Method and apparatus for analyzing volatile chemical components in a liquid

• US 5,235,843 A
• Filed: 01/16/1991
• Issued: 08/17/1993
• Est. Priority Date: 08/24/1988
• Status: Expired due to Fees

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Langhorst, Marsha L.
• Primary Examiner(s): MYRACLE, JERRY
• Application Number:
  US07/641,992
• Time in Patent Office: 944 Days
• Field of Search: 73/23.35, 73/19.02, 73/19.12, 73/61.44, 73/864.81, 73/19.1, 55/53, 55/196, 55/197
• US Class Current: 73/19.02
• CPC Class Codes: G01N 1/34 Purifying; Cleaning processes or apparatus for extracting or separating nucleic acids from biological samples C12N15/1003
• CPC Class Codes: G01N 2001/2229 Headspace sampling, i.e. vapour over liquid
• CPC Class Codes: G01N 2001/4016 being a selective membrane, e.g. dialysis or osmosis
• CPC Class Codes: G01N 2030/065 using different phases to separate parts of sample
• CPC Class Codes: G01N 30/06 Preparation
• CPC Class Codes: G01N 33/0049 Halogenated organic compounds

Abstract

A sample of a volatile chemical component-containing liquid is segmented in stream flow with a gas with the volatile components partitioning or separating into the two phases, the gas then being separated from the stream and the volatile components therein analyzed for identification and concentration.

Claims

1. A method of analyzing a first fluid for the presence therein of at least one volatile compound, said method comprising:

(a) establishing a unidirectional, confined, flowing stream of segments of said first fluid separated by segments of a second fluid into which said compound is partitionable;

(b) maintaining said stream flowing for a distance sufficient to enable partitioning of said compound from the segments of said first fluid into the segments of said second fluid;

(c) separating the segments of said first and second fluids; and

(d) analyzing the separated segments of said second fluid for determining the content therein of said compound.

2. The method of claim 1 wherein the segments of said first fluid are liquid and the segments of said second fluid are gas.

3. The method of claim 2 including dehumidifying the separated gas segments prior to the analysis thereof.

4. The method of claim 3 including separating the gas segments from the liquid segments via a membrane phase separator.

5. The method of claim 4 including analyzing the separated gas segments via gas chromatography.

6. The method of claim 3 including transferring the volatile compound of the liquid segments to the gas segments primarily during the flowing of said stream.

7. The method of claim 2 including analyzing the separated gas segments via gas chromatography.

8. The method of claim 7 wherein the compound detected is divided by its respective enrichment factor to determine the concentration thereof in said liquid segments.

9. The method of claim 8 wherein said enrichment factor is within the range of from 1 to 100.

10. The method of claim 8 wherein said enrichment factor is within the range of 1.7 to 76.

11. The method of claim 2 including transferring the volatile compounds of the liquid segments to the gas segments primarily during the flowing of said stream.

12. The method of claim 11 including analyzing the separated gas segments via gas chromatography.

13. The method of claim 2 including separating the gas segments from the liquid segments by debubbling said stream.

14. The method of claim 2 including separating the gas segments from the liquid segments via a membrane phase separator.

15. The method of claim 14 wherein the membrane phase separator is formed from microporous polypropylene.

16. The method of claim 2 including dehumidifying the separated gas segments prior to their analysis.

17. The method of claim 16 wherein the dehumidification of the separated gas segments includes removing water vapor from the gas segments by transferring the water vapor through a microporous membrane formed from a product of perfluorosulfonic acid.

18. The method of claim 2 including subjecting the separated gas segments to flow-through purging action.

19. The method of claim 2 wherein separating said liquid and gas segments includes flowing the stream of gas and liquid segments into a chamber having an upper gas outlet and a lower liquid trap, collecting and draining the liquid from liquid segments through the trap while forming a headsapce above the liquid in the chamber, and collecting the gas in the headspace.

20. The method of claim 2 wherein said analyzing step includes analyzing the separated gas segments by microchip gas chromatography.

21. Apparatus for the analysis of volatile compounds in a first fluid, said apparatus comprising:

(a) partitioning means for establishing a flowing stream composed of segments of the first fluid spaced by segments of a second fluid which partition the volatile compounds into the second fluid from the first fluid;

(b) separating means for separating the segments of the second fluid from said stream;

(c) analyzing means for analyzing said separated segments of the second fluid to identify volatile compounds therein, and

d) means for delivering said separated segments of the second fluid to said analyzing means.

22. The apparatus of claim 21 wherein said separating means includes a hollow microporous fiber.

23. The apparatus of claim 22 wherein said fiber is formed of polytetrafluoroethylene.

24. The apparatus of claim 22 wherein said separating means includes a second microporous hollow fiber accommodated within the first mentioned fiber.

25. The apparatus of claim 24 wherein said second fiber is formed of a perfluorosulfonic acid product.

26. The apparatus of claim 24 wherein the first fluid is a liquid and the second fluid is a gas, said fibers extending through a separation chamber, said first mentioned fiber being in communication with stream input means and liquid discharge means;

and sampling port means establishing communication between said chamber and the interior of said second fiber.

27. The apparatus of claim 21 wherein said separating means includes a film of microporous polypropylene.

28. The apparatus of claim 21 wherein said partitioning means for establishing said flowing stream includes a peristaltic pump.

29. The apparatus of claim 21 wherein the first fluid is a liquid and the second fluid is a gas, said apparatus further including dehumidifying means acting on said separated gas segments prior to analysis thereof.

30. The apparatus of claim 21 wherein the first fluid is a liquid and the second fluid is a gas, said analyzing means comprising a gas chromatograph.

31. The apparatus of claim 30 wherein said gas chromatograph is a microchip gas chromatography system.

32. The apparatus of claim 31 wherein said separating means is formed of microporous polytetrafluoroethylene.

33. The apparatus of claim 21 including flow-through purging means.

34. The apparatus of claim 21 wherein said separating means is formed of microporous polypropylene.

35. The apparatus of claim 21 wherein said separating means is formed partly of microporous polypropylene and partly of microporous polytetrafluoroethylene.

36. The apparatus of claim 21 wherein the first fluid is a liquid and the second fluid is a gas, said separating means including a chamber having an upper gas outlet and a lower liquid trap, the liquid trapped in the chamber forming a headspace thereabove within the chamber for collecting the gas therein.

37. The apparatus of claim 36 wherein said chamber includes a gas outlet from said headspace to an outer environment, said apparatus including pumping means for continually pumping the liquid and gas segments through said system, said lower liquid trap and said gas outlet allowing for continued exhaust of liquid and gas for continual real time analysis of subsequent segments flowing under positive pressure from said pumping means to said chamber.