Method for measuring an analyte in a sample
A sensor system including devices and methods for determining the concentration of an analyte in a sample is described. Input signals including amperometric and voltammetric duty cycles of excitations and relaxations may provide a shorter analysis time and/or improve the accuracy and/or precision of the analysis. The disclosed system may reduce analysis errors, thus improving measurement performance, by adjusting the potential and/or scan rate in response to output currents obtained from voltammetric scans. The disclosed system also may determine the concentration of more than one ionizable species in the sample by adjusting the potential and/or scan rate in response to output currents obtained from voltammetric scans. The multiple, determined concentrations may be used to determine the concentration of multiple analytes or to correct the concentration determined for an analyte, thus improving the measurement performance of the system.
1. A method for measuring an analyte in a sample comprising:
applying to the sample an input signal comprising:
a first duty cycle including an amperometric excitation and a first relaxation; and
a second duty cycle including a voltammetric excitation and a second relaxation;
detecting an output signal comprising:
amperometric output currents responsive to the amperometric excitation; and
voltammetric output currents responsive to the voltammetric excitation;
adjusting a voltammetric scan rate of the voltammetric excitation in response to the voltammetric output currents; and
correlating a portion of the output signal with a concentration of at least one analyte in the sample.
2. The method of claim 1 , further comprising adjusting a potential of the amperometric excitation in response to the voltammetric output currents.
3. The method of claim 1 , comprising correlating a portion of the output signal including at least one amperometric output current of the amperometric output currents with the concentration of the at least one analyte in the sample.
4. The method of claim 1 , wherein the input signal further includes a third duty cycle having an acyclic scan and a third relaxation, and the method further comprises:
adjusting a potential of the acyclic scan of the third duty cycle in response to the voltammetric output currents.
5. The method of claim 4 , further comprising correlating a portion of the output signal including at least one output current responsive to the acyclic scan of the third duty cycle with the concentration of the at least one analyte in the sample.
6. The method of claim 4 , wherein the adjusting of the potential reduces output currents responsive to a second contributing ionizable species in relation to output currents responsive to a first contributing ionizable species in the output signal.
7. The method of claim 6 , further comprising correlating a portion of the output signal including at least one output current responsive to the first contributing ionizable species with the concentration of the at least one analyte in the sample.
8. The method of claim 1 , wherein the input signal further includes a third duty cycle having an acyclic scan and a third relaxation, and the method further comprises:
adjusting a potential of the amperometric excitation in response to the voltammetric output currents, a potential of the acyclic scan in response to the voltammetric output currents, or a combination thereof,
wherein the adjusting reduces output currents responsive to a second contributing ionizable species in relation to output currents responsive to a first contributing ionizable species in the output signal.
9. The method of claim 8 , further comprising comparing a portion of the output signal including at least one output current responsive to the first contributing ionizable species with a portion of the output signal including at least one output current responsive to the second contributing ionizable species to provide a concentration of the second contributing ionizable species.
10. The method of claim 1 , further comprising comparing a portion of the output signal including at least one output current responsive to a first contributing ionizable species with a portion of the output signal including at least one output current responsive to a second contributing ionizable species to provide a concentration of the second contributing ionizable species.
11. The method of claim 10 , wherein the second contributing ionizable species is an interferent.
12. The method of claim 1 , wherein the voltammetric excitation of the second duty cycle is a linear scan.
13. The method of claim 1 , wherein the voltammetric excitation of the second duty cycle is an acyclic scan having a forward excitation and a reverse excitation.
14. A method for measuring an analyte in a sample comprising:
applying to the sample an input signal comprising:
a first duty cycle including an amperometric excitation and a first relaxation; and
a second duty cycle including a voltammetric excitation and a second relaxation;
detecting an output signal comprising:
amperometric output currents responsive to the amperometric excitation; and
voltammetric output currents responsive to the voltammetric excitation; and
correlating a portion of the output signal with a concentration of at least one analyte in the sample,
wherein the voltammetric excitation of the second duty cycle is (1) a linear scan or (2) an acyclic scan having a forward excitation and a reverse excitation.
15. The method of claim 14 , further comprising adjusting a potential of the amperometric excitation in response to the voltammetric output currents.
16. The method of claim 14 , comprising correlating a portion of the output signal including at least one amperometric output current of the amperometric output currents with the concentration of the at least one analyte in the sample.
17. The method of claim 14 , wherein the input signal further includes a third duty cycle having an acyclic scan and a third relaxation, and the method further comprises:
adjusting a potential of the acyclic scan of the third duty cycle in response to the voltammetric output currents.
18. The method of claim 17 , further comprising correlating a portion of the output signal including at least one output current responsive to the acyclic scan of the third duty cycle with the concentration of the at least one analyte in the sample.
19. The method of claim 17 , wherein the adjusting of the potential reduces output currents responsive to a second contributing ionizable species in relation to output currents responsive to a first contributing ionizable species in the output signal.
20. The method of claim 19 , further comprising correlating a portion of the output signal including at least one output current responsive to the first contributing ionizable species with the concentration of the at least one analyte in the sample.
21. The method of claim 14 , wherein the input signal further includes a third duty cycle having an acyclic scan and a third relaxation, and the method further comprises:
adjusting at least one of a potential of the amperometric excitation in response to the voltammetric output currents and a potential of the acyclic scan in response to the voltammetric output currents,
wherein the adjusting reduces output currents responsive to a second contributing ionizable species in relation to output currents responsive to a first contributing ionizable species in the output signal.
22. The method of claim 21 , further comprising comparing a portion of the output signal including at least one output current responsive to the first contributing ionizable species with a portion of the output signal including at least one output current responsive to the second contributing ionizable species to provide a concentration of the second contributing ionizable species.
23. The method of claim 14 , further comprising comparing a portion of the output signal including at least one output current responsive to a first contributing ionizable species with a portion of the output signal including at least one output current responsive to a second contributing ionizable species to provide a concentration of the second contributing ionizable species.
24. The method of claim 23 , wherein the second contributing ionizable species is an interferent.
25. The method of claim 14 , further comprising adjusting a voltammetric scan rate of the voltammetric excitation in response to the voltammetric output currents.