Method and apparatus for processing electrochemical signals

Abstract

Systems and methods are provided herein for improving the selectivity and productivity of sensors via digital signal processing techniques. According to one illustrative embodiment, in an electrochemical method for monitoring of a select analyte in a mixed sample with an interfering analyte, an improvement is provided that includes applying a large amplitude potential stimulus waveform to the sample to generate a nonlinear current signal; and resolving a signal contribution from the select analyte in the generated signal by a vector projection method with an analyte vector comprising a plurality of real and imaginary parts of one or more Fourier coefficients at one or more frequencies of a reference current signal for the select analyte.

1 - 19 . (canceled) 
   
   
       20 . A method of constructing an estimation equation for monitoring a select analyte in a mixed sample with an interfering analyte wherein said select analyte and said interfering analyte both generate a current in response to application of a common potential, the method comprising: selecting a large amplitude potential stimulus waveform to generate a nonlinear current signal when applied to the sample said waveform comprising a plurality of portions in which change in potential over time is positive in alternating arrangement with a plurality of portions in which change in potential over time is negative; selecting signal features of the current signal to use as parameters; applying the waveform to samples containing different concentrations of both the select and interfering analytes, and measuring the resulting reference current signals; computing values of each parameter for each reference signal; constructing the estimation equation as a linear estimator, having a select number of the parameters, from the computed values and with sufficient accuracy to estimate a concentration of the select analyte in the samples. 
   
   
       21 . The method of  claim 20 , wherein the parameters include one or more of: one or more real or imaginary parts of a Fourier coefficient at one or more frequencies, for all or one or more portions of the current signal; a slope of the current signal; a rate of rise or decay of some portion of the current signal; a potential at which a peak occurs in the current signal; and a value of a peak in the current signal. 
   
   
       22 . The method of  claim 20 , wherein constructing a linear estimator includes determining the select number of the parameters and then selecting the linear estimator with the select number of parameters which exhibits a specified level of performance. 
   
   
       23 . The method of  claim 20 , wherein constructing the linear estimator includes use of a randomized cross validation process. 
   
   
       24 . The method of  claim 20 , wherein constructing the linear estimator includes determining the sufficient accuracy with a root mean squared process. 
   
   
       25 . The method of  claim 20 , wherein constructing the linear estimator includes selecting the estimator which exhibits a desired performance. 
   
   
       26 . The method of  claim 20 , wherein constructing the linear estimator includes Jul. 12, 2006 selecting the optimal number of the parameters based on a lowest estimation error. 
   
   
       27 - 44 . (canceled) 
   
   
       45 . The method of  claim 20 , wherein the waveform comprises a plurality of portion in which change in potential over time is positive in alternating arrangement with a plurality of portions in which change in potential over time is negative. 
   
   
       46 . The method of  claim 45 , wherein the absolute value of the positive change in potential over time is equal to the absolute value of the negative change in potential over time. 
   
   
       47 . The method of  claim 45 , wherein the parameters include one or more of: one or more real or imaginary parts of a Fourier coefficient at one or more frequencies, for all or one or more portions of the current signal; a slope of the current signal; a rate of rise or decay of some portion of the current signal; a potential at which a peak occurs in the current signal; and a value of a peak in the current signal. 
   
   
       48 . The method of  claim 45 , wherein constructing a linear estimator includes determining the select number of the parameters and then selecting the linear estimator with the select number of parameters which exhibits a specified level of performance. 
   
   
       49 . The method of  claim 45 , wherein constructing the linear estimator includes use of a randomized cross validation process. 
   
   
       50 . The method of  claim 45 , wherein constructing the linear estimator includes determining the sufficient accuracy with a root mean squared process. 
   
   
       51 . The method of  claim 45 , wherein constructing the linear estimator includes selecting the estimator which exhibits a desired performance. 
   
   
       52 . The method of  claim 45 , wherein constructing the linear estimator includes selecting the optimal number of the parameters based on a lowest estimation error. 
   
   
       53 . The method of  claim 45 , wherein the waveform is a triangular wave. 
   
   
       54 . The method of  claim 53 , wherein the parameters include one or more of: one or more real or imaginary parts of a Fourier coefficient at one or more frequencies, for all or one or more portions of the current signal; a slope of the current signal; a rate of rise or decay of some portion of the current signal; a potential at which a peak occurs in the current signal; and a value of a peak in the current signal. 
   
   
       55 . The method of  claim 53 , wherein constructing a linear estimator includes determining the select number of the parameters and then selecting the linear estimator with the select number of parameters which exhibits a specified level of performance. 
   
   
       56 . The method of  claim 53 , wherein constructing the linear estimator includes use of a randomized cross validation process. 
   
   
       57 . The method of  claim 53 , wherein constructing the linear estimator includes determining the sufficient accuracy with a root mean squared process. 
   
   
       58 . The method of  claim 53 , wherein constructing the linear estimator includes selecting the estimator which exhibits a desired performance. 
   
   
       59 . The method of  claim 53 , wherein constructing the linear estimator includes selecting the optimal number of the parameters based on a lowest estimation error. 
   
   
       60 . The method of  claim 20 , wherein the absolute value of the positive change in potential over time is equal to the absolute value of the negative change in potential over time. 
   
   
       61 . The method of  claim 20 , wherein the parameters comprise one or more real or imaginary parts of a Fourier coefficient at one or more frequencies, for all or one or more portions of the current signal. 
   
   
       62 . The method of  claim 20 , wherein the parameters comprise a slope of the current signal. 
   
   
       63 . The method of  claim 20 , wherein the parameters comprise a rate of rise or decay of some portion of the current signal. 
   
   
       64 . The method of  claim 20 , wherein the parameters comprise a potential at which a peak occurs in the current signal. 
   
   
       65 . In an apparatus for monitoring a select analyte in a mixed sample with an interfering analyte, the improvement wherein the apparatus comprises means for applying a large amplitude potential stimulus waveform to the sample to generate a nonlinear current signal; and for resolving a signal contribution from the select analyte in the generated signal by a vector projection method with an analyte vector comprising a plurality of real and imaginary parts of one or more Fourier coefficients at one or more frequencies of a reference current signal for the select analyte. 
   
   
       66 . An apparatus comprising: a potentiostat circuit for applying a voltage waveform to and detecting a resulting current from an electrode system; at least one memory having program instructions and a processor configured to execute the program instructions to perform the operations of: applying a large amplitude potential stimulus waveform to the sample to generate a nonlinear current signal; measuring the generated signal; computing at least one Fourier coefficient of a desired frequency component of all or some portion of the generated signal; and determining a concentration of the select analyte in the mixed sample by use of the at least one Fourier coefficient to resolve an estimation equation based on analyte vectors for each of the select and interfering analytes, wherein the electrode system comprises a biological recognition element. 
   
   
       67 . The apparatus of  claim 66 , wherein the biological recognition element is an enzyme.