Method and apparatus for compensating for drift in potential of a reference electrode in electrochemical measurements
First Claim
1. A method for making an electrochemical measurement of a concentration of at least one chemical entity dissolved in a liquid medium, comprising the steps of:
- immersing only a counter electrode, a working electrode and a reference electrode in a liquid medium in which at least one chemical entity is dissolved;
applying a measurement potential to the working electrode relative to the reference electrode, corresponding to a measurement voltage during at least a portion of a measurement period, and thereby causing said chemical entity to participate in an electrochemical reaction at the working electrode, said electrochemical reaction resulting in a measurement evoked current;
measuring said measurement evoked current;
comparing said measurement evoked current with a predetermined value; and
compensating for potential drift at said reference electrode by changing said measurement voltage in incremental steps to cause said measurement current to approach said predetermined value, and after each increment of said measurement voltage, comparing a resulting measurement evoked current with said predetermined value, and continuing incrementally changing said measurement potential until said measurement evoked current is substantially equal to said predetermined value.
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Abstract
In a method and an apparatus for measuring a concentration of at least one dissolved chemical entity in a liquid medium, employing a counter electrode, a working electrode and a reference electrode immersed in the liquid medium, at least one measurement potential is applied to the working electrode relative to the reference electrode, corresponding to a measurement voltage during at least a part of a measurement period, thereby causing the dissolved chemical entity to participate in an electrochemical reaction at the working electrode, the chemical reaction resulting in a measurement evoked current. Compensation for potential drift at the reference electrode is achieved by comparing the measurement evoked current with a predetermined value, and decreasing or increasing the measurement voltage by an incremental value, in a negative or a positive incremental step, so that the measurement current approaches a predetermined value. After each increment, a new comparison is made and the next increment is determined dependent on that most recent comparison.
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Citations
9 Claims
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1. A method for making an electrochemical measurement of a concentration of at least one chemical entity dissolved in a liquid medium, comprising the steps of:
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immersing only a counter electrode, a working electrode and a reference electrode in a liquid medium in which at least one chemical entity is dissolved;
applying a measurement potential to the working electrode relative to the reference electrode, corresponding to a measurement voltage during at least a portion of a measurement period, and thereby causing said chemical entity to participate in an electrochemical reaction at the working electrode, said electrochemical reaction resulting in a measurement evoked current;
measuring said measurement evoked current;
comparing said measurement evoked current with a predetermined value; and
compensating for potential drift at said reference electrode by changing said measurement voltage in incremental steps to cause said measurement current to approach said predetermined value, and after each increment of said measurement voltage, comparing a resulting measurement evoked current with said predetermined value, and continuing incrementally changing said measurement potential until said measurement evoked current is substantially equal to said predetermined value. - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for making an electrochemical measurement of a concentration of at least one chemical entity dissolved in a liquid medium, comprising:
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only a counter electrode, a working electrode and a reference electrode immersed in a liquid medium in which at least one chemical entity is dissolved;
a potentiostat for applying a measurement potential to the working electrode relative to the reference electrode, corresponding to a measurement voltage during at least a portion of measurement period, and thereby causing said chemical entity to participate in an electrochemical reaction at the working electrode, said electrochemical reaction resulting in a measurement evoked current;
a measuring unit for said measurement evoked current;
a comparator for comparing said measurement evoked current with a predetermined value to obtain a comparison result; and
said potentiostat compensating for potential drift at said reference electrode by changing said measurement voltage in incremental steps to cause said measurement current to approach said predetermined value, and after each increment of said measurement voltage, said comparator comparing a resulting measurement evoked current with said predetermined value and supplying said comparison result to said potentiostat, and said potentiostat continuing to incrementally change said measurement potential until said measurement evoked current is substantially equal to said predetermined value. - View Dependent Claims (7, 8, 9)
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Specification