A thermal modulator column holder

Abstract

The invention relates to a column holder for a thermal modulator comprising: a body; a modulator zone at a first end of the body that is aligned with the hot and cold jets of the thermal modulator; a

Description

FIELD OF INVENTION

[0001] The present invention relates to a column holder for a thermal modulator used in a comprehensive two-dimensional gas chromatography system. BACKGROUND

[0002] Traditional one dimensional gas chromatography (GC) is a well-established technique for separating out and analysing the various components of a compound. However, standard one-dimensional GC is limited in its ability to separate complex compounds with high numbers of differing components. The introduction of comprehensive two-dimensional gas chromatography (GC x GC), which is a multidimensional gas chromatography technique, has significantly improved the characterisation of complex mixtures of volatile compounds. GC x GC utilizes two different gas chromatography columns, arranged sequentially, with each having a different stationary phase. Typically, the first-dimension column is a conventional GC capillary column, having a non-polar stationary phase. The first dimension column therefore separates components largely based on their vapour pressure. The second-dimension column is smaller in diameter, and typically shorter than the first-dimension column. As a result, the separations achieved by the second-dimension column are significantly faster than the first dimension column.

[0003] A first separation is performed on the first dimension column. The separated effluent from the first dimension column is then passed through the second dimension column for further separation. Traditional multidimensional gas chromatography (MDGC) utilises a "heat-cutting" technique, in which only certain parts of the eluate from the first dimension are transferred to the second dimension, which reduces the sensitivity of the technique. GC x GC improves on this method by introducing a modulator between the first and second dimension stages. The modulator quickly traps, then injects the effluent from the first dimension column onto the second dimension, allowing the entire effluent from the first dimension to be separated in the second dimension. Thermal modulation is a common technique in GC x GC experiments.

[0004] A thermal modulator utilises a cooled gas stream to create a cooling jet. The cooling jet may be cooled via a refrigeration unit or using cryogens such as liquid nitrogen for colder temperatures. The cooling jet thermally traps all the components of the elute from the first dimension in a modulator stage of the capillary column. The thermally trapped components are then released by a hot stream pulse, which re-mobilises the components and releases them into the carrier gas stream. The mobilised components are subsequently carried into the second column. The thermally immobilised components are rapidly released by the hot pulse over a much shorter period then the initial immobilisation stage. In this way the analyte is focussed and released to the second dimension column with a much smaller bandwidth. The hot pulse is referred to as an injection, which initiates the analyte into the second dimension column.

[0005] One known thermal modulation system is a two stage loop modulator, also referred to as a delay loop modulator. A two-stage loop modulator directs hot and cold jets to a double looped capillary tubing. The cold jet creates two cold spots on adjacent looped sections of the capillary. The section of capillary tube between the cold spots is referred to as the delay loop. A delay loop is typically 60-100 cm long. Material entrapped at the cold spots is released by switching on the hot jet. Material on the first cold spot is released towards the second cold spot while the material on the second cold spot is released to the second dimension column. Efficient entrapment and release of the analytes relies on correct and continued alignment of the cold spots with the hot and cold jets.

[0006] The second modulation stage of a two stage loop modulator traps any analytes that pass through the first modulation point while the hot jet is activated in a process referred to as breakthrough. Those analytes passing through during hot jet activation are effectively unmodulated as they weren't initially trapped by the cold jet at the first modulator stage. The second modulator stage therefore provides a second mechanism for trapping and modulating breakthrough analytes.

[0007] The time taken for analytes to travel between the modulator stages under a specific set of method parameters is determined by the length of the delay loop (i.e. the distance along the capillary column between the two modulator stages). The length of capillary column should be optimised in length to ensure the time taken for the analytes to travel between the modulation points is not excessively long or too short. A nonoptimised delay loop length can impact the effective temperature of modulation at the second modulation stage, which in turn can affect the efficiency of the modulation.

[0008] The column flow, oven temperature, column diameter and modulation period will all impact the time taken for the analytes to travel along the delay loop, so it means that the column length of the delay loop may need to change as the method parameters change. Once an optimised delay loop length is determined, ensuring that the delay loop length doesn't vary during use and being able to repeat that length for future analytical configurations is crucial for reproducible results. Also, due to the requirement to periodically replace columns, it is desirable to be able to confidently re-configure the system with the same delay loop length on a new section of column.

[0009] The capillary tube of the thermal modulator is held within a column holder. An example of a typical column holder of the prior art is shown in Figure 1. The column holder 3 comprises a metal plate 5 having bent side edges 7 with open ends. The capillary tube 9 is looped within the holder, with two loops extending from one end of the holder 3. The apex of each loop defines a modulator stage and the loops are arranged such that the modulator stages are located within the hot and cold jet streams. A length of the capillary tube is formed into additional loops within the holder 3 and the returning spring force of the capillary tube against the bent edges 7 of the plate 5 holds the capillary tube loosely within the column holder. Looping of the capillary tube is done manually and by eye, and as such it is difficult to form the loops such that the modulator stages accurately extend from the column holder 3 to the correct position. It is also difficult to achieve an accurate distance between the modulator stages to define the length of the delay loop, or to consistently reproduce the looped configuration each time the capillary tube is replaced to repeatedly create a constant delay loop. Heating and cooling of the modulator stages causes movement of the capillary tube both horizontally towards and away from the end of the holder 3 and vertically within the bent edges. This moves the modulator stages out of position resulting in sub-optimal modulation and / or varies the length of the delay loop and the position of the modulator stages along the capillary tube leading to inconsistent results.

[00010] It is therefore desirable to provide an improved column holder for a thermal modulator, which addresses the above-described problems and / or which offers improvements generally. SUMMARY

[00011] According to the present invention there is provided a column holder for a thermal modulator for comprehensive two-dimensional gas chromatography as described in the accompanying claims.

[00012] In an aspect of the invention there is provided a column holder for a thermal modulator, the thermal modulator having hot and cold jets. The column holder comprises a body configured to be mounted to a thermal modulator; a modulator zone located at a first end of the body that in use is aligned with the hot and cold jets of the thermal modulator; and a plurality of winding elements provided on the body about which a capillary tube may be wound. The winding elements are arranged in an array defining one or more winding pathways extending through the modulator zone along which the capillary tube is wound, the winding elements being configured such that when a capillary tube is wound along the one or more winding pathways the winding elements retain the capillary tube on the column holder. The capillary tube may be retained by frictional engagement with the winding elements and / or within grooves or channels on the winding elements and / or may include clips or other retaining elements to hold the capillary tube.

[00013] A winding pathway configuration is achieved by winding the capillary tube around a selected number of winding elements in a given sequence. The array of winding elements is fixed and the winding pathways are predefined and reproducible, such that each time a capillary tube is wound along a given winding pathway its wound length and the location of the sections that extend across the modulator zone will be the same.

[00014] The plurality of winding elements may comprise a plurality of projections upstanding from the body.

[00015] The body may comprise a base and the plurality of projections are upstanding from the base. The base may be a planar substrate and the projections may extend substantially perpendicular to the base.

[00016] The plurality of projections may be integrally formed with the base. The projections may be formed for example by machining the body, or the body and projections may be formed for example by additive manufacture such as 3D printing.

[00017] The array defines one or more winding pathways configured such that when wound along said one or more winding pathways the capillary tube extends across the modular zone twice to create two modulator stages along the capillary tube. The modulator stages are the sections of the capillary tube within the modulator zone that are intersected by the hot and cold jets in use.

[00018] The modulator zone may be a region defined by an opening or recess in the body section and / or a region defined at a fixed location spaced from the end of the body section, being the region that intersects the hot and cold jets when the column holder is mounted to the thermal modulator.

[00019] The modulator zone is arranged such that in use it coincides with the hot and cold jets of the thermal modulator and such that the modulator stages of the capillary tube located in the modulator zone are exposed to and located within the hot and cold jets. The ability to hold the capillary tube on a winding pathway accurately and repeatably locates the modulator stages at the same position relative to the column holder body and relative to the hot and cold jets when mounted to the thermal modulator. The term 'mounted' to the thermal modulator is not intended to be limiting and means any method of securing the column holder to the thermal modulator.

[00020] The array of winding elements is configured to define one or more winding pathways comprising first and second adjacent loops wherein the first loop extends across the modulator zone.

[00021] The base may comprise first and second upstanding side walls located at respective first and second sides of the base, and the first and second side walls each include an end section located at the first end of the base adjacent the modulator zone, the end sections curving inwardly towards each other and towards the modulator zone. The free ends of the curved end sections are spaced from each other either side of the modulator zone, which is a gap defined between the end sections.

[00022] The side walls may be arranged to laterally restrain the capillary tube and cooperate with the winding elements to hold the capillary tube in the winding formation. The body has a length extending between its first and second ends and lateral direction is perpendicular to the length.

[00023] A third upstanding end wall may be located at a second end of the body opposite the first end at which the modulator zone is located, the third wall being arranged to restrain the capillary tube and cooperate with the winding elements to hold the capillary tube in the winding formation.

[00024] An opening may be defined in one or more of the upstanding walls and / or between one or more of the side walls and the end wall, through which the capillary tube enters and / or exits the column holder.

[00025] The side walls may include concave guide channels extending lengthwise along their inner surfaces arranged to receive and guide the capillary tube.

[00026] The radius of curvature of the end sections may correspond to the radius of the first loop and is concentric therewith. The curved end sections are aligned along the first loop to define curved guides for the capillary tube.

[00027] The plurality of winding elements may be arcuate in shape, having a radius of curvature corresponding to the radius of their respective winding loop.

[00028] The winding elements have curved inner and outer walls and a guide channel is formed along at least one of the inner and outer walls.

[00029] In another aspect there is provided a thermal modulator for gas chromatography, the thermal modulator comprising a hot gas jet operative to expel a heated gas stream; a cold gas jet operative to expel a cold gas stream; and a column holder according to any preceding claim, wherein the column holder is arranged such that the modulator zone is aligned with the hot and cold jets such the hot gas stream and the cold gas stream pass through the modulator zone.

[00030] The thermal modulator may comprise a capillary tube wound around the winding elements along a winding pathway such that the capillary tube extends across the modulator zone twice, the sections of the capillary tube extending across the modulator zone being arranged to intersect the hot and cold gas streams. The sections of the capillary tube intersecting the hot and cold gas streams define modulator stages and the length of capillary tube between the modulator stages defines a delay loop.

[00031] In another aspect there is provided a method of mounting a capillary tube within a thermal modulator having hot and cold jets, the method comprising providing a column holder according to any preceding claim; winding the capillary tube around the plurality of winding elements along a winding pathway such that the capillary tube extends across the modulator zone twice; and mounting the column holder to the thermal modulator such that the sections of the capillary tube extending across the modulator zone are aligned within the hot and cold jets such that they are intersected by the hot and cold gas streams respectively, wherein the two sections of the capillary tube aligned with the hot and cold jet define two modulator stages.

[00032] The column holder may include mounting means for mounting the column holder to a thermal modulator.

[00033] One or more of the winding pathways may be fully or partially formed as a figure of eight.

[00034] The modulator zone may be a region defined by an opening or recess in the body section and / or a region defined at a location spaced from the end of the body section.

[00035] The winding projections may be spaced from the one of more walls and one or more guide channels are defined between one or more of the projections and the one or more or more walls for guiding the capillary tube along the winding pathway.

[00036] The curved end sections of the side walls form curved guide channels that form the capillary tube into an arc of fixed radius as it extends across the modulator zone.

[00037] The column holder my include mounting means for releasably mounting the column holder to a corresponding support element of the thermal modulator.

[00038] The body section may comprise one or more walls arranged at a periphery of the body section, the one or more walls cooperating with the winding projections to form the one or more winding pathways. The one or walls also act to restrain the capillary tube and prevent outward expansion of the capillary tube within the column holder.

[00039] The array of projections may be arranged to create a winding pathway comprising one or more loops. One winding pathway may be formed as a figure of eight. A winding pathway is a fixed path achieved when the capillary tube is wound around the winding elements in a specific sequence.

[00040] The modulator zone is a zone located relative to the body of the column holder that aligns with the hot and cold jets when mounted to the thermal modulator. BRIEF DESCRIPTION OF THE DRAWINGS

[00041] The present invention will now be described by way of example only with reference to the following illustrative figures in which: Figure 1 shows a column holder of the prior art; Figure 2 shows a thermal modulator with a column holder according to an embodiment of the disclosure; Figure 3 shows a view from below of a thermal modulator with a column holder according to an embodiment of the disclosure ; Figure 4 shows a view of the lower surface of a column holder according to an embodiment of the disclosure; Figures 5a-5c is a sequential illustration of a capillary tube being wound along a winding pathway according to an embodiment of the disclosure; Figure 6 shows the lower surface of a column holder according to an embodiment of the disclosure with an enlarged view of the modulator zone; Figure 7 shows a view of the upper surface of a column holder according to an embodiment of the disclosure; and Figure 8 shows a view from below of a thermal modulator without a column holder mounted, according to an embodiment of the disclosure. DESCRIPTION OF EMBODIMENTS

[00042] Referring to Figure 2, there is provided a delay loop thermal modulator 1 for use with a two- dimensional gas chromatograph. The thermal modulator 1 comprises a cold jet assembly 4 having a cold jet nozzle 6 that directs a cold gas stream along a first flow path A. A hot jet assembly 8 includes a housing 10 including a heating element and a hot jet nozzle 12 that directs a hot gas stream along a second flow path B. The hot jet assembly 8 includes a valve arrangement operable to pulse the hot gas stream. The direction of the first flow path A is substantially vertically downwards and the direction of the second flow path B is substantially horizontal, such that the first and second flow paths A,B are orthogonally arranged.

[00043] A carriage 14 is mounted to the housing 10 of the hot jet assembly 8 and is also connected to the cold jet assembly 4. The carriage 14 includes a first plate section 16 that is arranged substantially horizontally and a second plate section 18 that is angled upwardly relative to the first plate section 14 and extends away from the hot jet assembly in the direction of the second flow path B. The second plate section 18 includes a plurality of mounting channels 20 formed on a lower surface 22, as will be described in further detail. The second plate section 18 joins the first plate section 14 at a proximal end 26 and has an opposing distal end 24.

[00044] The cold jet nozzle 6 has a cold jet nozzle tip 28. The hot jet nozzle 12 has a hot jet nozzle tip 30. The cold jet nozzle tip 28 is spaced above the hot jet nozzle tip 30 and above the second flow path B. The hot jet nozzle tip 30 is spaced below the cold jet nozzle tip 28 and is spaced horizontally from the first flow path A. A modulation zone 32 is defined at the point the first cold jet flow path A and second hot jet flow path B intersect.

[00045] Referring to Figure 3, the second plate section 16 is angled downwardly from its distal end towards the modulation zone 32. A column holder 34 is mounted to the lower surface 22 of the carriage 14. The column holder 34 comprises a body 36 having a base 38 with a lower surface 40 that faces downward when mounted to the carriage in use and an upper surface 42 that faces the carriage. The column holder 34 includes a first end 46 that is uppermost and a second end 48 that is lowermost mounted to the carriage 14. The column holder 34 is angled downwardly at the same angle as the carriage and the second end 48 is arranged proximate the modulator zone 32.

[00046] As shown in Figure 4, the base 38 of the column holder 34 is planar and substantially rectangular with a width and a length, a first side 50 and second side 52. The second end 46 of the column holder 34 is curved, having a diameter DI corresponding and substantially equal to the width. Upstanding side walls 54,56 are arranged at the first and second sides 50,52 respectively. Upstanding end wall 58 is arranged at the first end 46. Side wall 54 is spaced from the end wall 58 defining a first opening 60. Side wall 56 is spaced from the end wall 58 defining a second opening 62. A first curved concave channel 64 is formed in and extends lengthwise along the inner surface 66 of the first side wall 54, parallel to the base 38. A second curved concave channel 68 is formed in and extends lengthwise along the inner surface 71 of the second side wall 56, parallel to the base 38. A third channel 72 extends lengthwise along the inner surface 74 of the end wall 58, parallel to the base 38.

[00047] The first side wall 54 has a curved end section 72 and the second side wall 56 has an inwardly curved end section 74. The end sections 72,74 are located at the second end 48 of the column holder 34 and curved inwardly towards each other at their distal ends. The curved end sections 72,74 function as curved guides for the capillary tube 77. An opening 70 is formed in the second end 48 of the column holder 34. The opening 70 defines a modulator gap 71 between the end section 72 of the first side wall 54 and the end section 74 of the second side wall 56. A cutaway section 76 is formed in the base 38 that extends the opening into the body 34

[00048] The thermal modulator 1 includes a length of capillary tube 77, also referred to as the modulator column. The capillary tube 77 is held and retained by the column holder 34. A plurality of projections 78a-f extend from the lower surface of the base 38, that is to say the surface of the base that is downwardly facing in use. The projections 78 form a plurality of winding elements upstanding from the base 38 about which the capillary tube 77 is wound within the holder 34. Each projection is integrally formed with the body 10, which may be formed for example by 3D printing. However, it will be appreciated that in other embodiments the projections may be separate components secured to the base. The projections 78 each comprise an elongate curved body having a height H, width W2, length L2, and inner wall and an outer wall. Curved concave channels 80,82 are formed along the inner and outer walls of the projections 78 respectively. The channels 80,82 are arranged parallel to the base 38 and correspond in cross sectional shape to the channels 64,68,72 of the side walls 54,56 and end wall 58.

[00049] The winding projections 78 are spaced inwardly from the side walls 54,56 and end wall 58. The projections 78 are arranged in a spaced array to define one or more winding pathways. In the embodiment of Figure 4, a first set of projections 78a-d are arranged in a substantially circular array to form a first circular winding loop 84 that forms a first part of a winding pathway. Projections 78a and 78c are arranged at diametrically opposed locations on the circular array. Projections 78b and 78d are similarly arranged at diametrically opposed locations. The projections 78a-d are circumferentially spaced from each around the circular array. The channels 82 formed on the outer walls of the projections 78a-d are vertically aligned and combine to form spaced sections of a circular channel that defines the first circular winding loop 84.

[00050] Projections 78e and 78f are arranged as part of a second circular array forming part of a second winding loop 86 that is adjacent the first winding loop. The radius of the second winding loop 86 corresponds to the radii of the curved end sections 72,74 of the side walls 54,56. The projections 78e and 78f are arranged such that they cooperate with the inner surfaces of the curved end sections 72,74 to form the second winding loop 86. The channels 82 on the outer surfaces of the projections 78e and 78f are vertically aligned with and correspond in shape to the channels 64,68 on the inner surfaces of the curved end sections 72,74, with the channels 80,64,68 combining to form spaced sections of a circular channel that defines the second winding loop 86. The first and second winding loops 84,86 are arranged adjacent each other and the array of projections define a plurality of winding pathways enabling a plurality of different winding configurations depending on how the capillary tube is wound around the projections 78.

[00051] Figures 5a-c illustrate one exemplary winding configuration. The winding process is shown in stages and the direction of winding is indicated by arrows. For illustrative purposes, only the section of the capillary tube involved in each winding stage is shown in each of the views, but it will be appreciated that the stages combine to form a complete winding configuration. In Figure 5a the capillary tube enters the column holder 34 via opening 62 in a direction parallel to the end wall 58 and runs in the channel 74. The capillary tube 77 is then wound around projection 78b and extends into and runs within the channel 64 of the side wall 54 to the projection 78d.

[00052] The capillary tube 77 is wound around projection 78d and then around projection 78e before extending within channel 68 to the second curved end section 74. The capillary tube 77 then exits the channel 68 and extends across the modulator gap 70. The end point of the capillary tube 77 shown in Figure 5a, midway across the modulator gap, represents the first modulator stage 88a. The capillary tube continues to the first end section 72 and extends into first channel 64, as shown in Figure 5b. The capillary tube 77 extends along the channel 64 and back to the projection 78b and is wound around projections 78a, 78c and 78f to complete the first winding loop 84 before returning to the first end section 72 and extending back across the modulator gap 70 in the opposing direction. The point at which the winding terminates across the modulator gap in Figure 5b represents the second modulator stage. The length of the winding illustrated in Figure 5b is the length of capillary tube between the first and second modulator stages 88a,8b and this length defines the delay loop 89.

[00053] As shown in Figure 5c, the capillary tube 77 is then wound around projections 78e, projection 78d completing the second winding loop 86 and then back to projection 78b before exiting the column holder via the opening 62. The frictional engagement of the capillary tube 77 with the projections 78 and the channels 66, 68 and 74 holds and retains the capillary tube 77 within the wound configuration and prevents movement of the capillary tube. In other exemplary configurations the capillary tube 77 may be wound around projections 78a and 78b and through the end sections 72,74 in a racetrack configuration.

[00054] In another exemplary configuration, the capillary tube 77 may be looped twice around the second winding loop 86 to create the two modulator stages 88a,88b but wound additional times around the first winding loop to extend the delay loop, as described in further detail below. The capillary tube 77 may also enter and exit via the first opening 60 or enter via one the first and second openings 60,62 and exit via the other of the first and second openings 60,62.

[00055] As shown in Figure 5, when the capillary tube 77 is wound around the first and second winding loops 84,86 it conforms to the circular form of the winding loops 84,86. The sections of the capillary tube 77 extending across the modulator gap 70 are therefore curved with a radius corresponding to the radius of the second winding loop 86 and likewise the radius of the end sections 72,74. Regardless of the winding configuration within the column holder 34, the capillary tube 77 must always run through and conform to the radius of the first and second end sections 72,74. The shape and radius of the sections of the capillary tube 77 spanning the modulator gap 70 is therefore constant for any winding formation. The apex of each section of capillary tube 77 spanning the modulator gap 70 defines a modulator stage 88. As can be seen from the enlarged view of Figure 6 the capillary tube 77 is looped such that is spans the modulator gap 70 twice. This creates two modulator stages 88a,88b - one on each loop. The location of the modulator stages 88a,88b relative to the body 36 of the column holder 34 is selected such that when the column holder 34 is mounted to the carriage 14 of the thermal modulator 1, the modulator stages 88a,88b, which are at the lowermost end of the column holder 34, are held at an optimised position within respect to the modulator zone 32. This positioning is selected to maximise the efficacy and efficiency of the heating and cooling jets in heating and cooling the modulator stages 88. The constant and repeatable radius of the capillary sections spanning the modulator gap 70 means that the modulator stages 88a,88b are always located at a fixed and constant position. Furthermore, the way the capillary tube 77 is held and retained within the column holder 34 is such the capillary tube 77 does not move in use, even as the temperature fluctuates, and hence the modulator stages 88a,88b are maintained at the optimum position within the modulator zone.

[00056] The channels 64,68,72 of the side walls 54,56 and end wall 58 are vertically aligned with the channels 80 of the projections 78 a-f. Vertical alignment means alignment in a direction perpendicular to the base 38. As the capillary tube 77 is wound around the projections 78a-f along a winding pathway, the capillary tube 77 is received within one or more of the channels 64,68,72 and the channels 80. The channels vertically restrain the capillary tube 77 and hold it in a fixed position relative to the base 38 along its length. Consequently, the vertical alignment of the modulator stages 88a,88b relative to the base 38, and hence its vertical position within the modulator zone 32, is fixed and repeatable, and is held constant during use.

[00057] The length of capillary tube 77 between the modulator stages 88a,88b defines the delay loop. The length of the delay loop depends on the winding configuration selected and the length of winding pathway along which the capillary tube 77 is wound before looping back across the modulator gap for the second time. The length of the delay loop may therefore be varied by varying the winding configuration, that is to say by selecting different winding pathways. However, because the position of the projections 78 are fixed, each particular winding configuration has a fixed and repeatable length. Therefore, for a given winding configuration the delay loop will be the same each time a capillary tube is wound in that configuration. The length of the winding, the length of the delay loop and the position of the modulator stages can therefore be selected and repeated by selecting a given winding configuration from the plurality of available winding configurations.

[00058] Referring to Figure 7, a plurality of mounting features 44 extend from the upper surface 42. The mounting features comprise a stem and a disc shaped head and are t-shaped in cross section, the head having a greater diameter than the stem. The mounting features are received within the mounting slots 20 of the carriage 14 and cooperate with the mounting slots 20 to secure the column holder 34 to the second plate section 16 in a parallel relationship. The mounting slots 20 are illustrated in Figure 8. The slots 20 are t-shaped, corresponding in shape and size to the mounting features and extend laterally into the lower surface of the carriage 22. An end portion of the slot extends longitudinally downwards to locate the column holder and prevent lateral release.

Claims

1. A column holder for a thermal modulator having hot and cold jets, the columnholder comprising:a body configured to be mounted to a thermal modulator;a modulator zone located at a first end of the body that in use is aligned with the hot and cold jets of the thermal modulator; anda plurality of winding elements provided on the body about which a capillary tube may be wound;wherein the winding elements are arranged in an array defining one or more winding pathways extending through the modulator zone along which the capillary tube is wound, the winding elements being configured such that when a capillary tube is wound along the one or more winding pathways the winding elements retain the capillary tube on the column holder2. A column holder according to claim 1, wherein the plurality of winding elements comprises a plurality of projections upstanding from the body.

3. A column holder according to claim 2 wherein the body comprises a base and the plurality of projections are upstanding from the base.

4. A column holder according to claim 3 wherein the plurality of projections are integrally formed with the base.

5. A column holder according to any preceding claim wherein the array defines one or more winding pathways configured such that when wound along said one or more winding pathways the capillary tube extends across the modular zone twice to create two modulator stages along the capillary tube.

6. A column holder according to claim 5 wherein the modulator zone is arranged such that in use it coincides with the hot and cold jets of the thermal modulator and themodulator stages of the capillary tube located in the modulator zone are exposed to the hot and cold jets.

7. A column holder according to claim 5 or 6 wherein the array is configured to define one or more winding pathways comprising first and second adjacent loops wherein the first loop extends across the modulator zone.

8. A column holder according to claim 7 wherein the base comprises first and second upstanding side walls located at respective first and second sides of the base, and the first and second side walls each include an end section located at the first end of the base adjacent the modulator zone, the end sections curving inwardly towards each other and towards the modulator zone.

9. A column holder according to claim 8 wherein the side walls are arranged to laterally restrain the capillary tube and cooperate with the winding elements to hold the capillary tube in the winding formation.

10. A column holder according to claim 9 further comprising a third upstanding wall located at a second end of the body opposite the first end, the third wall being arranged to restrain the capillary tube and cooperate with the winding elements to hold the capillary tube in the winding formation.

11. A column holder according to claim 9 or 10 wherein an opening is defined in one or more of the upstanding walls through which the capillary tube enters and / or exits the column holder.

12. A column holder according to any one of claims 8 to 11 wherein the side walls include guide channels arranged to receive and guide the capillary tube.

13. A column holder according to any one of claims 8 to 10 wherein the radius of curvature of the end sections corresponds to the radius of the first loop, and thecurved end sections are aligned along the first loop to define curved guides for the capillary tube.

14. A column holder according to any preceding claim wherein the plurality of winding elements are arcuate in shape.

15. A column holder according to claim 14 wherein the winding elements have curved inner and outer walls and a guide channel is formed along at least one of the inner and outer walls.

16. A thermal modulator for gas chromatography, the thermal modulator comprising: a hot gas jet operative to expel a heated gas stream;a cold gas jet operative to expel a cold gas stream; anda column holder according to any preceding claim, wherein the column holder is arranged such that the modulator zone is aligned with the hot and cold jets such the hot gas stream and the cold gas stream pass through the modulator zone.

17. A thermal modulator according to any preceding claim further comprising a capillary tube wound around the winding elements along a winding pathway such that the capillary tube extends across the modulator zone twice, the sections of the capillary tube extending across the modulator zone being arranged to intersect the hot and cold gas streams.

18. A method of mounting a capillary tube within a thermal modulator having hot and cold jets, the method comprising;providing a column holder according to any preceding claim;winding the capillary tube around the plurality of winding elements along a winding pathway such that the capillary tube extends across the modulator zone twice; andmounting the column holder to the thermal modulator such that the sections of the capillary tube extending across the modulator zone are aligned within the hotand cold jets, wherein the two sections of the capillary tube aligned with the hot and cold jet define two modulator stages.21

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