Method and apparatus for assay of electrochemical properties
First Claim
1. A method of evaluating a sample for the presence of a select analyte comprising the steps of:
- (a) introducing the sample into a space between two electrodes of a conduction cell;
(b) applying a potential or current between the two electrodes sufficient to bring about oxidation or reduction of the analyte or of a mediator in an analyte-detection redox system, thereby forming a chemical potential gradient of the analyte or mediator between the two electrodes;
(c) after the gradient is established, discontinuing the applied potential or current and obtaining an analyte-independent signal reflecting relaxation of the chemical potential gradient;
(d) optionally applying a potential or current between the electrodes after the analyte-independent signal is obtained;
(e) obtaining an analyte-dependent signal during the application of the potential or current in step (b) or step (d) or both, and(f) correcting the analyte-dependent signal obtained in step (e) using the analyte-independent signal obtained in step (c) to obtain a corrected analyte-dependent signal indicative of the presence of the selected analyte in the sample.
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Abstract
The presence of a select analyte in the sample is evaluated in an an electrochemical system using a conduction cell-type apparatus. A potential or current is generated between the two electrodes of the cell sufficient to bring about oxidation or reduction of the analyte or of a mediator in an analyte-detection redox system, thereby forming a chemical potential gradient of the analyte or mediator between the two electrodes After the gradient is established, the applied potential or current is discontinued and an analyte-independent signal is obtained from the relaxation of the chemical potential gradient. The analyte-independent signal is used to correct the analyte-dependent signal obtained during application of the potential or current. This correction allows an improved measurement of analyte concentration because it corrects for device-specific and test specific factors such as transport (mobility) of analyte and/or mediator, effective electrode area, and electrode spacing (and as a result, sample volume), without need for separate calibration values. The analysis can be performed using disposable test strips in a hand held meter, for example for glucose testing.
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Citations
22 Claims
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1. A method of evaluating a sample for the presence of a select analyte comprising the steps of:
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(a) introducing the sample into a space between two electrodes of a conduction cell; (b) applying a potential or current between the two electrodes sufficient to bring about oxidation or reduction of the analyte or of a mediator in an analyte-detection redox system, thereby forming a chemical potential gradient of the analyte or mediator between the two electrodes; (c) after the gradient is established, discontinuing the applied potential or current and obtaining an analyte-independent signal reflecting relaxation of the chemical potential gradient; (d) optionally applying a potential or current between the electrodes after the analyte-independent signal is obtained; (e) obtaining an analyte-dependent signal during the application of the potential or current in step (b) or step (d) or both, and (f) correcting the analyte-dependent signal obtained in step (e) using the analyte-independent signal obtained in step (c) to obtain a corrected analyte-dependent signal indicative of the presence of the selected analyte in the sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for determining the effective separation distance between a first electrode and a second electrode in an electrochemical cell, the method comprising the steps of:
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applying an external force in the form of an applied potential or an applied current to generate a chemical potential gradient between the first electrode and the second electrode; stopping the application of the external force; observing the decay of the chemical potential gradient as a function of time; and computing the effective electrode separation distance from the observed decay of the chemical potential gradient.
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17. A method for determining an effective transport property between a first electrode and a second electrode in an electrochemical cell, the method comprising the steps of:
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applying an external force in the form of an applied potential or a current to generate a chemical potential gradient between the first electrode and the second electrode; stopping the application of the external force; observing the decay of the chemical potential gradient as a function of time; and computing an effective transport property of the electrochemical system from the observed decay of the chemical potential gradient.
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18. An apparatus for determining the presence of an analyte in a sample disposed in an electrochemical cell said electrochemical cell comprising two electrodes between which the sample is placed for analysis, said apparatus comprising:
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(a) a housing having a space for receiving the electrochemical cell; (b) means for applying a potential or a current between the two electrodes of the electrochemical cell when it is received within the housing; (c) means for measuring oxidation or reduction of an analyte or a mediator in an analyte-detection system occurring within the electrochemical cell when the potential or current is being applied; (d) means for switching the potential or current off after a period of time during which a chemical potential gradient is established between the two electrodes; (e) means for monitoring the decay of the chemical potential gradient after the potential or current is switched off; (f) programmed data processing means for combining the measured oxidation or reduction with the monitored decay to produce an indication of the presence of the analyte in the sample; and (g) output means for conveying the indication of the presence of the analyte in the sample to a user. - View Dependent Claims (19, 20, 21, 22)
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Specification