Sample introduction for chromatographic analysis

Abstract

The present disclosure relates to a sample inlet liner for gas chromatography and a method of forming such a liner. The liner includes a tubular body defining an internal channel, and a preformed insert formed from preformed glass or quartz fibre sheet material, the preformed insert being disposed within the tubular body such that the insert extends across the internal channel and has a size and shape which is commensurate with or oversized relative to the dimensions of the internal channel.

Description

Sample introduction for chromatographic analysisField of the invention

[0001] The present invention relates to chromatographic analysis, and more particularly, to sample introduction for chromatographic analysis. More specifically, this invention is related to a sample inlet liner, a method of forming a sample inlet liner and related aspects. While the invention is described with reference to gas chromatography, the invention may also have application to chromatographic analysis of liquids and other compressible fluids.Background of the invention

[0002] Gas chromatography (GC) is the analytical separation of a 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.

[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.

[0004] A critical component of the GC injection port is the liner. The liner should 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.

[0005] When a liquid sample is injected into a GC liner, there is a possibility 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 inthe 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 of material, geometry, the topography of flow passages it provides, and the surface area 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).

[0006] The application of wool into the liner can be inconsistent. The packing of the liners requires a highly skilled technician and is a slow process. The wool inserts are a consumable item, good for about 50 - 300 injections, which means that the liners last for anything from one day to a week, depending upon the intensity of use. Therefore, the need for a highly skilled technician and the slow process of creating the liners and the high consumption rate means that liners are an expensive aspect of gas chromatography.

[0007] In view of the difficulties in creating the liners, variability in sample flow are created due to differences in the position of the glass wool inside the liner, and in the amount of glass wool provided in the liner. This creates inconsistent chromatographic results.

[0008] Additionally, the surfaces of the liner and the glass wool are typically chemically 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 chemically deactivated, and hence can adsorb the sample and thereby create errors in the analysis.

[0009] An alternative 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 become easily clogged and the pressure drop across the frit isdisadvantageously large. Further, the frit can be difficult to insert, and repeatability with a frit is known to be poor.

[0010] Therefore, there is a need for improved solutions in sample inlet liners for chromatographic analysis.

[0011] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and / or combined with other pieces of prior art by a skilled person in the art.Summary of the invention

[0012] In accordance with a first aspect of the present invention, there is provided, a method of forming a sample inlet liner for gas chromatography, the method including: providing a tubular body defining an internal channel; forming an insert from preformed fibre sheet material; and inserting the insert into the internal channel of the tubular body such that the insert extends across the internal channel; wherein the shape and size of the insert is commensurate with or oversized relative to the internal channel of the tubular body.

[0013] Preferably, the material used to form the insert is one of a preformed glass fibre sheet material or a preformed quartz fibre sheet material. In an embodiment, the preformed fibre sheet material is a glass microfibre material. In another embodiment, the preformed fibre sheet material is a quartz microfibre material. In an embodiment, the preformed glass fibre sheet material is a preformed glass fibre mat. In an embodiment, the preformed quartz fibre sheet material is a preformed quartz fibre mat.

[0014] In an embodiment, the preformed fibre sheet material can include a woven or nonwoven fibrous mat. For example, the glass fibre mat can include a woven or nonwoven fibrous glass mat. In another example, the quartz fibre mat can include awoven or nonwoven fibrous quartz mat. The fibrous mat may be felt-like or paper-like. The fibrous mat may contain a random arrangement of fibres. The fibres of the sheet material may be discrete or continuous. Preferably, the insert offers an array of interstices, channels, and the like that is sufficient to provide a tortuous path for a sample injected into the sample inlet liner. Preferably, the insert is suitable for temporary retention of the injected sample.

[0015] In an embodiment, the preformed glass fibre sheet material is formed substantially of borosilicate glass. In an embodiment, the preformed glass fibre sheet material is formed of about 100% borosilicate glass.

[0016] In an embodiment, the preformed quartz fibre sheet material is formed of a high purity quartz.

[0017] In an embodiment, the preformed fibre sheet material is binder-free.

[0018] The sheet material may be of uniform thickness. The sheet material may have a nominal thickness in the range of about 100 pm and about 2000 pm. In an embodiment, the nominal thickness of the sheet material is between about 250 pm and about 700 pm. Preferably, the nominal thickness of the sheet material is between about 350 pm and about 675 pm.

[0019] The sheet material may be consistent or uniform in bulk density and / or pore size. A suitable range for bulk density is between about 20 to about 500 g / m2. A suitable range for pore size is between about 0.1 pm and about 200 pm. Preferably, the pore size is between about 0.4 pm and about 50 pm.

[0020] In an embodiment, the insert is configured to provide a desired restriction of flow through the internal channel. In an embodiment, said desired restriction of flow enables fluid flow through the insert, but preferably mitigates against an undesired level of backpressure in the internal channel. Preferably, the insert is configured to provide a desired flow rate therethrough or through the internal channel. Preferably, the insert is configured to provide a desired differential pressure across the insert.

[0021] Preferably, the preformed fibre sheet material insert is formed of a uniform material having a substantially consistent bulk density, pore size and thickness.

[0022] Advantageously, provision of such an insert provides the benefit of repeatability to an extent that was not realisable with a random filamentary mass formed of glass wool. This allows for more accurate and consistent chromatographic results. Further, the preformed fibre sheet material insert can have a longer service life than glass wool, which is more fragile and prone to damage through repeat use.

[0023] One of the roles of the insert in the tubular body of the liner is to retain a quantity of a sample injected into the liner and thereby provide a diffusion path for the retained quantity of the injected sample. The insert thereby assists with the vaporisation of the liquid sample. Another role of the insert in the tubular body of the liner is to promote better mixing between the sample and the carrier gas. In an embodiment, the desired flow rate and / or desired differential pressure across the insert is such to achieve said retention of a quantity of a sample injected into the liner and provide said diffusion path for the retained quantity of the injected sample, thereby assisting with the vaporisation of the liquid sample and / or promoting better mixing between the sample and the carrier gas. In an embodiment, the desired restriction of flow through the internal channel is such to achieve said retention of a quantity of a sample injected into the liner and provide said diffusion path for the retained quantity of the injected sample, thereby assisting with the vaporisation of the liquid sample and / or promoting better mixing between the sample and the carrier gas.

[0024] In an embodiment, said forming the insert includes forming the insert by cutting, punching or otherwise shaping preformed fibre sheet material. By way of example, cutting or forming devices may include mechanical implements, laser cutting, or ultrasonic devices.

[0025] The insert may be shaped and sized to be commensurate with or oversized relative to the internal channel of the tubular body such that in traversing the tubular body, the peripheral edges of the insert make contact with the internal wall(s) of the internal channel. In an embodiment, the insert has a diameter between about 1 and about 2 times a diameter of the internal channel (effectively providing an interference fit) before insertion into the internal channel. Preferably, the insert has a diameter between about 1 and about 1 .5 times the diameter of the internal channel before insertion into the internal channel. The tubular body of the liner is intended for insertion in achromatographic column and will therefore be of a predetermined dimension dependent upon the manufacturer’s requirements for the chromatographic column. Liner sizes vary since each kind of chromatographic column requires a specific liner size. Manufacturers may produce a range of chromatographic columns each requiring a different liner size and thus given there are a number of different manufacturers, a range of different liner sizes will be required to meet the requirements of the market. Thus, for each liner, the shape and size of the insert will be predetermined and correlating to the dimensions of the internal channel.

[0026] Most, if not all chromatographic columns require a liner having a tubular body of circular cross-section (outside diameter). However, the invention need not be limited to such kinds of liners. Other shapes are possible, with corresponding insert shapes.

[0027] In a most preferred form of the invention, the insert is oversized for the dimensions of the internal channel. For example, consider a tubular body having a cylindrical bore, the insert will therefore be circular but have a diameter which exceeds the internal diameter of the cylindrical bore. In this way, the edges of the insert will abut the surface of the internal channel thereby forming a seal therewith. Preferably, the insert is inserted into the tubular body in a manner which creates a dished or concave shape. In this form, the outer periphery of an undersurface of the insert makes contact with the surface of the internal channel to thereby create the seal. For ease of reference, the side of the insert facing the direction of insertion into the channel is regarded as the “undersurface”, and the other side is regarded as the upper surface.

[0028] Depending upon the manner of insertion, the upper surface may therefore be concave while the undersurface is convex. Preferably, the insert is inserted into the tubular body by the use of an insertion tool. The insertion tool may be a polymer tube or rod. However other modes of insertion are also possible e.g. using pressurised air.

[0029] In an embodiment, said seal between the insert and the internal channel of the tubular body may be completely due to or substantially due to the oversized insert. In other embodiments, the seal between the insert and the internal channel of the tubular body may be, at least in part, formed by a suitable heat treatment, which creates a bond between the insert and the tubular body.

[0030] In an embodiment, said providing the tubular body includes providing two or more body portions that when brought together form said tubular body. For example, the tubular body may be formed of two half tubular portions that are bonded or otherwise connected together. In an embodiment, said seal between the insert and the internal channel of the tubular body is formed by positioning the seal between said two or more tubular portions, and bonding said two more tubular portions together with the insert therebetween.

[0031] The insert may be disposed as desired along the length of the tubular body. For example, the tubular body may include an obstruction, restriction or tapering of the internal channel. The insert may be disposed such as to lie against the obstruction, restriction or tapering of the internal channel. Where the insert lies against an obstruction, restriction or tapering of the internal channel then the insert need not be oversized compared to the dimensions of the internal channel. For example, the obstruction, restriction or tapering of the internal channel may define an annular seat for the insert which facilitates the formation of a seal between the seat and the insert, thereby obviating the need for an oversized insert to create a seal. However, a similar arrangement can be achieved with said oversized insert. The insert may be pushed along the tubular body until it reaches the obstruction, restriction or tapering.

[0032] A single insert may be positioned in the tubular body. Alternatively, a plurality of inserts may be stacked one atop the other to change the flow characteristics in the liner, providing a more tortuous path and better mixing of the liquid and gaseous phases in the liner. Stacking multiple inserts creates a larger bed thickness for the insert while facilitating repeatability. For example, a multiple of 4 inserts will have a quantifiable thickness and repeatability due to the predetermined thickness of the individual inserts. In contrast, it is difficult to create a wool insert from a random filamentary mass with reliable and repeatable characteristics of at least thickness, bulk density and / or pore size.

[0033] In another form of the invention, a plurality of inserts may be spaced along the liner. For example, the tubular body may include a plurality of obstructions, restrictions or taperings of the internal channel, wherein a respective insert is disposed such as to lie against a respective obstruction, restriction or tapering of the internal channel.

[0034] In another form of the invention, a plurality of inserts may be separated by one or more spacers. Spacers provide an improved mixing pathway and some simple chromatographic separation similar to plate chromatography. Typically speaking, the configurations / material selection for a spacer is that which creates negligible flow restriction. The spacer may be in the form of a cylindrical member separating adjacent spacers. For example, a spacer may comprise a tubular member. A spacer in this form will create negligible flow restriction. Furthermore, such a spacer can be formed from glass tube which is easily deactivated or from another inert material such as PTFE. Suitably, the spacer has a uniform cross-section. Furthermore, the spacer may provide even separation between the 2 adjacent inserts. For example, a tubular spacer may create an upper annular surface and a lower annular surface, each of which bear against a respective insert. However, uneven separation, for example created by inclined annular surfaces on the spacer, is also possible.

[0035] The spacers may be used singly to separate 2 adjacent inserts or there may be plural spacers stacked one upon the other to separate 2 adjacent inserts. A series of spaced inserts may be separated by spacers between respective adjacent inserts.

[0036] For a given liner, the spacers, may be all of the same form or a variety of different kinds may be used. In an alternative form, glass or quartz beads may act as spacers. A range of other materials including particulate materials may also serve as spacers, including glass rods, quartz rods, glass beads, quartz beads, silica-based sorbent, Chromasob & diatomaceous earth (with and without sorbents), tenax, molecular sieves, and polymeric sorbent materials like porapak.

[0037] In an embodiment, a plurality of inserts provide the desired restriction of flow through the internal channel. In an embodiment, a plurality of inserts provide the desired flow rate through the internal channel.

[0038] In an embodiment, the method further includes deactivating surface(s) of the preformed fibre sheet material insert. In an embodiment, the method further includes deactivating surface(s) of the tubular body. In an embodiment, said deactivating surface(s) of the preformed fibre sheet material insert occurs before inserting the insert into the internal channel of the tubular body. In an embodiment, said deactivating surface(s) of the tubular body occurs before inserting the insert into the internal channelof the tubular body. In an embodiment, said deactivating surface(s) of the preformed fibre sheet material insert and said deactivating surface(s) of the tubular body occur after inserting the insert into the internal channel of the tubular body, thereby deactivating said surfaces at the same time. In an embodiment, said deactivating surface(s) of the preformed fibre sheet material insert and / or said deactivating surface(s) of the tubular body include performing silanization.

[0039] In an embodiment, the tubular body includes retention formation configured to inhibit movement of the insert when the liner is in use. Preferably, the retention formation is configured to substantially prevent dislodgement of the insert from the internal channel (or from a predetermined position within the internal channel) when the liner is in use. For example, the retention formation is configured to substantially prevent dislodgement of the insert from the internal channel due to pressure release and / or backpressure through the internal channel. Preferably, the retention formation is configured to substantially prevent dislodgement of the insert from the internal channel when the internal channel experiences up to about 5 psi, preferably up to about 10 psi, and further preferably up to about 20 psi. Advantageously, the retention formation enables the liners to be used in high pressure applications without concern for the retention of the insert in the predetermined or desired position within the internal channel.

[0040] The retention formation may include an obstruction, restriction or tapering of the internal channel. Preferably, the retention formation is disposed upstream of the insert. For example, the retention formation may be disposed above the insert (when positioned in the internal channel). The retention formation may be in the form of one or more dimples extending into the internal channel. The retention formation may be disposed directly adjacent to the upper surface of the insert. In other words, at least a portion of the retention formation may directly contact the upper surface of the insert. In an alternative embodiment, the retention formation may be spaced from the upper surface of the insert in a manner that substantially prevents dislodgement of the insert from the internal channel, but in which there is no direct contact between a portion of the retention formation and the upper surface of the insert. It will be appreciated that in such an embodiment, there would only be a relatively limited range of movement of theinsert tolerated before such movement of the insert begins to impact the repeatability and reliability of the liner.

[0041] In an embodiment, the method includes forming the retention formation of the tubular body. In an embodiment, said forming the retention formation includes heating the tubular body at a first location, and pushing the tubular body inwardly at the first location to form a dimple extending into the internal channel. In a preferred embodiment, said forming the retention formation includes heating the tubular body at first and second opposed locations, and pushing the tubular body inwardly at the first and second opposed locations to form a pair of opposed dimples extending into the internal channel. It will be appreciated that one or more further dimples may be formed by heating the tubular body at one or more additional locations around the circumference of the tubular body on which the first and second locations are located. In an embodiment, said forming the retention formation includes heating the tubular body at a first circumferential location, and pushing the tubular body radially inwardly at the first circumferential location to form an annular ring extending into the internal channel. In an embodiment, a pin or other structure is used to conduct said pushing. In an embodiment, said heating is conducted by a robotic heating process.

[0042] Preferably, said retention formation is formed after inserting the insert into the internal channel. However, it will be appreciated that in some embodiments the retention formation can be formed before inserting the insert into the internal channel. In one example, the retention formation may be formed as part of forming the tubular body.

[0043] It will be understood that references herein to an effect provided by a single insert in the internal channel can instead be provided by a plurality of inserts.

[0044] In accordance with a second aspect of the present invention, there is provided, the use of glass or quartz fibre sheet material having thickness in the range of about 100 pm to about 2000 pm and pore zone in the range of about 0.1 pm to about 200 pm in the manufacture of a liner for introducing a sample in gas chromatography.

[0045] Any of the features described above in accordance with the first aspect of the invention may have application to the second aspect.

[0046] In accordance with a third aspect of the present invention, there is provided an insert for a sample inlet liner for gas chromatography, wherein the insert is comprised of glass or quartz fibre sheet material having thickness in the range of about 100 pm to about 2000 pm and pore zone in the range of about 0.1 pm to about 200 pm.

[0047] Any of the features described above in accordance with the first or second aspects of the invention may have application to the third aspect.

[0048] In accordance with a fourth aspect of the present invention, there is provided, a sample inlet liner for gas chromatography, the liner including: a tubular body defining an internal channel; and a preformed insert formed from preformed glass or quartz fibre sheet material, the preformed insert being disposed within the tubular body such that the insert extends across the internal channel and has a size and shape which is commensurate with or oversized relative to the dimensions of the internal channel.

[0049] Any of the features described above in accordance with the foregoing aspects of the invention may have application to the fourth aspect.

[0050] In accordance with a fifth aspect of the present invention, there is provided a sample inlet liner for gas chromatography, the liner including: a tubular body defining an internal channel; and a plurality of preformed inserts positioned within the internal channel, with at least two adjacent inserts being separated by one or more tubular spacers.

[0051] Any of the features described above in accordance with the foregoing aspects of the invention may have application to the fifth aspect.

[0052] In accordance with a sixth aspect of the present invention, there is provided, a method of forming a sample inlet liner for gas chromatography, the method including: providing a tubular body defining an internal channel; providing an insert formed of a preformed fibre sheet material; andinserting the insert into the internal channel of the tubular body such that the insert extends across the internal channel; wherein the shape and size of the insert is commensurate with or oversized relative to the internal channel of the tubular body.

[0053] In an embodiment, said providing the insert includes selecting an insert configured to provide a desired restriction of flow through the internal channel. In an embodiment, said providing the insert includes selecting an insert configured to provide a desired flow rate therethrough or through the internal channel. In an embodiment, said providing the insert includes selecting an insert configured to provide a desired differential pressure across the insert.

[0054] Any of the features described above in accordance with the foregoing aspects of the invention may have application to the sixth aspect.

[0055] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

[0056] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

[0057] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.Brief description of the drawings

[0058] In order that the invention may be more fully understood, some embodiments will now be described, by way of example, with reference to the figures in which:

[0059] Figure 1 is a diagram of a sheet of glass microfiber from which a plurality of inserts may be cut or punched, in accordance with a preferred embodiment of the present invention;

[0060] Figure 2 is a detailed view of an insert received within a tubular body of a liner, showing the preferred configuration within the tubular body;

[0061] Figure 3A is diagrammatic view of a sample inlet liner for gas chromatography, in accordance with a first preferred embodiment of the invention;

[0062] Figure 3B is diagrammatic view of a sample inlet liner for gas chromatography, in accordance with a second preferred embodiment of the invention;

[0063] Figure 3C is diagrammatic view of a sample inlet liner for gas chromatography, in accordance with a third preferred embodiment of the invention;

[0064] Figure 3D is diagrammatic view of a sample inlet liner for gas chromatography, in accordance with a fourth preferred embodiment of the invention;

[0065] Figure 3E is diagrammatic view of a sample inlet liner for gas chromatography, in accordance with a fifth preferred embodiment of the invention;

[0066] Figure 3F is diagrammatic view of a sample inlet liner for gas chromatography, in accordance with a sixth preferred embodiment of the invention;

[0067] Figure 3G is a diagrammatic view of a sample inlet liner for gas chromatography, in accordance with a seventh preferred embodiment of the invention;

[0068] Figure 4 is a graph showing a comparison of RRF between a glass sheet liner and quartz wool liner for the 11 compounds analysed;

[0069] Figure 5 is a table comparing peak area analysis between a glass sheet liner and quartz wool liner for the 11 compounds analysed;

[0070] Figure 6 is a graph comparing endrin / DDT breakdown results between different liners;

[0071] Figure 7 is a table comparing results of a repeatability test between wool and sheet liners;

[0072] Figure 8 shows results of gas chromatography for a 1stand 50thinjection of a soil sample using different liners;

[0073] Figure 9 is a table comparing intra-liner results for each pesticide of the soil samples with different liners;

[0074] Figure 10 is a graph comparing intra-liner results based on Figure 9;

[0075] Figure 11 is a diagrammatic view of a sample inlet liner for gas chromatography, in accordance with another embodiment of the invention;

[0076] Figure 12 is a table comparing results of a test between quartz wool and quartz sheet liners;

[0077] Figure 13 provides chromatograms from a test showing the accuracy of a quartz sheet liner in analysing an avocado acetonitrile extract spiked with a pesticides mix;

[0078] Figure 14 provides a comparison of peak area trends from a test for each of a quartz sheet liner, wool liner and glass frit liner;

[0079] Figure 15 provides comparative chromatograms from a test for each of a quartz sheet liner, wool liner and glass frit liner;

[0080] Figure 16 provides a table comparing the results from a test that used the quartz sheet liners and quartz wool liners;

[0081] Figure 17 provides comparative data showing the performance of split quartz sheet liners and split quartz wool liners during a test; and

[0082] Figures 18A-18C are tables comparing results of repeatability testing for a quartz sheet liner across three batches.Detailed description of the embodimentsPreformed sheet material

[0083] In a preferred embodiment of the invention shown in Figure 1 , the inserts 10 may be cut or punched from a sheet of glass microfibre 11 . The sheet of glass microfibre 11 may be commercially available such as the glass microfiber filters sold by Whatman™. In this embodiment, the inserts 10 are circular in plan, thereby forming a flat circular disc. The inserts 10 have a diameter which is oversized for the tubular body of a liner for which it is intended. Since there are a number of manufacturers producing chromatographic apparatus requiring different sized liners, the inserts 10 will be produced in a range of different sizes. A standard known liner has an internal diameter of about 3.8 mm, and in such a case a suitable insert may have a diameter of about 4 mm. These values are exemplary only.

[0084] As will be appreciated from Figure 1 , the inserts are cut from a flat sheet 1 1 and therefore are initially flat or planar in configuration and shaped as circular discs. The inserts 10 are inserted into the internal channel 12 of the tubular body 13 using a pusher tube or rod (not shown). Since the inserts 10 are oversized for the tubular body 13, they will typically adopt a dished configuration within the tubular body 13, as illustrated in Figure 2. Typically, this produces a convex configuration facing the direction of insertion, with a concave configuration facing the opposite direction. The peripheral edge 18 along the undersurface of the insert 10 is thus engaged with the internal periphery 16 of the internal channel 12, thereby forming a seal with the internal periphery 16. This configuration enables a seal to be formed with the internal periphery 16 of the tubular body 13 while maintaining the insert thickness. Control over the insert thickness while maintaining an effective seal affords creation of a liner having the benefit of repeatability to an extent that was not realisable with a random filamentary mass formed of glass wool. It will be appreciated that the forming of a seal between the insert 10 and the internal periphery 16 creates friction which helps retain the insert 10 in the desired position. In some embodiments, a heat treatment process can be utilised to form a bond between insert 10 and internal periphery 16 of the internal channel 12.

[0085] The sheet material from which the inserts are cut or punched is binder-free glass microfiber in this embodiment. However, in alternative embodiments, the sheet material from which the inserts are cut or punched can be binder-free quartz microfiber. In yet another alternative embodiment, the sheet material from which the inserts are cut or punched can be binder-free carbon microfiber.

[0086] Table 1 illustrates typical properties of various grades of binder-free glass microfiber:

[0087] The preferred grade is GF / D as this has the largest filtration pore size, although the other grades can also be suitable depending on the desired application.

[0088] The sheet of glass microfiber 11 is of a uniform material having a substantially consistent bulk density, pore size and thickness. Advantageously, forming insert 10 from such a material provides the benefit of producing inserts of consistent property, but also repeatability in the production of inserts 10. Inserts 10, formed from the sheet of glass microfiber 11 , includes an array of interstices, channels, and the like that is sufficient to provide a tortuous path for a sample injected into the sample inlet liner. The insert assists with the vaporisation of the liquid sample, as well as promoting better mixing between the sample and the carrier gas.

[0089] Table 2 illustrates typical properties of various grades of binder-free quartz microfiber:

[0090] The preferred grade here is QM-A, although the other grades can also be suitable depending on the desired application.

[0091] Similar to the sheet of glass microfiber 11 mentioned above, a sheet of quartz microfiber is of a uniform material having a substantially consistent bulk density, pore size and thickness. Advantageously, forming insert 10 from such a material provides the aforementioned benefits of producing inserts of consistent property, but also repeatability in the production of inserts 10. Inserts 10, formed from the sheet of quartz microfiber, also includes an array of interstices, channels, and the like that is sufficient to provide a tortuous path for a sample injected into the sample inlet liner. The insert assists with the vaporisation of the liquid sample, as well as promoting better mixing between the sample and the carrier gas.Liner configurations

[0092] Figure 3 is a non-exhaustive set of various different forms for the sample inlet liner 20, each of which includes one or more inserts 10. Each of the various different forms is intended to suit a different application for gas chromatography. The various different forms arise from different configurations for the tubular body 13 and different insert and spacer arrangements. As will be appreciated, a large variety of differentforms could be created from the various different combinations and permutations of the tubular body, insert and spacer arrangements.

[0093] As known in the art, the tubular body 13 in each of the forms in Figure 3 is of glass construction. However, it will be appreciated that other forms of liner can be used, such as steel, quartz, borosilicate, soda lime, glass-lined steel, carbon fiber, and carbon nanotube liners. As shown in Figure 3A, the internal channel of the tubular body 13 is formed with a bottom taper 15, which means that the internal diameter of the internal channel progressively and continuously reduces in the downstream direction in at least a portion of tubular body 13. Such forms are well known in the art. The insert 10 is pushed into the tubular body 13 from an upstream end of the tubular body 13 in a downstream direction towards the bottom taper 15. The insert 10 adopts a dished configuration above the bottom taper 15. A sealing engagement is formed between the underside of the insert 10 and the progressively reducing walls of the taper 15.

[0094] In the second embodiment of Figure 3B, the internal channel of tubular body 13 is formed with an internal reduction in diameter which creates a restriction at an intermediate or mid-point of tubular body 13 and provides an internal seat 17 for the insert 10. The insert 10 is pushed into the tubular body 13 from an upstream end of the tubular body 13 in a downstream direction towards internal seat 17. The insert 10 again adopts a dished configuration above internal seat 17. A sealing engagement is formed between the underside of the insert 10 and internal seat 17.

[0095] In the third embodiment of Figure 3C, the tubular body 13 has a form which is the same as that of Figure 3A. In addition to the insert 10, there are two further inserts 10, arranged so that the three inserts 10 are spaced apart by two spacers 19. The spacers 19 are in the form of glass tubular members having an outside diameter which is less than the inside diameter of the internal channel 12 of the tubular body 13. To form the sample inlet liner 20, a first insert 10 is pushed into the tubular body 13 from an upstream end of the tubular body 13 in a downstream direction towards the bottom taper 15. The first insert 10 adopts a dished configuration above the bottom taper 15. A sealing engagement is formed between the underside of the first insert 10 and the progressively reducing walls of the taper 15. A first spacer 19 is then inserted into the tubular body 13 from an upstream end of the tubular body 13 in a downstream directiontowards the first insert 10. First spacer 19 creates an upper annular surface and a lower annular surface, with the lower annular surface bearing against first insert 10, and the upper annular surface forming a seat for any subsequent inserts. In this embodiment, the upper annular surface forms an annular seat for second insert 10. Second insert 10 is now pushed into the tubular body 13 from an upstream end of the tubular body 13 in a downstream direction towards the upper annular surface of the first spacer 19. The second insert 10 adopts a dished configuration above the first spacer 19. A sealing engagement is formed between the underside of the second insert 10 and the upper annular surface of first spacer 19. A second spacer 19 is then inserted into the tubular body 13 from an upstream end of the tubular body 13 in a downstream direction towards the second insert 10. Second spacer 19 creates an upper annular surface and a lower annular surface, with the lower annular surface bearing against second insert 10, and the upper annular surface forming an annular seat for third insert 10. Third insert 10 is now pushed into the tubular body 13 from an upstream end of the tubular body 13 in a downstream direction towards the upper annular surface of the second spacer 19. The third insert 10 adopts a dished configuration above the second spacer 19. A sealing engagement is formed between the underside of the third insert 10 and the upper annular surface of second spacer 19.

[0096] In the fourth embodiment of Figure 3D, the tubular body 13 has a form which is the same as that of Figure 3B. As per Figure 3B, a first insert 10 sits on the seat 17, above which is a spacer 19 in the form of a glass tubular member. Above the spacer 19 sits a second insert 10. This form of liner has particular application for large-volume injection (LVI).

[0097] In the fifth embodiment of Figure 3E, the tubular body 13 has a form which is the same as that of Figure 3A. A first insert 10 sits atop the bottom taper 15. A second insert 10 is spaced above the first insert 10 by a spacer in the form of glass beads 21 . The glass beads 21 are used to make a longer flow path through the liner. Alternatives for the glass beads include: irregular glass or quartz materials (crushed), silica beads, ceramic beads, silica partials (spherical or irregular) diatomaceous earth or chromasorb, polymeric packing materials or GC column phases materials on a support medium.

[0098] In the sixth embodiment of Figure 3F, the tubular body has a form which is the same as that of Figure 3B. As per Figure 3B, a first insert 10 sits on the seat 17, above which is a spacer in the form of glass beads 21 . The alternatives for the glass beads set out above in connection with Figure 3E may also have application for the configuration illustrated in Figure 3F.

[0099] In the seventh embodiment of Figure 3G, the tubular body 13 has a form which is the same as that of Figure 3B. A plurality of inserts 10 are stacked one atop the other above seat 17, without the use of a distinct spacer.

[0100] Reference is made to Figure 11 , which provides a further embodiment of a liner 20. Tubular body 13 has a form which is the same as that of Figure 3A save for the inclusion of a pair of opposed dimples 23, each dimple 23 extending inwardly into internal channel 12 and disposed adjacent an upper (or upstream) surface of insert 10. In the present embodiment, dimples 23 are formed by heating a portion of tubular body 13, such as at generally opposed locations of tubular body 13, and then pressing or pushing the heated portion of tubular body 13 inwardly (by a pin or other implement) at the opposed locations to form the inwardly projecting dimples 23. Whilst dimples 23 can be formed prior to insertion of insert 10 into tubular body 13, it is preferred that dimples 23 are formed after insert 10 is inserted and suitably positioned in sealing engagement with the progressively reducing walls of the taper 15.

[0101] Dimples 23 act as retention formation configured to substantially prevent dislodgement of insert 10 from its sealing engagement with internal channel 12 when liner 20 is in use. During use, insert 10 can be subjected to sudden or large pressure variations (for example, from pressure release and / or backpressure through the internal channel) that could cause dislodgement of insert 10 if not suitably retained. Whilst it can be application specific, preferred retention formation should be able to substantially prevent dislodgement of insert 10 when subjected to up to about 20 psi.

[0102] Whilst the retention formation depicted in Figure 11 relates to a pair of opposed dimples 23, a person skilled in the art will appreciate that different forms of retention formation can be used to substantially prevent the dislodgement of insert 10 during a sudden or large pressure event (e.g. through use of additional dimples, an annular ring, etc). It will also be appreciated that the use of retention formations can be provided atalternative locations of the tubular body, so long as they are generally provided in close proximity to insert 10.

[0103] Once the liner has been created in the preferred configuration, the whole liner, including the tubular body, the insert(s) and the spacer(s) is chemically deactivated in the known manner, such as by a silanization process. However, it will be appreciated that in other embodiments each of the tubular body, the insert(s) and the spacer(s) can be chemically deactivated individually before formation of the sample inlet liner.

[0104] It will be understood that one of the advantages of the present invention is in the use of a material having consistent characteristics. The preformed fibre sheet material insert is formed of a uniform material having a substantially consistent bulk density, pore size and thickness. Provision of such an insert provides the benefit of repeatability to an extent that was not realisable with a random filamentary mass formed of glass wool. This allows for more accurate and consistent chromatographic results. Further, the preformed fibre sheet material insert can have a longer service life than glass wool, which is more fragile and prone to damage through repeat use. Furthermore, this material is easy to work with and apply to the glass liner.

[0105] One of the roles of the insert in the tubular body of the liner is to retain a quantity of a sample injected into the liner and thereby provide a diffusion path for the retained quantity of the injected sample. Suitably, the insert offers an array of interstices, channels, and the like that is sufficient to provide a tortuous path for a sample injected into the sample inlet liner. The insert thereby assists with the vaporisation of the liquid sample, as well as promoting better mixing between the sample and the carrier gas.Results

[0106] Tests were conducted to compare results of sample inlet liners having a preformed fibre sheet material insert in accordance with the present disclosure and conventional glass or quartz wool liners.

[0107] For the tests with results shown in Figures 4-8, the preformed fiber sheet material was a microfiber sheet of borosilicate glass, with a pore size of 2.7 pm and a thickness of 675 pm (in accordance with GF / D grade from table 1 above).

[0108] An 8270 test and endrin / DDT breakdown test were conducted with sample inlet liners having a bottom taper and either a glass microfiber sheet or quartz wool. As shown in Figures 4 and 5, both quartz wool and glass microfiber sheet liners passed the minimum relative response factor (RRF) requirement for all eleven tested compounds with the 8270 test. As shown in Figure 6, both quartz wool and glass microfiber sheet liners passed the endrin / DDT breakdown test within 3% breakdown limit.

[0109] Repeatability tests were conducted with sample inlet liners having a taper approximately midway along the length of the tubular body and either a glass microfiber sheet or quartz wool (using a wet dipped deactivated glass tubular body). The repeatability of the glass microfiber sheet and quartz wool liners was tested with repeated fifteen injections of C14, C15, and C16 straight chained hydrocarbons in Hexane. The results in Figure 7 show that both glass microfiber sheet and quartz wool liners passed repeatability criteria with relative standard deviation (RSD) % less than 2%.

[0110] A chromatography analysis was conducted to analyse pesticides in various soil samples. Liners having preformed fibre sheet material and liners having wool were evaluated for analysing pesticides Methaacrifos, Ethoprofos, Chlordimeform, and Simazine in soil samples. For the sheet liners, both a glass sheet liner and quartz sheet liner (of similar properties to the glass sheet liner were assessed. The quartz sheet liner is a high-purity quartz (SiO2) microfiber filter of QM-A grade (as per table 2 above), having a pore size of 2.2 pm.

[0111] As shown in Figure 8, for the 1stinjection no difference was found among the three liners (glass sheet liner, quartz sheet liner, and wool liner) in terms of level of contamination. However, by the 50thinjection there was a clear difference of contamination level for the three liners, with the contamination level of the wool liner significantly higher than that of glass and quartz sheet liners. This is evident in Figure 8 from the false peaks in the wool liner results. This can be attributed to the significant barrier provided by the glass and quartz sheet liners relative to that of the wool liner.

[0112] The intra-liner repeatability of peak area of each pesticide for 50 injections are shown in Figures 9 and 10. All liners produced an average RSD% < 5% for the 4 pesticides analysis in the soil samples. The average RSD% of three wool liners are between 2.06% and 3.49%. While the glass and quartz sheet liners generally demonstrated a higher value than that of the wool liners, the value is still within the range of ±1% of that using wool liners.

[0113] In a further test, soil extract was used to compare the performance of quartz sheet liners in accordance with the disclosure and quartz wool liners. Both liners underwent repeated soil extract injections. This involved preparing a soil matrix mixed with acetone and hexane, which was then centrifuged, the supernatant decanted, and finally the mixture injected through the tubular body. After exposing each of the quartz liner and quartz wool to a set number of soil extract injections, the quartz liner and quartz wool were tested using the 8270 semi-volatile organic compound mix. Liner lifespan was assessed by the number of soil injections each form of liner was subjected to before failing internal production limits for the 8270 test (0.09 being the minimum relative response factor which is the peak area of 2,4-DNP divided by the peak area of the internal standard tetradecane. This is a minimum area required to assess activity and is normalized along with all test results to the area of the internal standard). As shown in Figure 12, the quartz sheet liners lasted about three times longer than quartz wool liners (400 vs 130 injections).

[0114] In a further test, an avocado acetonitrile extract was spiked with 3ppm of a pesticides mix (including alkanes used for internal standards testing). The quartz liner (the same quartz sheet liner as the previous test), a quartz wool liner and a glass frit liner were compared. Each liner was subjected to 297 injections of the extract and analysed. Figure 13 shows three chromatograms. The bottom chromatogram is of the pesticide mix, showing 10ppm of alkanes C12, C14, and C16, and 3ppm of the pesticides methacrifos, ethoprofos, chlordimeform, and simazine. The middle chromatogram is of the avocado acetonitrile extract (avocado and 1% acetic acid and acetonitrile solvent matrix). Notably, the top chromatogram is the results obtained from the analysis using the quartz sheet liner of the 10ppm alkanes C12, C14, and C16, and 3ppm in the pesticides methacrifos, ethoprofos, chlordimeform, and simazine.

[0115] The positive results from this test are further highlighted in Figure 14, which provides peak area trends for each of the quartz sheet liner, wool liner and glass frit liner. It will be understood that increased contamination through increased injections can interfere with the results causing a situation in which peak areas of pesticides diminish due to increased activity but increase due to interfering contamination peaks. Thus, Figure 14 demonstrates superior results when using the quartz sheet liner due to the greater consistency of the peak areas for a given pesticide, as compared to the results observed from use of the wool liner and glass frit liner.

[0116] The positive results from this test are further highlighted in Figure 15, which provides chromatograms for each of the quartz sheet liner, wool liner and glass frit liner. For the quartz sheet liner, there was minimal variation of peak area and retention time as the injection number increased. For the wool liner and the glass frit liner, the peak area decreased and retention time shifted as the injection number increased.

[0117] The positive results from this test are further highlighted in Figure 16, which provides a table validating the analytical method for pesticides in the avocado extract. Pesticides in food matrices can be sensitive to inlet conditions. Calibration linearity was demonstrated for three pesticides, ranging from 1 .25 to 40 ng / mL, using the quartz sheet liners. The LOD (Limit of Detection) and LOQ (Limit of Quantification) for the three pesticides are listed in the Table. It will be appreciated that quartz sheet liner demonstrated lower LOD and LOQ than the quartz wool liner.

[0118] In a further test, three alkanes (C14, C15, C16) were injected with split quartz sheet liners and split quartz wool liners. These liners were of the mid-taper kind, i.e. similar to that shown in Figures 3B. Results for this test are shown in Figure 17, in particular the peak area, peak height and the height to area ratio. The higher height-to- area ratio normally indicates a sharp peak, typically suggesting good separation. It will appreciated that the quartz sheet liners showed better peak shape (higher height / area ratio) than wool liners with the same geometry.

[0119] In a further test, different liner geometries were tested using the aforementioned quartz sheet insert to test batch to batch variability. In this test, a liner geometry produced by manufacturer Shimadzu is of a generally smaller dimension (i.e. narrower internal diameter) than the liners previously tested (produced by manufacturer Agilent).A grob test mix (with alkanes) was analysed to test peak area repeatability. As shown in Figures 18A-18C, both alkane and grob test mix passed the 1% criteria.

[0120] The above set of results demonstrate that using glass and quartz sheet inserts in the sample inlet liners met the quality and repeatability requirements for gas chromatography analysis, and in many respects provided comparable results to conventional wool liners. However, significantly, the sample inlet liners having glass or quartz sheet inserts showed improved performance over extended use given that they showed significantly lower contamination levels, and therefore did not produce false peaks as early in their use life as the wool liners.

[0121] As previously mentioned, from a manufacturability perspective, the preformed fibre sheet insert is formed of a uniform material having a substantially consistent bulk density, pore size and thickness. This provides the benefit of repeatability to an extent that was not realisable with a random filamentary mass formed of wool. This allows for more accurate and consistent chromatographic results. Further, the preformed fibre sheet insert can have a longer service life than wool, which is more fragile and prone to damage through repeat use. This is a particular drawback of wool liner applications, as any damage to the wool will result in exposed surfaces that are not chemically deactivated, and hence can adsorb and / or otherwise react with the sample and thereby create errors in the analysis.

[0122] The foregoing describes some embodiments of the present invention and modifications may be made thereto without departing from the present invention. For example, various different arrangements of inserts and spacers can be made.

[0123] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

CLAIMS1 . A method of forming a sample inlet liner for gas chromatography, the method including: providing a tubular body defining an internal channel; forming an insert from preformed fibre sheet material; and inserting the insert into the internal channel of the tubular body such that the insert extends across the internal channel; wherein the shape and size of the insert is commensurate with or oversized relative to the internal channel of the tubular body.

2. The method of claim 1 , wherein the material used to form the insert is one of a preformed glass fibre sheet material or a preformed quartz fibre sheet material.

3. The method of claim 2, wherein the preformed glass fibre sheet material or the preformed quartz fibre sheet material is a preformed glass fibre mat or preformed quartz fibre mat, respectively.

4. The method of any one of the preceding claims, wherein the insert includes an array of interstices, channels, and / or the like that is configured to provide a tortuous path for a sample injected into the sample inlet liner.

5. The method of any one of the preceding claims, wherein the insert is configured to provide a desired restriction of flow through the internal channel but mitigate against an undesired level of backpressure in the internal channel.

6. The method of any one of claims 2 to 5, wherein the sheet material has a nominal thickness in the range of about 100 pm and about 2000 pm.

7. The method of claim 6, wherein the sheet material has a nominal thickness in the range of about 250 pm and about 700 pm.

8. The method of any one of claims 2 to 7, wherein the sheet material is consistent or uniform in bulk density.

9. The method of claim 8, wherein the bulk density of the sheet material ranges from about 20 g / m2to about 500 g / m2.

10. The method of any one of claims 2 to 9, wherein the sheet material is consistent or uniform in pore size.11 . The method of claim 10, wherein the pore size of the sheet material ranges from between about 0.1 pm and about 200 pm.

12. The method of claim 11 , wherein the pore size of the sheet material is between about 0.4 pm and about 50 pm.

13. The method of any one of claims 2 to 12, wherein the preformed fibre sheet material insert is formed of a uniform material having a substantially consistent bulk density, pore size and thickness.

14. The method of any one of the preceding claims, wherein the insert has a diameter between about 1 and about 2 times a diameter of the internal channel before insertion into the internal channel.

15. The method of any one of the preceding claims, wherein said inserting the insert into the internal channel includes the inserting the insert into the tubular body in a manner which creates a dished or concave shape.

16. The method of claim 15, wherein an outer periphery of an undersurface of the insert makes contact with a surface of the internal channel to thereby create a sealing engagement, said sealing engagement between the insert and the internal channel of the tubular body being completely due to or substantially due to the oversized insert.

17. The method of any one of the preceding claims, wherein the tubular body includes an obstruction, restriction or tapering of the internal channel, and wherein the insert is disposed such as to lie against the obstruction, restriction or tapering of the internal channel.

18. The method of any one of claims 2 to 17, wherein the method further includes deactivating surface(s) of the preformed fibre sheet material insert and thetubular body after inserting the insert into the internal channel of the tubular body, thereby deactivating said surfaces at the same time.

19. The method of any one of the preceding claims, wherein the tubular body includes retention formation configured to substantially prevent dislodgement of the insert from the internal channel or from a predetermined position within the internal channel, when the liner is in use.

20. The method of claim 19, wherein the retention formation includes an obstruction, restriction or tapering of the internal channel disposed upstream of the insert.21 . The method of claim 20, wherein the retention formation is in the form of one or more dimples extending into the internal channel.

22. The method of any one of claims 19 to 21 , wherein the method further includes forming the retention formation of the tubular body, said forming the retention formation including heating the tubular body at one or more locations, and pushing the tubular body inwardly at the one or more locations to form the one or more dimples extending into the internal channel.

23. The method of claim 22, wherein said retention formation is formed after inserting the insert into the internal channel.

24. A sample inlet liner for gas chromatography, the liner including: a tubular body defining an internal channel; and a preformed insert formed from preformed glass or quartz fibre sheet material, the preformed insert being disposed within the tubular body such that the insert extends across the internal channel and has a size and shape which is commensurate with or oversized relative to the dimensions of the internal channel.

25. The sample inlet liner of claim 24, wherein the preformed glass fibre sheet material or the preformed quartz fibre sheet material is a preformed glass fibre mat or preformed quartz fibre mat, respectively.

26. The sample inlet liner of claim 24 or 25, wherein the insert includes an array of interstices, channels, and / or the like that is configured to provide a tortuous path for a sample injected into the sample inlet liner.

27. The sample inlet liner of any one claims 24 to 26, wherein the insert is configured to provide a desired restriction of flow through the internal channel but mitigate against an undesired level of backpressure in the internal channel.

28. The sample inlet liner of any one of claims 24 to 27, wherein the sheet material has a nominal thickness in the range of about 100 pm and about 2000 pm.

29. The sample inlet liner of claim 28, wherein the sheet material has a nominal thickness in the range of about 250 pm and about 700 pm.

30. The sample inlet liner of any one of claims 24 to 29, wherein the sheet material is consistent or uniform in bulk density.31 . The sample inlet liner of claim 30, wherein the bulk density of the sheet material ranges from about 20 g / m2to about 500 g / m2.

32. The sample inlet liner of any one of claims 24 to 31 , wherein the sheet material is consistent or uniform in pore size.

33. The sample inlet liner of claim 32, wherein the pore size of the sheet material ranges from between about 0.1 pm and about 200 pm.

34. The sample inlet liner of claim 33, wherein the pore size of the sheet material is between about 0.4 pm and about 50 pm.

35. The sample inlet liner of any one of claims 24 to 34, wherein the preformed fibre sheet material insert is formed of a uniform material having a substantially consistent bulk density, pore size and thickness.

36. The sample inlet liner of any one of claims 24 to 35, wherein the insert has a diameter between about 1 and about 2 times a diameter of the internal channel before insertion into the internal channel.

37. The sample inlet liner of any one of claims 24 to 36, wherein the insert is disposed in the internal channel in a dished or concave shape.

38. The sample inlet liner of claim 37, wherein an outer periphery of an undersurface of the insert makes contact with a surface of the internal channel to thereby create a sealing engagement, said sealing engagement between the insert and the internal channel of the tubular body being completely due to or substantially due to the oversized insert.

39. The sample inlet liner of any one of claims 24 to 38, wherein the tubular body includes an obstruction, restriction or tapering of the internal channel, and wherein the insert is disposed such as to lie against the obstruction, restriction or tapering of the internal channel.

40. The sample inlet liner of any one of claims 24 to 39, wherein the tubular body includes retention formation configured to substantially prevent dislodgement of the insert from the internal channel or from a predetermined position within the internal channel, when the liner is in use.41 . The sample inlet liner of claim 40, wherein the retention formation includes an obstruction, restriction or tapering of the internal channel disposed upstream of the insert.

42. The sample inlet liner of claim 41 , wherein the retention formation is in the form of one or more dimples extending into the internal channel.

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