CA2171016A1

CA2171016A1 - A sample container

Info

Publication number: CA2171016A1
Application number: CA 2171016
Authority: CA
Inventors: Richard Narvaez
Original assignee: Individual
Current assignee: WL Gore and Associates Inc
Priority date: 1994-09-01
Filing date: 1994-10-17
Publication date: 1996-03-07
Also published as: EP0726808A1; WO1996006678A1; JPH09504997A; AU7982994A

Abstract

A container is provided comprising expanded porous polytetrafluoroethylene that is used to hold a matrix with analyte that is undergoing physical, thermal, or extraction analysis. The container may be of any shape but is preferable in tubular shape having an inlet side, a sealed side, and an interior space.

Description

P ~71016 , TITLE OF THE INVENTION

A SAMPLE CONTAINER

FIELD OF THE INVENTION

An inert sample container is provided comprising expanded porous polytetrafluoroethylene for holding an analyte within a matrix that is to undergo analysis. The conlainer may be employed for general chemical and clinical 10 analyses in toxic~layy or general chemistry purposes; for environmental c~l'ection such as water analysis soil analysis as well as biological analysis.

BACKGROUND OF THE INVENTION

The storage Iranspo,lc,lion and actual analysis of sample analytes present sig"ificdnt pr.b'~ms requiring a great deal of time in obta,n;ng a sample and then pr~pafing it for the appropriate ana ysis. It is desi, dbl~ to reduce the time and p~padr_~tion necess~ry for such analysis including but not limited to physical thermal and eAlfaclion analyses. In addition some analytical techn ~ues require samples to be held within containers during analysis which require s~hsequent extensive cleaning of the containers after the analysis has been completed.
As an exa"l~'e U,e~""al deso",Uon analysis requires that samples to be analyzed be placed directly into stainless steel quartz or glass tubes which are then placed within a . ha"~ber of the equipment. After the analysis is complete, these tubes must be thoroughly cleaned so that they may be used again. This is eAb~",ely cumbersome and ineffective as often a residue is deposiled on the tube walls after the analyte has been desorbed into the vapor phase and the matrix of the analyte has been destroyed. Other tubes may have walls lined with polytetrafluoroethylene (not porous PTFE) but also require the use of addilional ",alerials such as glass wool to keep particles contained within the tubes. Such tubes cannot be sealed as purge gas must be allowed to pass through the sample. There is a need for a simple contain~
to hold the matrix with analyte for analysis and eliminate the need for extensive cleaning of tubes.

``i 2 1 ~

SUMMARY OF THE INVENTION

An inert sample container is provided comprising expanded porous polytetrafluoroethylene for holding a matrix with analyte that is to undergo 5 analysis wherein the container has an inlet, walls that form an interior space therein, and at least one sealed end. Preferably the expanded porous polytetrafluoroethylene has pores with an average size of between 0.1 and 20.0 ~lm in diameter and a porosity of between 10 and 90% and wherein the analysis may be performed at a temperature of less than 360C. The 10 container may have a tubular or rectangular shape. The container may be used for many different types of analysis.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a per~pecli~/e view of the tubular container.
Figure 1 a is a longitudinal cross-sectional view of the tubular container.
Figure 1 b is a transverse cross-sectional view of the tubular container.
Figure 2 is a perspective view of a rectangular container of the present 20 invention.
Figure 2a is a longitudinal cross-sectional view of the reclangular container.
Figure 2b is a transverse cross-sectional view of the rectangular container.
DETAILED DESCRIPTION OF THE INVENTION

A container for holding a matrix and an analyte for analysis is provided.
The analyte may be in liquid, gas or solid form and the matrix holding the 30 analyte may be soil, plastic, paper, powders, and liquid polymers. The container is preferably made entirely of expanded polytetrafluoroethylene thereby causing it to be inert so that the analyte does not becG",e contaminated by any offgassing from the constituents of the container.
Moreover because the ex~,anded polytetrafluoroethylene is porous, volatile 35 gasses from the analyte are able to diffuse from the container so that both the vapor portion of the analyte can be analyzed as well as any liquid portion. The matrix holding the analyte may be degraded during analysis and its residue remains within the walls of the conlainer.

~- 2171016 The container may be constructed to be sufficiently rigid so that it is resilient and capable of holding a liquid or other amorphous shape of which matrix may assume within the container. The resiliency of the container depends on the ~l,enyll, and thickness of the expanded porous 5 polytetrafluoroethylene used.
The expanded porous polytetrafluoroethylene is made according to the procedures described in U.S. Patent Nos.4 187 390 and 3 953 566. More specifically coagulated dispersion polytetrafluoroethylene (PTFE) is lightly lubricated and extruded as a paste through an annular die extruder. In a 10 series of heating and stretching steps the lubricant is evaporated away and the PTFE structure is expanded such that the present void space or porosity is finally between 10 to 95% and is preferably from 70 to 85%. The material is also heated to above its crystalline melt te",per~lure. A most preferable porosity for the material is about 70%. The sele~t;on of porosity is ultimately 15 dependent on the prope,lies of the i"ateria:s to be analyzed so that they canbe secured within the container but allow gasses to be ultimately released during analysis.
The size of the individual pores can also be selected and is dependent on the properties of the matrix and analyte. Here again the size of the pores 20 is chosen so that vapors of the analyte may be released from the container while a liquid or solid matrix is held within the container without loss. The size of the pores may range from 0.1 to 20.0 ~m. in dia,.,eter and is preferably about 3.5 ~m. The size of the pores and percent porosity can be varied depending on the different conditions under which the expanded porous PTFE
25 is made.
Similarly the wall thickness of the container may vary depending on the nature of the materials used for analysis. Generally the wall thickness of the container is about 1 mm.
The container may be constructed so that it has the necess~ry cross-30 section to hold the matrix and analyte underya.ng analysis. A preferableconstruction includes a tubular structure as shown in Figures 1 1 a and 1 b wherein one end of the tube is sealed. This may be accG",p!ished by any suitable sealing means and may include heat sealing with the use of an adhesive such as polyethylene or a melt-processible tetrafluoroethylene 35 copolymer fc awod by heat and/or co",pr~ssion or simple fusion bonding of the walls. Ultrasonic welding may also be used. Other l-letllods of sealing the end of the container may be accomplished by knotting or crimping. The other end of the container serves as an inlet for the ",alerisls that undergo analysis - 217101~

which can also be subsequently sealed or capped off with a plug of polytetrafluoroethylene or glass wool. Altematively the inlet may be sealed shut after the matrix and analyte have been added wherein the sealing is accomplished by any of the means identified above. A third altemative is that 5 the inlet of the container is not sealed or plugged at all but left open.
Although the preferable shape of the container is tubular, there are no limitations on the shape. Thus the container may also be rectangular, square, or have some other shape as shown in Figures 2, 2a, and 2b. Any walls of the container may be sealed together by any of the means described above.
In practice, several tubular containers made of expanded porous polytetrafluoroethylene were used for holding matrices consisting of contaminated soil that were to undergo themmal desG",tion analysis. The containers had a porosity of about 70%, pore size of about 3.5 ~m. in diameter and had inner diameters of 3mm and outer dia",e~era of 4mm. The empty containers were first preweighed and then filled with the matrix containing the analyte and reweighed. Some containers did not have the second end sealed.
Other containers had both ends sealed. Each filled container was then slipped into a thermal desorption stainless steel tube and placed within the analytical chamber of the test machine (in this case - Perkin Elmer Model ATD400). The machine was then oper~ted in accor~ance with standard operating procedures established by the manufadurer of the analytical equipment. The equipment ran at about 200C with no conta",inating inte, rerence from any of the tubular containers. Data of the analyte was obtained from the mass spedo",eter readout. After analysis was complete, the stainless steel tubes were removed from the cha",ber and the expanded porous PTFE tubular containers with the residual matrix of soil were easily removed from the stainless steel tubes and .lis~,ded. Although not required, the stainless steel tubes were cleaned for the next analysis.
AltemaUvely, the containers were used to hold ",onoi"ers and o'.gomera that were analyzed according to the procedures described above. Here the containers were particularly useful as the ",ono")e,a and oligomers were extremely messy and viscous. If stainless steel tubes had been used by themselves, subalan~ial cleaning of the stainless steel tubes after use due to the heavy residual buildup would have been required.
Although the procedures described above require that the containers be used in a test environmént of about 200C, the containers are suitable for use in env;,unn,enta up to about 325C for 5 minutes without any difficulty.
Expanded porous PTFE containers may easily be removed from stainless 217101~

steel tubes at this temperature after use. At higher temperatures (in the range from 335C to 355C) the containers do not deteriorate but forceps or other gripping means are required to remove the container from the tube. The container made solely of expanded porous polytetrafluoroethylene should not be used in temperatures above about 360C due to thermal degradation.
The containers are also believed to be particularly useful in supercritical fluid exl,a- lion wherein a matrix with analyte may be contained within the expanded porous polytetrafluoroethylene container which is then exposed to liquid carbon dioxide. The solutes may be exl,dcled for further analysis carbon dioxide gas may be released and the container remains with the residual matrix.
As used herein:
Pore size for the material used in the container was determined by the amount of air pressure required to force liquid from the largest wetted pore of a membrane. A bubble point rating is used to determine when the largest pore yield a bubble; the larger the pore the less pressure required to form the bubble. ASTM:F31~80 was used to determine this parameter.
Porosity (% void space) was determined by density (weight per volume measurei"enls).
Wall thickness was determined by calculating the difference between the measured outer dia,~,eter of the tubular container and the measured inner clia"~eter.

Claims

I CLAIM:

1. A container for use in holding a matrix with an analyte for analysis comprising a housing of expanded porous polytetrafluoroethylene, an inlet at one end of the housing in which the analyte is introduced into the housing, an interior space formed within the housing in which the analyte once introduced is held and at least one sealed end at the opposite end of the housing, wherein the expanded porous polytetrafluoroethylene has pores with an average size of between 0.1 and 2.0 µm in diameter and a porosity of between 10 and 95% and wherein the analysis may be performed at a temperature of no more than about 360°C.

2. A container as described in Claim 1 wherein the housing has a tubular shape.

3. A container as described in Claim 1 wherein the housing has a rectangular shape.

4. A container as described in Claim 1 for use in analysis selected from the group including physical analysis, thermal analysis and extraction.

5. A container as described in Claim 1 wherein the inlet is subsequently sealed.

6. A container as described in Claim 1 wherein the sealed end is accomplished by a sealing means selected from the group including thermal means, ultrasonic means, adhesive means, compression means, knotting and crimping.

7. A container as described in Claim 1 wherein the expanded porous polytetrafluoroethylene has pores with an average size of 3.5 µm in diameter, and a porosity of about 70%.