Liquid chromatograph with electrochemical detector and method

• US 4,511,659 A
• Filed: 02/17/1984
• Issued: 04/16/1985
• Est. Priority Date: 03/04/1983
• Status: Expired due to Term

• Current Assignee: ESA Biosciences, Inc. (Thermo Fisher Scientific Incorporated)
• Original Assignee: Esa S.R.O. (Logisteed Limited)
• Inventors: Matson, Wayne R.
• Primary Examiner(s): Kaplan, G. L.
• Application Number:
  US06/579,401
• Time in Patent Office: 424 Days
• Field of Search: 436/68, 436/111, 436/150, 436/161, 436/175, 422/70, 204/403, 204/406, 204/411, 204/412, 204/1 K, 204/1 T, 73/61.1 C
• US Class Current: 205/780.5
• CPC Class Codes: G01N 27/27 Association of two or more measuring systems or cells, each measuring a different parameter, where the measurement results may be either used independently, the systems or cells being physically associated, or combined to produce a value for a further parameter
• CPC Class Codes: G01N 2800/2821 Alzheimer
• CPC Class Codes: G01N 30/64 Electrical detectors
• CPC Class Codes: G01N 30/8651 Recording, data aquisition, archiving and storage
• CPC Class Codes: G01N 33/6803 General methods of protein analysis not limited to specific proteins or families of proteins
• CPC Class Codes: Y10T 436/173845 Amine and quaternary ammonium
• CPC Class Codes: Y10T 436/25125 Digestion or removing interfering materials

Abstract

An improved apparatus for electrochemically analyzing a sample in solution is described. The apparatus comprises an electrochemical detector comprising a plurality of electrochemically isolated flow cells arranged in series so as to define at least one flow path. Each of the electrochemical flow cells in turn comprises at least one working electrode, at least one reference electrode, and at least one counter electrode. Electrical potentials are applied to the various working electrodes so that the sample solution is cyclically subjected to oxidation and reduction conditions whereby selected substances contained in the sample solution may be electrically screaned or modified prior to detection and measurement on a downstream sensing electrode.

Claims

1. An electrochemical detection apparatus for electrochemically testing a sample containing reversible and irreversible electrochemically active materials in solution, said apparatus comprising:

at least three coulometric electrochemical flow cell, each of said cells having therein at least one working electrode, at least one counter electrode and at least one reference electrode, said plurality of electrochemical cells being arranged in series and defining collectively at least one flow channel for said sample solution;

means for connecting each said reference electrode to a reference potential;

means connecting each said counter electrode to a counter potential; and

means connecting each said working electrode to a working potential, at least two of said cells constituting gate cells, each of said gate cells having means for maintaining its working electrode at a different potential from the other, one of said gate cells being at a potential to oxidize electrochemcially active materials in said sample and another of said gate cells being at a potential to reduce electrochemically active materials in said sample

said remaining cell or cells having means for maintaining its working electrode at a potential to detect and coulometrically measure electrochemically reversible materials in said sample.

2. In an apparatus for analyzing complex mixtures of electrochemically active fluids such as blood, cerebrospinal fluids and the like containing electrochemically irreversible materials and trace quantities of electrochemically reversible materials, comprising a liquid chromatographic column for achieving time spaced separation of the materials eluting from the column and an electrochemical detection apparatus for electrochemically testing a sample containing reversible and irreversible electrochemically active materials in solution, the improvement wherein said detection apparatus comprises

at least three coulometric electrochemical flow cells, each of said cells having therein at least one working electrode, at least one counter electrode and at least one reference electrode, said plurality of electrochemical cells being arranged in series and defining collectively at least one flow channel for said sample solution;

means for connecting each said reference electrode to a reference potential;

means connecting each said counter electrode to a counter potential; and

means connecting each said working electrodes to a working potential, at least two of said cells constituting gate cells, each of said gate cells having means for maintaining its working electrode at a different potential from the other, one of said gate cells being at a potential to oxidize electrochemically active materials in said sample and another of said gate cells being at a potential to reduce electrochemically active materials in said sample

said remaining cell or cells having means for maintaining its working electrode at a potential to detect and coulometrically measure electrochemically reversible materials in said sample.

3. The apparatus of claim 2 wherein said detection apparatus includes at least two measuring cells following said gate cells, the working electrodes of said measuring cells being at different potentials to provide different electrochemical measurements for electrochemically active species passing sequentially through said two measuring cells.

4. The apparatus of claim 3 wherein said two measuring cells operate at progressively varying potentials along said flow path.

5. The apparatus of claim 4 wherein means are provided for displaying said measurements so as to separate said measurements by measuring potential as well as by time of elution.

6. The apparatus of claim 5 wherein the measuring cells are sufficiently close along said channel that time of transit of eluant between measuring cells is insignificant with respect to overall elution times.

7. The apparatus of claim 2 wherein the working electrode in each gate cell has an area equal to at least 50 half times, the area of the working electrode in the detection cell being less than 1/10 that of the preceding gate cell working electrode.

8. In apparatus for analyzing complex mixtures of electrochemically active fluids such as blood, cerebrospinal fluids and the like containing electrochemically irreversible materials and trace quantities of electrochemically materials, comprising a liquid chromatographic column for achieving time spaced separation of the materials eluting from the column and an electrochemical detection apparatus for electrochemically testing a sample containing reversible and irreversible electrochemically active materials in solution, the improvement wherein said detection apparatus comprises

at least two gate cells arranged to change the oxidation state of electrochemically reversible and electrochemically irreversible materials and convert at least some of said materials to an electrochemically inactive state at the potential on a following coulometric measuring electrode, at least one additional test cell following said two gate cells, arranged to coulometrically measure electrochemically reversible materials of interest in the eluant at a measuring electrode held at a potential adequate to detect and measure the quantity of said materials of interest.

9. The apparatus of claim 8 wherein said oxidizing gate cell precedes said reducing gate cell.

10. The apparatus of claim 8 wherein said reducing gate cell precedes said oxidizing gate cell.

11. The apparatus of claim 8 wherein said measuring cell reduces said electrochemically reversible species.

12. The apparatus of claim 8 wherein said measuring cell oxidizes said electrochemically reversible species.

13. The method for analyzing complex mixtures of electrochemically active fluids containing electrochemically irreversible materials and trace quantities of electrochemically reversible materials comprising the steps of passing said electrochemically active fluids sequentially through a liquid chromatographic column for achieving time spaced separation of the materials eluting from the column and an electrochemical detection apparatus for electrochemically testing a sample containing reversible and irreversible electrochemically active materials in solution, the detection apparatus comprising at least three coulometric cells arranged in series, maintaining the coulometric electrodes of two of said cells at different potentials to change the oxidation state of electrochemically reversible and electrochemically irreversible materials and convert at least some of said materials to an electrochemically inactive state at the potential maintained on a following coulometric measuring electrode, providing at least one additional test cell following said two gate cells, and coulometrically measuring electrochemically reversible materials of interest in the eluant at a measuring electrode held at a potential adequate to detect and measure the quantity of said materials of interest.

14. The method of claim 13 wherein said detection apparatus includes at least two measuring cells following said gate cells, the working electrodes of said measuring cells being at different potentials to provide different electrochemical measurements for electrochemically active species passing sequentially through said two measuring cells.

15. The method of claim 14 wherein said two measuring cells operate at progressively varying potentials along said flow path.

16. The method of claim 15 including the additional step of displaying said measurements so as to separate said measurements by measuring potential as well as by time of elution.

17. The method of claim 14 wherein the measuring cells are sufficiently close along said channel that time of transit of eluant between measuring cells is insignificant with respect to overall elution times.

18. The method of claim 13 wherein said electrochemically active fluid comprises blood.

19. The method of claim 13 wherein said electrochemically active fluid comprises cerebrospinal fluid.

20. The method for analyzing complex mixtures of electrochemically active fluids containing electrochemically irreversible materials and trace quantities of electrochemically reversible materials comprising the steps of passing said electrochemically active fluids sequentially through a liquid chromatographic column for achieving time spaced separation of the materials eluting from the column and an electrochemical detection apparatus for electrochemically testing a sample containing reversible and irreversible electrochemically active materials in solution, the detection apparatus comprising at least three coulometric cells arranged in series, maintaining the coulometric electrodes of two of said cells at different potentials to change the oxidation state of electrochemically reversible and electrochemically irreversible materials and convert at least some of said materials to an electrochemically inactive state at the potential maintained on a following coulometric measuring electrode, providing at least one additional test cell following said two gate cells and coulometrically measuring electrochemically reversible materials of interest in the eluant at a measuring electrode held at a potential adequate to detect and measure the quantity of said materials of interest, connecting each said working electrodes to a working potential, at least two of said cells constituting gate cells, each of said gate cells having its working electrode at a different potential from the other, one of said gate cells being at a potential to oxidize electrochemically active materials in said sample and another of said gate cells being at a potential to reduce electrochemically active materials in said sample

said remaining cell or cells having its working electrode at a potential to detect and coulometrically measure electrochemically reversible materials in said sample.

21. The method of claim 20 wherein said oxidizing gate cell precedes said reducing gate cell.

22. The method of claim 20 wherein said reducing gate cell precedes said oxidizing gate cell.

23. The method of claim 20 wherein said measuring cell reduces said electrochemically reversible species.

24. The method of claim 20 wherein said measuring cell oxidizes said electrochemically reversible species.

25. The method of claim 20 wherein said electrochemically active fluid comprises blood.

26. The method of claim 20 wherein said electrochemically active fluid comprises cerebrospinal fluid.