WO2016092280A1

WO2016092280A1 - Disposable device for capture of volatile compounds

Info

Publication number: WO2016092280A1
Application number: PCT/GB2015/053740
Authority: WO
Inventors: Frank Kvasnik
Original assignee: Sensam Limited
Priority date: 2014-12-08
Filing date: 2015-12-07
Publication date: 2016-06-16
Also published as: GB201421794D0; GB2533093B; GB2533093A

Abstract

A solid-phase micro extraction (SPME) device comprises a supporting substrate (10) in the form of a sheet of paper board, of cardboard or of plastics material having first and second major surfaces (11, 13) and first and second end regions. A layer (12) of gas barrier material is applied over the first end region of a least the first major surface (11). A volatile compound sorptive coating (14) is disposed on the gas barrier material on the first major surface (11). This may be on only a portion of the layer of gas barrier material (12), such as a central region of the first end region of the first major surface (11) where a depression or indentation (15) may be formed for this purpose. The second end region of the substrate (10) is dimensioned to serve as a handhold section (16) of the device. This SPME device may be used in combination with a breath sampler in the form of a hollow container, the SPME device being removably mounted to the breath sampler with the first end region of the SPME device protruding through a slot into the chamber of the sampler while the handhold section of said SPME device remains predominantly outside to facilitate rotation of said inner tubular part of the sampler from an open to a closed disposition. This SMPE device may also be used in combination with desorption apparatus having heating means for heating surface regions flanking the sorptive coating sufficient to release volatile substances therefrom.

Description

Disposable device for capture of volatile compounds

[0001] This invention relates to an improved solid-phase micro extraction (SPME) device for absorbing and/or adsorbing a volatile compound and subsequently releasing same for purposes of identification of the compound as well as to combination of same with a breath sampler and combination of same with apparatus for releasing (desorption of) said volatile compound from said device.

BACKGROUND

[0002] Solid-phase micro extraction is a technique originated in the 1990s which has now become established as a means for obtaining samples for analysis by gas chromatography. The technique is applicable for gas and liquid samples. It is simple and quick and does not require use of solvents. Furthermore, sampling can be carried out by non-scientists, and outside of laboratories. Special absorptive or adsorptive ("sorptive") materials are used to extract analytes of interest by capturing them in their matrices. These samples are stored and analysed at a later date without significant losses of the volatile materials. SPME is now the preferred technique for many circumstances where analysis of volatile compounds is required, such as in medical, environmental and industrial fields, to name a few.

[0003] The sorptive materials used to capture analytes of interest in their matrices are generally polymers and are generally used as a thin coating that needs supporting. Any substrate that supports such a coating must not itself generate any gases or vapours even when heated to elevated temperature that are typically needed to desorb captured analytes. Since SPME was invented for use in gas chromatography where instruments have input ports that accept needles of syringes, thin fibres, typically made from fused silica or some polymer, and typically of fibre diameter from about 50μηι to about 100μηι, were initially used to support the sorptive coating, which might be anything up to 100μηι thick. In a typical SPME fibre sampling device, a simple, spring-loaded, mechanism allows the fibre to be exposed to the environment, e.g. atmosphere or headspace above liquid or solid samples, and then retracted into the needle for storage until later being inserted into the injection port of an analysis instrument, usually a gas chromatograph. Here the fibre is heated to a suitable temperature to cause the analyte to desorb from the coating and past directly into the analytical part of the instrument.

[0004] This use of fibre form SPME devices so as to be directly compatible with the existing gas chromatograph instruments limited the use of SPME techniques in fields where the fragility of these sampler devices made them impractical. [0005] SPME devices are usually reused for many analyses. When reusing them, it is essential that all adsorbed materials are removed from the capturing matrix after each analysis. This is generally achieved by heating the "business end" of SPME device to high temperature to drive off any remaining captured compounds. The thermal cycling of the adsorber is the main degradation mechanism that limits the number of time that the SPME device can be used.

[0006] The needle configuration of the SPME devices makes them impractical for use in breath testing.

[0007] More recently, a new implementation of SPME technology, using a planar sampling device, was described in an article entitled "Analysis of the volatile chemical markers of explosives using novel solid phase micro extraction coupled to ion mobility spectrometry", by Patricia Guerra, Hanh Lai, Jose R. Almirall, in J. Sep. Sci. 2008, 31 , 2891 - 2898 and in patent specification US 8,668,873 B2. A device based on this concept is also now commercially offered under the trade name FAST by Field Forensics, Inc. of St Petersburg, Florida, USA. In each case the sampling device is a small disc, which is typically circular and typically has a surface area of each major surface of about 250 mm², and which is made of metal, plastics material or ceramic, such as glass, with one or both major surfaces coated with a vapour sorption material. The sorption material disclosed is for sorption of vapour from an explosive, from a legally controlled drug substance or from a biological hazard substance. Just as with SPME fibre, any adsorbed volatiles need to be driven out of the coating for analysis and this is achieved by heating the planar device (disc) to temperatures in excess 80° C, 250° C not being unusual.

[0008] The present invention has been made in the context of breath sampling carried out in a clinical context as a non-invasive diagnostic tool. The composition of gases in the exhaled breath varies with the physiological state of the person. Therefore, a sample of gas exhaled by a person can (in theory) be tested for the presence of a substance known to indicate a particular underlying condition. However, commercial breath tests are currently available only for a few conditions, such as the detection of alcohol blood levels, Helicobacter Pylori stomach infection (which is known to lead to peptic ulcers in some people), Irritable Bowel Syndrome, and a few other conditions, such as lactose or fructose intolerance.

[0009] The main criteria for a practical breath test are:

1. knowledge of specific biomarkers in exhaled breath for the particular condition (for example, H. Pylori stomach infection results in ammonia in the breath of a patient);

2. instruments for detecting and identifying the relevant biomarker substances; and 3. a system for getting exhaled breath into instruments for analysis.

[0010] The difficulty of getting exhaled breath into an analytical instrument for analysis is primarily due to the fact the volume of exhaled breath is large while analytical instruments are designed to deal with small volumes of gas only. Also, biomarkers of interest are present in very low concentrations, e.g. just a few ppm in the case of ammonia resulting from H. Pylori stomach infection, in this large volume of exhaled breath. This particular problem can be solved by using SPME techniques. However, known SPME devices, particularly the recently developed planar devices mentioned above, are not disposable and are reused. This imposes an additional requirement on any breath test of the need to prevent contamination of analytical instruments and to prevent transmission of bio materials from person to person, i.e. cross contamination on the SPME device. This last requirement presents a significant challenge in devising a practical breath test.

[0011] Some components typically used in a breath test, for example mouth pieces, can be disposed of after use. However, others, such as SPME devices currently available cannot be discarded because of their high cost. Furthermore, if they are made from glass, ceramics or metals then their disposal is not a straightforward, low cost affair. There are many established method for disinfecting reusable items in the medical field, but not all are practical or even suitable for items used in breath testing, specifically the SPME devices.

[0012] An object of the present invention is to devise an economical, single-use, SPME device which could be used in diagnostic breath testing, but would also have wider applicability in the environmental, law enforcement and industrial fields. Providing a disposable SPME device would also removes the need for regeneration of the active material in the SPME devices and avoid any problem in respect of the degradation in coating performance.

SUMMARY OF THE INVENTION

[0013] The present invention provides, as a first aspect, a solid-phase micro extraction (SPME) device comprising: a supporting substrate in the form of a sheet of paper board, of cardboard or of plastics material having first and second major surfaces and having first and second end regions; a layer of gas barrier material applied over the first end region of at least the first major surface; and a volatile compound sorptive coating disposed on the gas barrier material on the first major surface; the second end region of the substrate being dimensioned to serve as a handhold section of the device.

[0014] The inventors previously developed a fully disposable breath sampler, aimed at providing a breath test for H. Pylori infection, where all parts could be made from paper and easily disposable polymers. Such a breath sampler is disclosed in the applicant's earlier WO 2007/000568. In seeking to design an SPME device which would be economical as a single-use device, and easily disposed of, yet would remain effective in capture of small concentrations of analytes and transmission of same to an analytical instrument, the main problem was that when heated most potential substrate materials release gases, vapours and various by-products of compounds used in their manufacture. These would swamp any compounds of interest liberated by the SPM me device. Localised heating of the SPME adsorbing (sorptive) material is only a partial solution since it not possible to stop heat being conducted into the underlying body of the device. The solution to this problem was found to be the introduction of an impermeable barrier between the SPME adsorbing material and the body of the device itself. The main function of this barrier is to stop gases passing through. It does not have to be very thick.

Simplest implementation is to use a thin metal foil. The introduction of the concept of a barrier into the construction of the SPME device relaxes requirements on the material used for the main body of the device that offers mechanical support for the adsorbing materials.

[0015] A further useful consequence is that by using an inexpensive and easily disposable substrate material and a barrier layer, the barrier layer and the sorptive coating can be deposited on only a portion of the supporting substrate leaving a region of the substrate free to allow for handling of the device by the users. This is a significant improvement in practical fieldwork and medical situations.

[0016] Further, both the gas barrier material and the sorptive coating can be confined to only one major surface of the substrate. In practical embodiments, the gas barrier material may extend to cover both surfaces, but that is not necessary, while the sorptive material, likely to be more expensive, only needs to be applied on to a portion of the gas barrier material, conveniently a central region of said material, on one major surface of the substrate.

[0017] To this end, a depression may be formed in the central area of the first end region of the first major surface of the substrate and also in the layer of gas barrier material which is applied over said central area, and the sorptive coating is then disposed only in said

depression. This will facilitate automation in manufacture of such SPME devices. It also allows the coating to be below or no higher than the surface of the supporting substrate material and this minimises likelihood of damage to the coating when the device is deployed.

[0018] In order to avoid contamination of the sample, which may include only a small amount of the volatile compound to be detected, a further advantageous development is that a layer of non-releasable gas-impermeable plastics material may be provided as a protective surface layer over at least some of the surface of the device other than the surface of the sorptive coating. For example, the remainder of the first major surface other than the surface of the sorptive coating may be covered in this way. Also, a measure which may be used in addition or separately to aforesaid is that a peelable cover sheet of plastics material may be provided, overlying the surface of the sorptive coating, said cover sheet being removed before the relevant end region of the SPME device is exposed to the environment being tested.

[0019] In embodiments where the gas barrier material and the sorptive coating are provided on only a first major surface of the device, then as a practical measure to facilitate correct orientation in a desorption apparatus which provides heating directed only at one major surface of the device, and which includes a vapour outlet from adjacent the same said one major surface of the device, the device is advantageously provided with an asymmetric indicium which can be detected either by visual inspection by a human operator and/or automatically by sensing means of the desorption apparatus.

[0020] As regards the region of the device serving as a handhold section, at least a distal part of said handhold section, namely the part furthest from the region covered by the gas barrier layer, may be of greater width than the region covered by the gas barrier layer. This may be implemented by flaring of the outer (distal) end region or by a stepped increase in the width thereof compared to the remainder of the device, or the entire handhold section can be increased in size in either manner.

[0021] Another aspect of the invention is a desorption apparatus for use with an SPME device, wherein said apparatus comprises a head having an operative face provided with a central desorption zone and an outlet leading from said zone, with surface regions flanking said central desorption zone and with heating means for heating said flanking surface regions so that when the first end region of the first major surface of the SPME device is brought into close proximity to and/or at least partially in contact with the operative face, the operative face is capable of heating said end region of the SPME device sufficient to release volatile substances absorbed in the sorptive coating to pass through the outlet.

[0022] A further aspect of the invention is a breath sampler in combination with an SPME device wherein the sampler comprises a hollow container defining a chamber and formed of two tubular parts, namely an inner tubular part and an outer tubular sleeve, the inner tubular part being a close sliding fit within the outer tubular sleeve, the inner tubular part and the outer sleeve each having adjacent end walls at a first end of the sampler and respective apertures in said end walls, the inner tubular part being rotatable relative to the outer tubular sleeve between a first disposition in which said apertures are aligned so that said first end is open and a second disposition in which said apertures are out of alignment so that said first end is closed, at least the inner tubular part having a further aperture in its side walling which is uncovered by the outer tubular sleeve when the inner tubular part is in its first disposition so that air can pass through the chamber when said inner tubular part is in its first disposition, the inner tubular part also having a second end wall, at the opposite end of the chamber to the first end wall, which second end wall is provided with an elongate slot, and wherein the SPME device is engageable with/ removably mounted to the breath sampler with the first end region of the SPME device protruding through said slot and into the chamber of the sampler while the handhold section of said SPME device remains predominantly outside the second end wall of the inner tubular part as a hand grip to facilitate rotation of said inner tubular part from said open to said closed disposition.

[0023] Yet another aspect of the invention is desorption apparatus in combination with an SPME device, wherein said apparatus comprises a head having an operative face provided with a central desorption zone and an outlet leading from said zone, with surface regions flanking said central desorption zone and with heating means for heating said flanking surface regions and wherein the operative face when held in close proximity to and/or at least partially in contact with the first end region of the first major surface of the SPME device is capable of heating said end region sufficient to release volatile substances absorbed in the sorptive coating to pass through the outlet. Thus, while such desorption apparatus has been designed for use with an SPME device in accordance with an aspect of the present invention, it can be employed, with advantage and with suitable dimensional adaptation, with other known planar SPME devices.

[0024] Preferably, the apparatus is specifically designed to match a practical version of the SPME device as described above and in this respect the central desorption zone of said apparatus may then have an area of similar size to the area of the sorptive coating disposed on the central region of the gas barrier layer on the first major surface of the SPME device and in use said central desorption zone will overlie said sorptive coating with a gap there between. Furthermore, the operative face is preferably configured such that the surface regions flanking said central desorption zone are disposed in close proximity to or in contact with only the gas barrier material of the first end region of the first major surface of the SPME device.

[0025] The flanking surface regions of the operative face of the apparatus may suitably be configured to lie above (stand proud of) the level of the central desorption zone. In other words, the central desorption zone may itself be provided in the form of a shallow depression in the operative face of the apparatus, namely recessed to be below the level of the flanking surface regions which are used for heating.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The various aspects of the invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a practical embodiment of an SPME device in accordance with the invention;

Figure 2 is a longitudinal cross-section of the device along line ll-ll in figure 1 ; Figure 2a is an enlarged detail of the region encircled in figure 2;

Figure 3 is a perspective view of a combination of a breath sampler and the SPME device of figures 1 and 2 in accordance with a further aspect of the invention, the sampler and the device being shown separate;

Figure 4 is the same combination as in figure 3, but showing the SPME device inserted into the sampler;

Figure 4a is an end view of the sampler from the left-hand end as viewed in figure 4;

Figure 5 is the same combination as in figure 4, but showing the SPME device being used to rotate an inner part of the sampler, as in use of the combination;

Figure 6 shows the same combination as in figures 4 and 5 in a subsequent position in the sequence of operation, where the sampler is fully closed;

Figure 6a is an end view of the sampler from the left-hand end as viewed in figure 6;

Figure 7 is a schematic partial section of a combination of the SPME device of figure 1 with desorption apparatus at an initial stage of use; and

Figure 8 is a similar view to figure 7 at a subsequent stage of use of this combination. DETAILED DESCRIPTION

[0026] With reference to figures 1 and 2, a preferred practical embodiment of a solid phase micro extraction (SPME) device in accordance with the invention comprises a supporting substrate 10, a gas barrier layer 12 and a sorptive coating 14. The substrate 10, which is a small card-like sheet or tablet, provides the body of the device. It can be stamped (cut out) in an appropriate shape from commercial paperboard or cardboard. A suitable thickness is 2mm, and it may be about 7 cm long and between two and three cm wide. As shown, this substrate 10 is flared, namely tapered outwards, at 16, at one end as part of a hand hold section 18 which extends more than half the length of the device.

[0027] The gas barrier layer 12 covers the remainder of the substrate 10 at the second end of the device. The material of the gas barrier may be a 40μηι thick self-adhesive aluminium tape which is fairly straightforward to apply across the first or functional major surface 1 1 of the substrate 10. In other embodiments it could be applied around both first and second major surfaces 1 1 , 13 of the substrate 10.

[0028] As best shown in figure 2a, a shallow circular indentation 15 is formed in said first major surface 1 1 at the second end of the device. This indentation 15 may be approximately 0.2mm deep, 14mm diameter. It can be formed by stamping either before or after the metal foil is applied as the gas barrier layer 12. The indented surface is coated by a thin layer of the adsorbing material 14. This arrangement allows the top surface of the adsorbing coating 14 to remain below the level of the surface of the main body of the device. Thus this SPME device can be safely inserted into an appropriately designed breath sampler 20, as shown in figures 3 to 6, with minimal risk of damaging the adsorbing coating 14 during the process.

[0029] As regards the region of the device serving as a handhold section, at least a distal part of said handhold section, namely the pad furthest from the region covered by the gas barrier layer, may be of greater width than the region covered by the gas barrier layer. This may be implemented by flaring of the outer (distal) end region or by a stepped increase in the width thereof compared to the remainder of the device, or the entire handhold section can be increased size in this manner.

[0030] A small round hole 17 is provided asymmetrically in the hand hold section 18, in relatively close proximity to the second end which is coated with the gas barrier layer 12. The purpose of this hole 17 is to enable automatic alignment when the SPME device is placed in the specially designed desorber 30, shown in figures 7 and 8, and particularly to ensure that the coating 14 is facing in the correct direction from which heating will be applied.

[0031] In order to avoid contamination of a sample, which is to be adsorbed onto the coating 14 and which may include only a small amount of the volatile compound to be detected, a layer of non-releasable gas-impermeable plastics material may be provided as a protective surface layer over the surface of the device other than the surface of the sorptive coating 14. Also, a peelable cover sheet of plastics material may be provided, overlying the surface of the sorptive coating 14, said cover sheet being removed before the relevant end region of the SPME device is exposed to the environment being tested. Such additional plastics material layer and peelable cover sheet are not illustrated in the drawings.

[0032] A breath test for H. Pylori infection requires, for the coating 14, adsorption material that has high affinity for ammonia. Polyaniline satisfies this requirement. It has been determined, as a separate aspect of the present invention, that polyaniline is suitable for use in an SPME device and can be applied as an aqueous suspension to provide the adsorbing coating not only on the current novel SPME device, but any hitherto known planar SPME device.

[0033] To produce the device of the invention being described as this specific embodiment with regard to figures 1 and 2, the aluminium foil surface of the device on the first major surface is firstly cleaned, for example with medical wipes. Polyaniline is suspended in distilled water. Using a small clean brush the whole surface area of the indentation 15 is then painted with this suspension and allowed to dry in clean air overnight. The resulting coating is very thin so that its top surface is still below the rest of the SPME surface, i.e. within the 0.2 mm deep depression 15. Adhesion to the aluminium barrier is good, but the coating 14 can be rubbed off with a moderate effort. However the coating is unlikely to come into mechanical contact with anything during routine use of such an SPME device.

[0034] Referring to figures 3 to 6, the SPME device 10 is shown in combination with the breath sampler 20. The sampler 20 comprises a hollow container defining a chamber and formed of two tubular parts, namely an inner tubular part 22 and an outer tubular sleeve 24. The inner tubular part 22 is a close sliding fit within the outer tubular sleeve 24. The inner tubular part 22 and the outer sleeve 24 each have adjacent end walls at a first end of the sampler 20 and respective apertures 25, 27 in said end walls, as shown in figures 4a and 6a respectively (although in figures 4a and 6a only the end wall 23 of the outer sleeve 24 can be seen). The inner tubular part 22 is, accordingly, rotatable relative to the outer tubular sleeve 24 between a first disposition in which said apertures 25, 27 are aligned so that said first end is open, as shown in figure 4a, and a second disposition in which said apertures 25, 27 are out of alignment so that said first end is closed, as shown in figure 6a.

[0035] The inner tubular part 22 has a further aperture 26 in its side walling which is uncovered by the outer tubular sleeve 24 when the inner tubular part 22 is in its first disposition (figures 3 and 4) so that air can pass through the chamber when said inner tubular part is in its first disposition. In this respect, the outer tubular sleeve 24 has an open end 19 of oblique disposition so that the end margin of the sleeve 24 does not overlie the aperture 26 in the figure 3/figure 4 disposition of the inner tube 22, but does cover the aperture 26 in the figure 6 disposition of the inner tube 22. The aperture 26 in the side walling of the inner tubular part 22 is elongate and extends circumferential ly of said inner tubular part 22.

[0036] The inner tubular part 22 also has a second end wall 28 at the opposite end of the chamber to the first end wall 21 , which second end wall 28 is provided with an elongate slot 29. This elongate slot 29 extends generally across a diameter of the end wall 28 and in a direction substantially perpendicular to the aperture 26 in the side walling of the inner tubular part 22. [0037] As shown, the SPME device is adapted to engage with, i.e. be removably mounted to the breath sampler 20 with the first end region 1 1 of the SPME device being inserted through said slot 29 and projecting into the chamber of the sampler while the handhold section 18 of said SPME device remains predominantly outside the second end wall 28 of the inner tubular part 22. The protruding part of the hand hold section 18 thereby serves as a hand grip to facilitate rotation of said inner tubular part 22 from said open to said closed disposition, namely from the position shown in figure 4, the open disposition, through figure 5 where the inner part 22 is turned through approximately 90°, to figure 6 where the inner part 22 has been turned through approximately 180° to the closed disposition of the apertures 25, 27 and 26. Moreover, the SPME device cannot be inserted too far as the extent of its insertion is limited by the flared edges 16.

[0038] In use, the breath sampler 20 is provided in its open condition (figure 3). A disposable mouthpiece (not shown) may be attached to the end of the breath sampler adjacent the end wall 23. A patient breathes out through the disposable mouthpiece or directly into that end of the sampler, thus through the aligned openings 25, 27. An early portion of the exhaled breath may pass completely through the sampler, exiting via the aperture 26. At the end of the patient's exhalation, the sampler is immediately moved into the closed position of figure 6, by turning the inner tube 22, using the handhold section 18 of the SPME device. A later portion of the exhaled breath is thereby captured within the chamber of the breath sampler and exposed to the coating 14 of the SPME device. A further advantage of the positioning of the SPME device by insertion into the slot 29 is that area of the coating material 14 is then mounted centrally in the chamber for maximum exposure to the breath sample. Its position extending perpendicular to the plane of the outlet aperture 26 is especially preferable in order that whichever way around the device 10 is inserted through the slot 26, the coating 14 will be exposed to maximum extent as the patient's breath flows towards the outlet aperture 26. After a sufficient time following capture of the patient's breath, a period to be predetermined but likely no more than a few minutes, the SPME device can then be removed from the sampler and processed in desorption apparatus to transfer captured volatile substances to known analytical equipment.

[0039] In order to heat the SPME device effectively and economically so that the adsorbing coating 14 releases the captured compounds of interest to an adequate extent, and in a manner which is efficiently transmitted to known analytical equipment, a special desorption apparatus 30 has been designed. Indeed, the design of the above described SPME device has itself been tailored to this apparatus. In other words, the two items have necessarily been designed with a view to joint use. In the prior art it was proposed to heat the whole SPME device. Now, the sorptive coating can be subject to only localised heating for simplicity and to remove need for considering the speed of the heat transfer from the heater through the body of the device to the coating, and this is found to work well.

[0040] As shown in figures 7 and 8, albeit schematically, desorption apparatus 30 in accordance with the invention comprises a head 32, suitably made of stainless steel, having an operative face provided with a central desorption zone 34 and an outlet 36 leading from said zone. The operative face also has surface regions 37 flanking said central desorption zone 34. Inside the head 32, heating means, depicted here as tWo low-power tubular heaters 38, are provided for heating said flanking surface regions 37.

[0041] In use, it may be sufficient for the operative face to be held in close proximity (perhaps at a spacing in the region of 1-2 mm) to the first end region 1 1 of the first major surface of an SPME device as described in relation to figures 1 to 6 above, for the metal foil gas barrier material 12 and the coating material 14 in that end region to be sufficiently heated to release volatile substances held in the sorptive coating 14 to pass through the outlet 36. As shown, the apparatus is specifically designed to match a practical version of the SPME device as described above and the central desorption zone 34 has an area of similar size to the area of the sorptive coating 14 so as to overlie said sorptive coating with a narrow gap there between. Moreover the operative face of the head 32 has the surface regions 37 flanking said central desorption zone 34 standing proud of the level of the central zone so that they are disposed in closer proximity to the gas barrier material 12 surrounding the coating 14. In other words, the central zone 34 is in the form of a shallow depression in order to provide a cavity for receiving the evaporated volatile compound from the coating 14. In some circumstances where enhanced heat transfer is required, the heated flanking regions 37 may be brought at least partially into contact with the metal foil material 12 surrounding the coating 14. This also serves to isolate the adsorbing coating 14 from its surroundings. If it is desired to hermetically isolate the coating 14 from the surrounding, an appropriate sized O-ring from a suitable material, such as Viton, can be provided between the desorber head 32 and the SPME device, just outwardly of the area of the coating 14. However in practice it has been found that this is an unnecessary complication for most applications.

[0042] Two optional gas inlets 35 are also shown for applications where it is necessary to transport the desorbed compounds from the coating 14 into an analytical instrument by means of a stream of carrier gas.

[0043] A thermocouple (not shown) may usefully be placed in contact with the desorber head 32 to monitor its temperature. A simple feedback loop can be implemented to stabilise temperature to within ±1 degree of the set working temperature. When the heated desorber head 32 is brought into close proximity or into contact with the SPME the adsorbed gases are quickly released (in less than 2 seconds) from the coating 14 and either diffuse automatically into an analyser through the output port 36 or are swept into it by appropriate flow of neutral gases from the inlets 35.

[0044] For use in a breath test for H. Pylori infection, 80 ° C was the minimum temperature needed for ammonia desorption and the optimum was found to be 120 ° C.

[0045] A tiltable and movable platform 39, as shown, may be provided as part of the apparatus 30 for reception of the SPME device, namely placement thereon by an operator, and automatically transporting same into position with the area of the depression 15 and the sorptive coating 14 immediately below the central desorption zone 34. This ensures the optimum positioning for quick and efficient heating and extraction of the volatile compounds.

[0046] An optical sensor (not shown) is advantageously provided in the head 32 to detect the presence of the small hole 17 provided asymmetrically in the hand hold section 18 of the SPME device. This is to ensure that the SPME device is correctly oriented with the patch of sorptive coating 14 directly facing the central zone 34 and surrounded by heating means 37, 38. So if the whole 17 is not detected, some suitable form of visual or audible indicator can be provided and the heating means 38 may not be switched on, until the device has been appropriately repositioned or turned over. Obviously, any other suitable form of alignment indicator and/or sensor therefor could alternatively be provided in other embodiments.

[0047] While such desorption apparatus 30 has been designed for use with an SPME device in accordance with the present invention, said apparatus can be employed, with advantage and with suitable dimensional adaptation, with other known planar SPME devices to provide heating directed towards any one surface of the SPME device.

[0048] The invention is not restricted to the details of any forgoing embodiments. Many variations in the configurations, dimensions and materials used in respect of the SPME device, the breath sampling device and desorption apparatus can be envisaged. In particular, in respect of the SPME device, the depression 15 may not be present, and the area of the coating, with or without being applied in a depression, may be of substantially square or rectangle shape rather than circular.

[0049] Many other commercially available materials may be used as sorptive coatings in other embodiments of the invention constructed for other end user purposes, such as other breath testing to aid medical diagnostics and screening, i.e. other than a breath test for H. Pylori infection, or environmental monitoring. Obviously, the sorptive coating material chosen will be appropriate for adsorption of the compound of interest, whether biomarker or other compound to be detected. Commercially available materials for this purpose include: polydimethylsiloxane (PDMS), polyacrylate (PA), polydimethylsiloxane/divinylbenzene (PDMS/DVB),

divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS),

carboxen/polydimethylsiloxane (CAR/PDMS), carbowax-Polyethylene Glycol (PEG), carbowax- divinylbenzene (CW/DVB), carbowax/templated resin (CW/TPR). Polymeric phase with imbedded porous particles coatings PDMS/DVB CAR/PDMS CW/DVB CW/TPR. These materials and blends are already known per se for use to coat commercial available SPME fibres. Sigma-Aldrich are suppliers of SPME fibres and the aforesaid coating materials which have hitherto been used for such fibres.

[0050] Other materials reported in the literature, which may also be suitable for use in modified embodiments of SPME device in accordance with the invention, for explosive or biohazard detection and identification are polymethylvinylsiloxane (PMVS), polypyrrole (PPY), polysilicone fullerene (PF), polycrystalline graphites.

[0051] Although designed with breath tests in mind, an SPME device in accordance with the invention can be used on its own, and optionally in combination with desorption apparatus of the invention, for other applications. Specifically the SPME can be used for extraction of volatiles from any air samples or environments or head spaces, whether for medical diagnostics, environmental monitoring or industrial commercial for other purposes. Also, with suitable adaptation, namely suitable choice of a substrate material which is not impaired by exposure to liquids (namely use of a plastics material instead of paper-based material) or use of a waterproofing coating there over, the SPME can be used for extraction of dissolved volatiles, that is to say substances dissolved in water or other liquids. A further specific application could be the monitoring of infection of wounds by reference to volatile compounds which are given off by certain infective bacteria. In this case, suitably configured SPME made of suitable materials could be incorporated into or inserted into wound dressings and bandages.

[0052] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0053] Features described in conjunction with a particular embodiment of the invention are to be understood to be applicable to any other embodiment described herein unless incompatible therewith.

Claims

1. A solid-phase micro extraction (SPME) device comprising: a supporting substrate in the form of a sheet of paper board, of cardboard or plastics material having first and second major surfaces and having first and second end regions; a layer of gas barrier material applied over the first end region of a least the first major surface; and a volatile compounds sorptive coating disposed on the gas barrier material on the first major surface; the second end region of the substrate being dimensioned to serve as a handhold section of the device.

2. An SPME device as claimed in claim 1 wherein the sorptive coating is disposed on only a portion of the layer of gas barrier material on the first major surface of the substrate.

3. And SPME device as claimed in claim 2 wherein said portion is a central region of the gas barrier layer on the first major surface of the substrate.

4. An SPME device as claimed in claim 3 wherein a depression is formed in the central area of the first end region of the first major surface of the substrate and also in the layer of gas barrier material which is applied over said central area, and the sorptive coating is disposed only in said depression.

5. An SPME device as claimed in any preceding claim wherein a layer of non-releasable gas-impermeable plastics material is provided as a protective surface layer over the surface of the device other than the surface of the sorptive coating on the first end region of the first major surface.

6. An SPME device as claimed in any preceding claim wherein a peelable cover sheet of plastics material overlies the surface of the sorptive coating.

7. An SPME device as claimed in any preceding claim wherein the gas barrier material is a metal foil.

8. An SPME device as claimed in any preceding claim provided with an asymmetric

indicium to facilitate correct orientation in a desorption apparatus which provides heating directed only at one major surface of the device, and which includes a vapour outlet from adjacent the same said one major surface of the device.

9. An SPME device as claimed in any preceding claim wherein at least a distal part of the handhold section is of greater width than the first end region.

10. An SPME device as claimed in any preceding claim wherein the sorptive coating comprises polyaniline.

1 1. A breath sampler in combination with an SPME device as claimed in any preceding

claim.

12. A breath sampler in combination with an SPME device as claimed in claim 11 wherein the sampler comprises a hollow container defining a chamber and formed of two tubular parts, namely an inner tubular part and an outer tubular sleeve, the inner tubular part being a close sliding fit within the outer tubular sleeve, the inner tubular part and the outer sleeve each having adjacent end walls at a first end of the sampler and respective apertures in said end walls, the inner tubular part being rotatable relative to the outer tubular sleeve between a first disposition in which said apertures are aligned so that said first end is open and a second disposition in which said apertures are out of alignment so that said first end is closed, at least the inner tubular part having a further aperture in its side walling which is uncovered by the outer tubular sleeve when the inner tubular part is in its first disposition so that air can pass through the chamber when said inner tubular part is in its first disposition, the inner tubular part also having a second end wall, at the opposite end of the chamber to the first end wall, which second end wall is provided with an elongate slot, the SPME device being removably mounted to the breath sampler with the first end region of the SPME device protruding through said slot and into the chamber of the sampler while the handhold section of said SPME device remains predominantly outside the second end wall of the inner tubular part as a hand grip to facilitate rotation of said inner tubular part from said open to said closed disposition.

13. A breath sampler in combination with an SPME device as claimed in claim 12 wherein the outer tubular sleeve has an open end of oblique disposition relative to the axis of the container so that an end margin of the outer sleeve adjacent said open end only covers the further aperture in the side walling of the inner tubular part in said second disposition when the first end of the container is closed.

14. A breath sampler in combination with an SPME device as claimed in claim 12 or 13

wherein the elongate slot in the second end wall of the inner tubular part, into which the SPME device is insertable, extends substantially across a diameter of the container.

15. A breath sampler in combination with an SPME device as claimed in claim 14 wherein the aperture in the side walling of the inner tubular part is elongate and extends circumferentially of said inner tubular part and the elongate slot in the second end wall of the inner tubular part, into which the SPME device is insertable, extends in a direction substantially perpendicular to the aperture in the side walling of the inner tubular part.

16. Desorption apparatus in combination with an SPME device as claimed in any of claims 1 to 9, wherein said apparatus comprises a head having an operative face provided with a central desorption zone and an outlet leading from said zone, with surface regions flanking said central desorption zone and with heating means for heating said flanking surface regions and wherein the operative face in close proximity to and/or at least partially in contact with the first end region of the first major surface of the SPME device is capable of heating said end region sufficient to release volatile substances absorbed in the sorptive coating to pass through the outlet.

17. The combination as claimed in claim 12 wherein the SPME device is as claimed in claim 3, and wherein the central desorption zone of said apparatus has an area of similar size to the area of the sorptive coating disposed on the central region of the gas barrier layer on the first major surface of the SPME device and overlies said sorotive coating with a gap there between.

18. The combination as claimed in claim 12 wherein the SPME device is as claimed in claim 3, and wherein the operative face is configured such that the surface regions flanking said central desorption zone are disposed in close proximity to or in contact with only the gas barrier material of the first end region of the first major surface of the SPME device.

19. The combination as claimed in claim 12, 13 or 14 wherein the flanking surface regions of the operative face of the apparatus lie above the level of the central desorption zone.