Analysis of volatile organic compounds

• US 4,003,257 A
• Filed: 03/12/1974
• Issued: 01/18/1977
• Est. Priority Date: 03/12/1974
• Status: Expired due to Term

• Current Assignee: Albert Zlatkis, Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of
• Original Assignee: Albert Zlatkis, Fletcher James C Administrator of The National Aeronautics and Space Administration With Respect To An Invention of
• Inventors: Fletcher, James C. Administrator of the National Aeronautics and Space Administration, with respect to an invention of, Zlatkis, Albert
• Primary Examiner(s): Yudkoff, Norman
• Assistant Examiner(s): Hollander, Barry I.
• Application Number:
  US05/450,504
• Time in Patent Office: 1,043 Days
• Field of Search: 23/230 R, 23/230 B, 23/230 M, 23/232 R, 23/232 C, 23/254 R, 23/231, 73/23.1, 73/61.1 C, 55/197, 55/67, 55/74
• US Class Current: 73/19.02
• CPC Class Codes: G01N 2001/2229 Headspace sampling, i.e. vapour over liquid
• CPC Class Codes: G01N 30/06 Preparation
• CPC Class Codes: Y10T 436/21 Hydrocarbon
• CPC Class Codes: Y10T 436/255 including use of a solid sorbent, semipermeable membrane, or liquid extraction

Abstract

System and method for reproducibly analyzing, both qualitatively and quantitatively, trace amounts of a large number of organic volatiles existing in a gas sample. Applications include (1) analyzing the headspace gas of body fluids and comparing a profile of the oganic volatiles with standard profiles for the detection and monitoring of disease, (2) analyzing the headspace gas of foods and beverages and comparing a profile of the organic volatiles with standard profiles so that flavor and aroma can be monitored and controlled, and (3) similar analysis for determining the organic pollutants in samples of water and air.

The system includes a novel means (sample trap) for capturing and enriching the organic volatiles, a novel injector port for directly injecting the entrapped organic volatiles to a cryogenic percolumn to provide a sharply defined plug, and a novel capillary separating column. Various detectors may be utilized to identify the separated volatiles.

The sample trap contains a solid adsorbent having the following properties: (1) high affinity for volatile organic compounds, (2) hydrophobic, (3) temperature stability up to 400° C, (4) good desorption capability and (5) relative inertness to the sample. A porous material based on a polymer of 2,6-diphenyl-p-phenylene oxide (PPPO) and sold under the trademark TENAX-GC is particularly suited for this purpose. The injector port is formed of a hollow body having inlet and outlet ports. The sample trap is inserted into the body and maintained in sealed engagement with the outlet port. The injector port is placed into an injector heater of a gas chromatograph (GC) to effect desorption of the entrapped volatiles. Helium gas is introduced at the inlet port to carry the organic volatiles directly into the cryogenic precolumn. The GC capillary separating column is formed of etched nickel which facilitates the separation of a large number of specific organic compounds from a very small amount of organic volatiles.

Claims

1. In a method of analysis in a gas chromatographic system for volatile organic compounds in a sample, the step of

remotely and independently of the gas chromatographic system trapping the volatile organic compounds in the sample by adsorbing them on a porous polymer consisting essentially of 2,6-diphenyl-p-phenylene oxide, said polymer having properties of high affinity for organic volatiles being hydrophobic, having temperature stability up to about 400°

C., having good desorptivity, and being relatively inert to the sample, whereby such trapped volatile organic compounds are retained;

for later chromatographic analysis.

2. The method of claim 1 where, the sample is selected from the group consisting of body fluids and tissue culture.

3. The method of claim 1 where, the sample is air.

4. The method of claim 1 where, the sample is water.

5. The method of claim 1 where, the sample is selected from the group consisting of food and drink.

6. The method of claim 1 where, the sample is smoke.

7. The method of claim 1 further comprising the steps of:

subsequent desorbing, without artifacts, the adsorbed volatile organic compounds from the porous polymer at temperatures from ambient up to about 400°

c.,

collecting the desorbed volatile organic compounds, and,

chromatographic analyzing of the volatile organic compounds.

8. The method of claim 7 where, the analyzing is by obtaining a profile of the desorbed volatile organic compounds and comparing the profile of the desorbed volatile organic compounds with a profile of volatile organic compounds from a reference.

9. The method of claim 8 where, the sample is selected from the group consisting of body fluids and tissue culture.

10. The method of claim 8 where, the sample is air.

11. The method of claim 8 where, the sample is water.

12. The method of claim 8 where, the sample is smoke.

13. The method of claim 8 where, the sample is selected from the group consisting of food and drink.

14. The method of claim 8 where, the sample and the reference are selected from the group consisting of body fluids and tissue culture.

15. The method of claim 8 where, the sample and the reference are smoke.

16. The method of claim 8 where, the sample and the reference are air.

17. The method of claim 8 where, the sample and the reference are water.

18. The method of claim 8 where, the sample and the reference are selected from the group consisting of food and drink.

19. The method of claim 14 where the desorbing is at temperatures from about 230°

C. up to about 400°

C.,

a profile of the desorbed volatile organic compounds is obtained, and

the profile is compared with a profile of volatile organic compounds from a reference sample.

20. The method of claim 19 where, the desorbing is at temperatures from about 230°

C. to about 300°

C.

21. The method of claim 20 where, the sample and the reference sample are selected from the group consisting of blood plasma and blood serum.

22. The method of claim 20 where, the sample and the reference sample are urine.

23. The method of claim 8 where the volatile organic compounds are from the headspace between a sample of a processed product and the adsorbent.

24. The method of claim 8 where the volatile organic compounds are from the headspace between a sample selected from the group consisting of body fluids and tissue culture and the adsorbent.

25. The method of claim 1 where, the adsorbing of the volatile organic compounds on the polymer is at temperatures from ambient room temperature and below.

26. The method of claim 1, wherein the polymer is encased in a supportive tube like body.

27. The method of claim 26 wherein the tube like body after adsorption of the volatile organic compounds is enclosed is a sealable container for transportation or storage.

28. A method of analyzing volatile organic compounds in a sample comprising,

trapping the volatile organic compounds by adsorbing them on a porous polymer consisting essentially of 2,6-diphenyl-p-phenylene oxide in a trap,

connecting the trap to a cryogenically cooled precolumn of a gas chromatograph thermally desorbing without artifacts the adsorbed volatile organic compounds from the polymer in the trap, and transferring them to the precolumn and,

transferring the volatile organic compounds from the precolumn to a separating column of the gas chromatograph for analysis.

29. The method of claim 28 where, the separating column is a thin-walled capillary tube formed of nickel etched with a solution of concentrated nitric and acetic acids.

30. The method of claim 28 where, the desorbing of the volatile organic compounds to the precolumn is by heating the porous polymer to temperatures up to about 400°

C.

31. The method of claim 30 where, the sample is selected from the group consisting of body fluids and tissue culture.

32. The method of claim 30 where, the sample is air.

33. The method of claim 30 where, the sample is water.

34. The method of claim 30 where, the sample is selected from the group consisting of food and drink.

35. The method of claim 30 where, the sample is smoke.

36. The method of claim 28 where, the desorbing of the volatile organic compounds is by heating the porous polymer to temperatures up to about 400°

C.