Miniature solid phase microextraction holder

Abstract

A miniature solid phase microextraction (SPME) holder. The miniature holder enables transportation and field use of SPME fibers which are very fragile and will break with the slightest impact. Also, the holder prevents cross contamination of samples during transport. The SPME holder consists of a barrel with two end caps, and includes a plunger that is connected to a commercial SPME fiber assembly, one end cap filing over the SPME needle on one end of the barrel and the other end cap fitting over the plunger. The end caps are provided with seals that give the holder a hermetic seal. The holder enables effective field use for the collection, isolation, and concentration of trace amounts of residues air, soil, etc.

Description

RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. application Ser. No. 09/834,138, filed Apr. 12, 2001, entitled Solid Phase Microextraction Field Kit.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to the collection and characterization of residues, particularly to a holder for solid phase microextraction (SPME) fibers, and more particularly to a miniature SPME holder for field applications.

[0003] Over the last decade, extensive efforts have been carried out for development methods for characterization of various chemicals, particularly for the characterization of high explosives, chemical weapons, and biological weapons. These activities have centered on the collection, isolation, and concentration of trace amounts of these chemical residues in air, soil, vegetation, swipe, and liquid samples. Considerable resources have been applied to developing consistent and reliable methods for field analysis of high explosives and chemical weapons related materials.

[0004] Solid Phase Microextraction (SPME) is a widely recognized approach for the collection of various chemical residues, and SPME fibers and syringes are commercially available. SPME requires no solvents, is sensitive to low nanogram signature species, and can be repeatedly used in the field for the characterization of complex samples. A significant attribute of SPME fibers is their exceedingly high collection efficiencies. No chemical pretreatment or solvent extractions are necessary when using SPME fibers with GCS or GCS-MS instrumentation. However, there are some inherent problems with field SPME. SPME fibers tend to be very fragile and will break with the slightest impact. This makes transportation of SPME difficult in the field. Also, since SPME fibers are used for the sampling of potentially hazardous materials, the fibers need to be transported in a container that would prevent collected potentially lethal materials from contaminating the surroundings during transportation, as well as prevent cross contamination of different samples.

[0005] The SPME field kit described and claimed in above-referenced application Ser. No. 09/834,138 provides a solution to the above-referenced problems and enables effective use of SPME for field analysis. The SPME field kit includes an air tight container in which is located a number of hermetically sealed individual transport containers or tubes within which are located SPME syringes, with the fiber of each syringe provided with a protective cap. The transport container or tubes each include a sampling port wherein material collected by one SPME fiber located within the transport container or tube can be transferred to another SPME fiber via the sampling port. The kit also contains a device for extracting and/or inserting the protective cap on the SPME fiber, as well as various spare parts, protective gloves and an instruction manual.

[0006] SPME holders are also commercially available by the manufacture of the SPME fibers, Sigma Aldrich and Supelco, but have not been effective for field applications.

[0007] One disadvantage of the above-referenced field kit is the size of the transport containers or tubes within which are located the SPME syringes. The present invention provides SPME holder which is small and robust. This miniature SPME holder is ideal for transport, collection of highly toxic and pathogenic samples, safe opening in the laboratory, and storage of important, highly toxic samples for exact characterization in the laboratory and in the field. Thus, the present invention provides a means for the safe collection and handling of highly toxic, unknown samples by first responders to the scene of an unknown release. Basically, the SPME holder of this invention is composed of a barrel section, about the size of a writing pen, and a pair of end caps which removably attached to the barrel within which the SPME fiber is retained, and the barrel and/or end caps are provided with seals for the prevention of leakage from a contaminated SPME needle.

SUMMARY OF THE INVENTION

[0008] It is an object of the present invention to provide a solid phase microextraction (SPME) holder which is field-deployable.

[0009] A further object of the invention is to provide an SPME holder, small in size, that contains all necessary hardware for the proper collection of trace compounds in complicated samples.

[0010] Another object of the invention is to provide a field-deployable SPME holder which includes an SPME fiber hermetically sealed in its own transport tube to avoid any possibility of cross contamination.

[0011] Another object of the invention is to provide hermetically sealed transport containers or holders for SPME fibers.

[0012] Another object of the invention is to provide an SPME holder with a protective tube for the SPME, and to provide a device for insertion and extraction of the fiber.

[0013] Another object of the invention is to provide an SPME holder which is small, lightweight, robust, and field deployable.

[0014] Another object of the invention is to provide a miniature SPME holder which is ideal for transport, collection of important, highly toxic samples for exact characterization in the laboratory and in the field.

[0015] Another object of the invention is to provide a miniature holder for SPME fibers when enables safe collection and handling of highly toxic, unknown samples by first responders to a release of various materials.

[0016] Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The present invention involves an SPME field deployable holder for use in the collection, isolation, and concentration of trace amounts of high explosives (HE), chemical weapons (CW), biological warefare (BW) related materials, and other residues in air, soil, vegetation, swipe, and liquid samples, and particularly for field analysis of HE and CW-related materials. The holder of this invention satisfies the needs for a field-deployable SPME system for the proper collection of trace compounds in complicated samples.

[0017] The invention broadly is a small, very robust SPME sampling apparatus, and more specifically is a miniature SPME fiber holder. The miniature SPME holder resolves the problems of the fragile nature of the SPME fiber, the problem of cross contamination of the samples, and the bulky size constraints.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated into and form a part of the disclosure, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention.

[0019] FIG. 1 illustrates an SPME transport tube or holder of above-referenced application Ser. No. 09/834,138.

[0020] FIG. 2 illustrates an actual size embodiment of the miniature SPME holder made in accordance with the present invention to illustrate the size comparison of the two holders.

[0021] FIG. 3 is an enlarged view of the FIG. 2 holder, which is basically composed of a two-section sample body or barrel and two end caps.

[0022] FIG. 4 is a cross-sectional view of the FIG. 3 SPME holder.

[0023] FIG. 5 illustrates an embodiment of the barrel section of the SPME holder with the end caps removed, and with the SPME fiber retracted within a sheath.

[0024] FIG. 6 is similar to FIG. 5 but with the SPME fiber tip extending from the sheath for exposure to a sample.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention involves a miniature SPME holder which is field-deployable. Since there are some inherent problems with field use of SPME because the SPME fibers, such as those made commercially by Sigma Aldrich and Supelco, tend to be very fragile and will break with the slightest impact. This make transportation of the SPME difficult in the field. Also, because of the very absorbent nature of SPME, cross contamination of samples during transport must be prevented. Also, there has been a new for a field SPME device that is small, lightweight, and robust. The invention is a small, very robust SPME sampling apparatus which provides solutions to the problems of the fragile nature of the SPME fiber, the problem of cross-contamination of the samples, and bulky size constraints. The SPME device of this invention enables the collection, isolation, and concentration of trace amounts of, for example, chemical weapons (CW) residues in air, soil, vegetation, swipe, and liquid samples. The miniature SPME holder is ideal for transport, collection of highly toxic samples for exact characterization in the laboratory and in the field. The SPME holder of the invention is about the size of a typical pen or pencil and can readily be transported in a user's shirt pocket, for example, and thus can be readily carried for the safe collection and handling of highly toxic, unknown samples, by first responders to the scene of a WMD release, for example.

[0026] The SPME holder consists of a stainless steel barrel with an &sgr;-ring seal, a stainless steel plunger that is connected to a commercial SPME fiber assembly, a stainless steel head cap with an &sgr;-ring seal, and two titanium end caps that fit over an SPME shielth which retains the SPME fiber on one end the plunger at the other. The end caps with &sgr;-ring seals give the unit a hermetic seal.

[0027] One of the titanium end caps has Teflon insert that prevents out-gassing of the SPME fiber and also prevents vibration and movement of the SPME shield or needle. Preventing movement is critical as this prevents breakage of the fiber or removal of the SPME polymer coating on the fiber.

[0028] The barrel houses the SPME fiber assembly, the plunger, the head, and is secured to the end caps. It has milled grooves that guide the plunger and allows the SPME fiber to be locked in the exposed (expanded) position or the travel (retracted) position. The barrel also has a Viton &sgr;-ring that seals against on end cap.

[0029] The plunger is threaded on one end so that the commercial SPME fiber assembly can be threaded into it. The plunger also has a threaded hole that accommodates a set screw. The set screw moves along the grooves and guides the plunger and SPME fiber assembly up and down the barrel.

[0030] The head assembly threads into the barrel and holds the SPME fiber assembly firmly in place. The head has a Viton &sgr;-ring that creates a seal when the end cap is attached.

[0031] Referring now to the drawings, FIG. 1 illustrates the transport tube or SPME holder of above-referenced application Ser. No. 09/834,138, and is illustrated to show size comparison with the embodiment of the miniature SPME holder of FIGS. 2, shown in greater details in FIGS. 3-7. The transport tube or holder of FIG. 1, generally indicated at 10, comprises two housing sections 11 and 12, interconnected by a pair of twist and lock mechanisms, not shown, located within portion 13 of housing section 11, with housing sections 11 and 12 having external grooves 14 and 15, respectively. The FIG. 1 transport tube has a length of 22.5 cm and diameter of 2.7 cm.

[0032] The embodiment of the miniature SPME holder of FIGS. 2 and 3, generally indicated at 20, comprises two body or barrel sections 21 and 22 and two end sections or end caps 23 and 24, with barrel sections 21 and 22 having a threaded interconnection, as seen in FIG. 4, and wherein end caps 23 and 24 extend over and are snap-action secured to barrel sections 21 and 22 by &sgr;-ring seals, as shown in FIG. 4. The miniature holder of FIG. 2 has a length of 14.5 cm and diameter of 9 mm.

[0033] As seen in FIG. 4, body or barrel section 21 has a longitudinally extending opening 25 with internal threads 26 at one end, and is provided with an external cut-away or reduced diameter section 27 at an opposite in which is a groove 28 retaining an &sgr;-ring seal 29. Body or barrel section 22 includes a reduced outer diameter or cut-away section 30 having outer threads 31 which cooperate with threads 26 of barrel section 21, and a reduced outer diameter section or cut-away 32 having a groove 33 therein for retaining an &sgr;-ring seal 34. Barrel section 22 is also provided with a central longitudinally extending opening of two difference diameter sections 35 and 36. As seen in FIG. 4, end cap 24 has an opening 37 in which a Teflon member or seal 38 having a central opening 39 is mounted. Teflon seal 38 includes a tapered surface 40 to provide easier entrance into opening 39 by a sheath or tube 41 of a plunger assembly generally indicated at 42 and which includes barrel sections 21 & 22, and with component thereof positioned in opening 25 of barrel section 21, with the sheath 41 extending through opening sections 35 and 36 of barrel section 22. The exterior of the plunger assembly 42 is illustrated in FIGS. 5 and 6, with certain of the interior components being illustrated in FIG. 4. The plunger assembly 42, as shown in FIG. 4, includes an annular member 43 located adjacent section 30 of barrel section 22 and having an opening 44 through which a tube or rod 41′ passes and extends into sheath 41. Member 43 functions an end support for a spring 45 with the opposite end of the spring 45 abutting a member 46 removably secured to a plunger on pusher 47 within end cap 23. As seen in FIG. 4, the plunger assembly 42 is located intermediate end caps 23 and 24 when in its transport or storage position. Spring 45 rod 41′, member 43 and member 46 constitute components of a commercial SPME fiber assembly, with an SPME fiber 48 being operatively mounted in member 43 and connected to rod tube 41′, and is movably mounted in sheath 41 as seen in FIG. 6 when the plunger or pusher 47 is moved inwardly, as described hereinafter with respect to FIGS. 5 and 6.

[0034] As seen in FIG. 4, but shown specifically in FIGS. 5 and 6, reduced diameter end section 27 of end cap 21 also includes a U-shaped groove having end leg sections 49 and 50 and an interconnecting center section 51. A member, 52, such as a set screw, is mounted in plunger or pusher 47 and is moved by rotational (arrow a) and lateral movement (arrow b) of pusher 47 against spring 25 from groove leg section 49 through groove section 51 and into groove leg section 50 as seen in FIG. 6 whereby rod 41′ extends into sheath 41 and the SPME fiber 48 is extended from sheath 41 for exposure to the environment. Upon exposure of fiber to a sample, the pusher 47 is rotated as shown by arrow c and is moved outwardly as indicated by arrow d by spring 25, as shown in FIG. 5, whereby the exposed SPME fiber is withdrawn into sheath 41, after which end caps 23 and 24 are positioned over reduced diameter sections 27 and 32 of barrel sections 21 and 22 and retained and sealed by the &sgr;-ring seals 29 and 34 via a frictional contact between the seals and the end caps. Note that the end of sheath 41 is easily inserted into the Teflon member or seal 38 via the tapered surface 40. After exposure, SPME fiber 48 can be safely transported without the possibility of breakage or leakage to a point of analysis, after which the end caps 23 and 24 are removed, and the pusher is rotated and moved laterally to again expose the end of SPME fiber 48. It has thus been shown that the present invention provides a small, lightweight, robust holder for SPME fibers and which provides safe transport of the unexposed or exposed fiber, and includes seals which prevent any cross-contamination by leakage from the exposed fiber. The SPME holder can be readily transported and utilized by any first responder to a scene of contamination, such as a WMD release.

[0035] While a specific embodiment of the invention and exemplary materials have been illustrated and described to exemplify and teach the principles of the invention, such are not intended to be limiting. Modifications and changes may become apparent to those skilled in the art, and it is intended that the invention be limited only by the scope of the appended claims.

Claims

1. A holder for an SPME fiber, comprising:

a plunger assembly in which an SPME fiber is adapted to be mounted, and

a pair of end caps removably mounted to opposite ends of said plunger assembly in a sealing relation to the plunger assembly.

2. The holder of claim 1, wherein said plunger assembly includes a pair of removably interconnect barrel sections, each having an opening extending longitudinally therethrough and in which an associated SPME fiber is adapted to be mounted.

3. The holder of claim 2, wherein a first of said pair of barrel sections is provided with a sheath mounted in said opening therein and extending from said first barrel section for protecting an associated SPME fiber, and wherein a second of said pair of barrel section is provided with a pusher and constructed to be rotationally and laterally moved to enable movement of an associated SPME fiber within said sheath for exposing or retracting such an associated SPME fiber.

4. The holder of claim 2, wherein each of said pair of barrel sections is provided with seal which provides sealing with and retaining of an associated end cap.

5. The holder of claim 4, wherein an outer end section of each of said pair of barrel section has a reduced cross-section, a groove located in each said reduced cross-sections, and wherein said seal comprises an &sgr;-ring mounted in each groove.

6. The holder of claim 3, wherein one of said end caps includes a member for retaining an outer end of said sheath.

7. The holder of claim 3, wherein said second of said pair of barrel sections is constructed to include a U-shaped groove having a pair of leg sections and an interconnecting section, and wherein said pusher is provided with a member that is movable along said U-shaped groove when said pusher is moved rotationally and laterally.

8. The holder of claim 3, in combination with an SPME fiber assembly located with said openings of said pair of barrel sections, and comprising a spring, a pair of end members, and an SPME fiber, and wherein lateral movement of said pusher in one direction causes compression of said spring and outward movement of said SPME fiber located within said sheath for exposure of an end of said SPME fiber to a selected condition, and wherein lateral movement of said pusher in an opposite direction withdraws said SPME fiber to be within said sheath.

9. The combination of claim 8, wherein one of said pair of end members of said SPME fiber assembly is positioned in an abutting relation with an inner end of one of said pair of barrel sections.

10. The combination of claim 8, wherein another of said pair of end members of said SPME fiber assembly is removably secured to said pusher.

11. The combination of claim 8, wherein said SPME fiber assembly additionally includes a longitudinally extending member mounted to at least contact an inner end of said SPME fiber, extend through said spring and through one of said pair of end members, and at least contact another of said pair of end members, whereby lateral movement of said plunger causes lateral movement of said longitudinally extending member and movement of said SPME fiber.

12. An SPME holder, comprising:

a pair of interconnected barrel sections each having an opening extending therethrough,

a pair of end caps operatively mounted to said pair of barrel sections,

each of said pair of barrel sections having an opening extending therethrough,

one of said pair of barrel sections having a sheath extending therefrom,

another of said pair of barrel sections including a pusher operatively connected thereto,

an SPME fiber assembly positioned in said openings in said pair of barrel sections and having an SPME fiber extending into said sheath, a pair of end members with one abutting an end of said one of said pair of barrel sections and another removably mounted to said pusher, a spring located intermediate said pair of end members, and a longitudinally extending member within said spring and at least adapted to contact said SPME fiber and said another end member,

whereby lateral movement of said pusher causes movement of said SPME fiber within said sheath.

13. The SPME holder of claim 12, wherein said another of said pair of barrel sections includes a groove, and wherein said pusher includes a member adapted to move along said groove.

14. The SPME holder of claim 12, wherein one of said end caps is provided with a member for retaining an end of said sheath.

15. The SPME holder of claim 12, wherein each of said barrel sections is provided with a seal member which both seals with and retains an associated end cap thereon.

16. The SPME holder of claim 15, wherein each seal member comprises an &sgr;-ring.

17. The SPME holder of claim 12, wherein each of said pair of interconnected barrel sections includes a threaded end section for removably interconnecting said barrel sections.

18. The SPME holder of claim 12, wherein each of said pair of barrel sections include an outer reduced diameter end section, said pair of end caps being mounted to said reduced diameter end sections.

19. The SPME holder of claim 18, wherein each of said reduced diameter end sections is provided with a groove, and an &sgr;-ring positioned in said groove.