Gated Amperometry

• US 20080173552A1
• Filed: 12/19/2007
• Published: 07/24/2008
• Est. Priority Date: 07/20/2005
• Status: Active Grant

• Current Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Original Assignee: Bayer Healthcare LLC (Bayer AG)
• Inventors: Wu, Huan-Ping, Nelson, Christine D., Beer, Greg P.
• Granted Patent: US 8,425,757 B2
• Time in Patent Office: Days
• US Class Current: 205/775
• CPC Class Codes: A61B 2562/0295 Strip shaped analyte sensors for apparatus classified in A61B5/145 or A61B5/157
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: C12Q 1/26 involving oxidoreductase
• CPC Class Codes: G01N 27/26 by investigating electrochemical variables; by using electrolysis or electrophoresis
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875

Abstract

A sensor system, device, and methods for determining the concentration of an analyte in a sample is described. Gated amperometric pulse sequences including multiple duty cycles of sequential excitations and relaxations may provide a shorter analysis time and/or improve the accuracy and/or precision of the analysis. The disclosed gated amperometric pulse sequences may reduce analysis errors arising from the hematocrit effect, variance in cap-gap volumes, non-steady-state conditions, mediator background, under-fill, temperature changes in the sample, and a single set of calibration constants.

Claims

1. A method for determining the concentration of an analyte in a sample, comprising:

applying an input signal to the sample, the input signal comprising at least 3 duty cycles within 180 seconds and each duty cycle comprising an excitation and relaxation;

measuring an output signal responsive to a measurable species; and

determining the concentration of the analyte in the sample in response to the measured output signal.

2. The method of claim 1, further comprising introducing the sample to a sensor strip and transferring at least one electron from the analyte in the sample to a mediator in the sensor strip, where the input signal electrochemically excites the measurable species, and the measurable species is selected from the group consisting of the analyte, the mediator, and combinations thereof.

3. The method of claim 1, where the excitation has a substantially constant voltage.

5. The method of claim 1, where the input signal comprises square-wave excitations.

6. The method of claim 1, where the input signal has a redox intensity of at least 0.01.

7. The method of claim 1, where the concentration of the analyte determined from the method includes less bias attributable to mediator background than a concentration of the analyte determined from the same or another method lacking the input signal comprising at least 3 duty cycles within 180 seconds.

8. The method of claim 1, further comprising recording at least one current as a function of time during the application of the input signal.

9. The method of claim 1, where the determining comprises applying at least one data treatment to at least one current of the output signal.

10. The method of claim 1, further comprising:

exciting the measurable species internal to a diffusion barrier layer; and

substantially excluding from excitation the measurable species external to the diffusion barrier layer.

4. (canceled)

11. (canceled)

12. (canceled)

13. The method of claim 12, where the excitation is less than 5 seconds.

15. The method of claim 12, where the relaxation is at least 0.5 seconds.

16. The method of claim 12, where the current profile includes a transient decay and the analyte concentration is determined from the transient decay.

14. (canceled)

17. (canceled)

18. The method of claim 17, further comprising determining the number of duty cycles in the input signal in response to the multiple sets of calibration constants.

19-23. -23. (canceled)

24. A handheld measuring device, for determining the concentration of an analyte in a sample, where

the device is adapted to receive a sensor strip and the device comprises:

contacts;

at least one display; and

electronic circuitry establishing electrical communication between the contacts and the display, the circuitry comprising;

an electric charger and a processor in electrical communication, the processor in electrical communication with a computer readable storage medium comprising computer readable software code, which when executed by the processor, causes the charger to implement an input signal comprising at least 3 duty cycles within 180 seconds between the contacts, each duty cycle comprising an excitation and a relaxation.

25. The device of claim 24, where the excitation is at a substantially constant voltage.

26. The device of claim 24, where the processor is operable to measure at least one current profile at the contacts and to determine the analyte concentration of the analyte in the sample in response to the at least one current profile.

27. A method of reducing the bias attributable to mediator background in a determined concentration of an analyte in a sample comprising:

applying an input signal to the sample, the input signal comprising at least 3 duty cycles within 180 seconds.

28. A method of signaling a user to add additional sample to a sensor strip, comprising:

determining if the sensor strip is under-filled by determining a decay constant from currents recorded during at least two excitations of an input signal including at least 3 duty cycles within 180 seconds; and

signaling the user to add additional sample to the sensor strip if the strip is under-filled.

29. A method of determining the temperature of a sample contained by a sensor strip, comprising:

determining a decay constant from currents recorded during at least two excitations of an input signal including at least 3 duty cycles within 180 seconds; and

correlating the decay constant with a temperature value.

30. A method of determining the duration of an input signal including at least 3 duty cycles within 180 seconds, for determining the concentration of an analyte in a sample comprising:

determining a plurality of calibration points determined from currents recorded during the at least 3 duty cycles; and

determining the duration of the input signal in response to the determined concentration of the analyte in the sample.