Liquid chromatograph with electrochemical detector and method
First Claim
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 samplesaid 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.
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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.
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Citations
26 Claims
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1. An electrochemical detection apparatus for electrochemically testing a sample containing reversible and irreversible electrochemically active materials in solution, said apparatus comprising:
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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.
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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. - View Dependent Claims (3, 4, 5, 6, 7)
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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.
- 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.
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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.
Specification