable. Further, the plug 210 has a large overall surface area and high thermal mass. The foregoing features and properties result in the plug 210 being highly effective in stopping and vaporizing liquid droplets, and catching and collecting the matrix materials from the injected sample. Consequently the plug 210 is effective in creating a homogeneous sample stream and improving the reproducibility of sample analyses.

[0036] In some embodiments, the beads 214 may have more than one distinct size. For example, the beads 214 may include first beads having a first size (first diameter) and second beads having a second size (second diameter). In such case, the first size is uniform (narrow polydispersity) and the second size is likewise uniform, and the beads of the first size and the second size may be arranged in the plug 210 in an overall uniform and repeatable manner.

[0037] Particularly in comparison to a glass wool packing or a porous glass frit, the pressure drop across (through the axial thickness of) the plug 210 (and thus the flow resistance) is lower than the pressure drop across a glass wool packing a porous glass frit. As an example, the pressure drop across a liner was measured several times for each of three configurations: a liner with a fully open bore (without either a multiple-bead plug as described herein or a glass wool packing), the same liner with a multiple-bead plug as described herein, and the same liner with a typical glass wool packing. For the liner with a fully open bore, the mean pressure drop was 19.202 psia (pounds per square inch absolute) and the median pressure drop was 19.240 psia. For the same liner with a multiple-bead plug as described herein, the mean pressure drop was 19.414 psia and the median pressure drop was 19.410 psia. For the same liner with a glass wool packing, the mean pressure drop was 19.954 psia and the median pressure drop was 19.860 psia. As noted earlier in this disclosure, the pressure dropt across a conventional porous glass frit with smaller beads and pores would be much more significant.

[0038] As additional advantages, because the configuration of the plug 210 is repeatable, particularly in comparison to the highly random orientation of the fibers of a glass wool packing, the use of the plug 210 may reduce the time and effort required for calibration. The position of the plug 210 and each bead 214 thereof in the tube 206 is securely fixed and not affected by the gas flow or gas pressure pulses. The beads 214 are not prone to breakage or damage, and hence the plug 210 may remain deactivated for a longer period of time in comparison to a glass wool packing.

[0039] In the present embodiment, as well as in the embodiments shown in Figures 3 and 4 (described below), the plug 210 is positioned at or proximate to the exit opening 226 of the tube 206. Alternatively the plug 210 may be positioned farther upstream, such as at or proximate to the central axial position (middle elevation) of the bore 218. More generally, no limitation is placed on the axial position of the plug 210 within the tube 206, other than for embodiments in which the sample injection needle 108 (Figure 1) is actually inserted into the tube 206. In these latter embodiments, the plug 210 should be located at an axial distance from the entrance opening 222 that is great enough to avoid being impacted by the tip of the needle 108.

[0040] Figure 3 is a cross-sectional elevation view of an example of a GC liner 364 according to another embodiment of the present disclosure. The liner 364 may be provided in a GC inlet such as the GC inlet 100 described above and illustrated in Figure 1. Like the liner 264 described above and illustrated in Figure 2, the liner 364 includes an elongated tube 306 surrounding an internal bore 318 that defines a fluid path from an entrance opening 322 to an exit opening 326, and a plug 310 of beads 314 positioned in the tube 306. In the present embodiment, the tube 306 is configured such that the bore 318 includes a main bore section 330 and a reduced-diameter bore section (or flow- restricting section) 334. The plug 310 is positioned in the main bore section 330. The diameter of the main bore section 330 is constant along its axial length. The diameter of the reduced-diameter bore section 334 is less than that of the main bore section 330, thereby providing a gas flow restriction in the liner 364. The reduced-diameter bore section 334 may assist in focusing the vaporized sample onto the GC column by minimizing the volume between the internal liner wall and the GC column. The main bore section 330 may include the entrance opening 322, i.e., the upstream end of the main bore section 330 may correspond to the entrance opening 322. The reduced-diameter bore section 334 may include the exit opening 326, i.e., the downstream end of the reduced-diameter bore section 334 may correspond to the exit opening 326. In the embodiment specifically illustrated in Figure 3, the reduced-diameter bore section 334 includes a converging (tapered) portion 338 and a constant-diameter portion 342. The converging portion 338 starts at the downstream end of the main bore section 330, and provides a transition between the larger diameter of the main bore section 330 and the smaller diameter of the constant-diameter portion 342. The reduced-diameter bore section 334 may further include a diverging portion 346 that provides a transition between the constant-diameter portion 342 and the outlet section of a GC inlet in which the liner 364 is installed and/or a fitting fluidly coupled to a GC column head.

[0041] In some embodiments, the liner 364 may have a double-taper configuration in which a reduced-diameter bore section similar to the reduced-diameter bore section 334 is also provided at the inlet end of the tube 306.

[0042] Figure 4 is a cross-sectional elevation view of an example of a GC liner 464 according to another embodiment of the present disclosure. The liner 464 may be provided in a GC inlet such as the GC inlet 100 described above and illustrated in Figure 1. Like the liners 264 and 364 described above and illustrated in Figures 2 and 3, the liner 464 includes an elongated tube 406 surrounding an internal bore 418 that defines a fluid path from an entrance opening 422 to an exit opening 426, and a plug 410 of beads 414 positioned in the tube 406. In the present embodiment, the tube 406 is configured such that the bore 318 includes a main bore section 430 and a tapered section 450 upstream of the main bore section 430. The plug 410 is positioned in the main bore section 430. The diameter of the main bore section 430 is constant along its axial length. The tapered section 450 may include the entrance opening 422, i.e., the upstream end of the tapered section 450 may correspond to the entrance opening 422. The tapered section 450 includes a converging portion 454 and a minimum-diameter portion (or needle wiper portion) 458. The diameter of the bore 418 is gradually reduced from the diameter at the entrance opening 422 down to a minimum diameter at the minimum-diameter portion 458. The tapered section 450 may also include a diverging portion 462 that provides a transition between the smaller diameter of the minimum-diameter portion 458 and the larger diameter of the main bore section 430.

[0043] The tapered section 450 may serve as a guide for a sample injection needle 108 (Figure 1), which may be inserted into the bore 318 via the entrance opening 422 for injecting the sample directly into the liner 464, so that the needle 108 is centered on the axis of the tube 406. The tapered section 450 may also serve as a wiper for the needle 108 to remove any contaminants or liquid remaining on the outside surface of the needle 108 after penetrating the septum 128 (Figure 1). The needle 108 is wiped by contacting the inside surface of the converging portion 454, or both the converging portion 454 and the minimum-diameter portion 458, while the needle 108 is being inserted into the liner 464. The converging portion 454 may have an axial length sufficient to allow the slope of its taper (or angle of convergence) to be small, thereby allowing the needle 108 to make glancing contact with the inside surface rather than impacting the inside surface in a more direct or abrupt manner. The minimum-diameter portion 458 (e.g., the axial center thereof) may be positioned at an axial distance from the entrance opening 422 that is less than the maximum axial distance from the entrance opening 422 expected to be reached by the tip of the needle 108 after full insertion into the liner 464. As one non-limiting example, assuming the tip of the needle 108 is expected to reach 20 mm from the entrance opening 422, the minimum-diameter portion 458 may be positioned at 18 mm from the entrance opening 422.

[0044] As further illustrated in Figure 4, in some embodiments the tube 406 may also be configured such that the bore 418 includes a reduced-diameter bore section 434 downstream from the main bore section 430, as described above and illustrated in Figure 3. The reduced-diameter bore section 434 may include converging (tapering) portion 438, a constant-diameter portion 442, and a diverging portion 446, as described above and illustrated in Figure 3. [0045] 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.

[0046] 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.