Electrochemical sensors for analyte detection in water and reference correction method
A sensing platform for continuous water resource monitoring by electrochemical detection and solution parameter correction is provided. The sensing platform employs a solid-state electrolyte three-electrode cell, creating a high ionic strength environment within the solid-state electrolyte membrane, which is in ion exchange equilibria with the sampled solution. This device may be used as a standalone sensor in environments where the water parameters (pH temperature, and ionic strength) are controlled, or in concert with compensation sensors where water parameters are not controlled.
1 . A voltammetric sensor system comprising:
a sensor comprising a working electrode, a counter electrode, and a reference electrode; and
an electronic system connected to the working electrode, the counter electrode, and the reference electrode and being configured to:
apply a voltage difference between the working electrode and the reference electrode; and
conduct a square wave voltammetric scan over at least a portion of an electrochemical window extending from a start scan value to an end scan value using the working electrode, the counter electrode, and the reference electrode,
wherein the electronic system further comprises a dynamic electrochemical window calculator configured to change the end scan value of the electrochemical window to account for drift in the reference electrode,
wherein:
the dynamic electrochemical window calculator is configured to store the start scan value, the end scan value, a baseline current value for current between the working electrode and the counter electrode, a threshold current value for current between the working electrode and the counter electrode that is offset above the baseline current value, and a voltage of significance value that is between the start scan value and the end scan value;
the electronic system is configured to conduct the square wave voltammetric scan starting at the start scan value and progressing in square wave steps to the voltage of significance value and then from the voltage of significance value toward the end scan value; and
the dynamic electrochemical window calculator:
is configured to monitor current between the working electrode and the counter electrode as the square wave voltammetric scan progresses from the voltage of significance value toward the end scan value to determine if said current between the working electrode and the counter electrode exceeds the threshold current value; and
comprises a current limiter that interrupts the square wave voltammetric scan before the square wave voltammetric scan reaches the end scan value to limit oxidation of the working electrode if said current between the working electrode and the counter electrode exceeds the threshold current value after the square wave voltammetric scan has progressed to the voltage of significance value.
2 . The voltammetric sensor system as set forth in claim 1 , wherein the sensor is configured to conduct the square wave voltammetric scan.
3 . The voltammetric sensor system as set forth in claim 1 , wherein the reference electrode comprises a pseudo-reference electrode.
4 . The voltammetric sensor system as set forth in claim 1 , wherein the electronic system is configured to allow the current between the working electrode and the counter electrode to exceed the threshold current value without interrupting the square wave voltammetric scan as the square wave voltammetric scan is progressing from the start scan value to the voltage of significance value.
5 . The voltammetric sensor system as set forth in claim 1 , wherein the dynamic electrochemical window calculator is configured so that, in an event the square wave voltammetric scan is interrupted because the current between the working electrode and the counter electrode exceeds the threshold current value, the end scan value is changed to coincide with a point at which the current between the working electrode and the counter electrode exceeded the threshold current value and caused an interruption.
6 . The voltammetric sensor system as set forth in claim 1 , wherein the dynamic electrochemical window calculator is configured to change the end scan value by moving the end scan value closer to a peak in the current between the counter electrode and the working electrode associated with oxidation of the working electrode in an event the square wave voltammetric scan progresses to the end scan value without causing the current between the working electrode and the counter electrode to exceed the threshold current value.
7 . The voltammetric sensor system as set forth in claim 5 , wherein the dynamic electrochemical window calculator is configured to change the start scan value whenever the dynamic electrochemical window calculator changes the end scan value to shift the electrochemical window without changing a range of the electrochemical window.
8 . The voltammetric sensor system as set forth in claim 1 , wherein the electronic system is configured to conduct a reference scan to determine initial values for at least the baseline current value, the voltage of significance value, and the end scan value.
9 . The voltammetric sensor system as set forth in claim 8 , wherein the reference scan results in a peak in the current between the working electrode and the counter electrode caused by oxidation of the working electrode, and wherein the electronic system is configured to set the initial value of the voltage of significance value to a value that is before the peak caused by oxidation of the working electrode.
10 . The voltammetric sensor system as set forth in claim 1 , wherein initial values for the baseline current value, the voltage of significance value, and the end scan value are stored in the electronic system and based on empirical knowledge of the sensor.
11 . The voltammetric sensor system as set forth in claim 1 , wherein the electronic system is configured to allow a user to input a user-defined offset, the threshold current value being offset above the baseline current value by the user-defined offset.
12 . A method of using the voltammetric sensor system of claim 1 , the method comprising:
applying, via the electronic system, the square wave voltammetric scan over at least a portion of the electrochemical window extending from the start scan value to the end scan value using the working electrode, the counter electrode, and the reference electrode;
determining, via the electronic system, the drift in the reference electrode; and
changing, via the electronic system, the end scan value to account for the drift in the reference electrode.
13 . The method as set forth in claim 12 , wherein changing the end scan value comprises moving the end scan value away from a peak associated with oxidation of the working electrode.
14 . The method as set forth in claim 12 , further comprising changing the start scan value whenever the end scan value is changed to shift an entirety of the electrochemical window.