Determination of the real electrochemical surface areas of screen printed electrodes

• US 20100187132A1
• Filed: 12/17/2009
• Published: 07/29/2010
• Est. Priority Date: 12/29/2008
• Status: Abandoned Application

• Current Assignee: Sanofi-Aventis Deutschland GmbH (Sanofi )
• Original Assignee: Sanofi-Aventis Deutschland GmbH (Sanofi )
• Inventors: Alden, Don
• Application Number:
  US12/640,446
• Publication Number:
  US 20100187132A1
• Time in Patent Office: Days
• US Class Current: 205/790.500
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771
• CPC Class Codes: G01N 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence

Abstract

A method is provided for determining a real electrochemical surface area of a working electrode (WE) of a screen printed sensor. A concentration of a mediator incorporated in a WE paste is determined. The diffusion coefficient of the mediator is then ascertained. A final real electrochemical surface area of the WE is then made.

Claims

1. A method for determining a real electrochemical surface area of a working electrode (WE) of a screen printed sensor, comprising:

determining a concentration of a mediator incorporated in a WE paste;

determining a diffusion coefficient of the mediator; and

determining a final real electrochemical surface area of the WE.

2. The method of claim 1, wherein the screen printed sensor is a three electrode system that includes, two printed carbon electrodes acting as a WE and counter electrode, and a printed Ag/AgCl reference electrode.

3. The method of claim 1, wherein the WE paste is a complex matrix structure containing both conducting elements and assay reagents, and wherein a concentration of the mediator incorporated in the WE paste is unknown.

4. The method of claim 1 wherein step (a) includes:

(a) running cyclic voltammetry; and

(b) applying a standard addition method.

5. The method of claim 4, wherein in step 4(a), different solutions of mediator with different concentrations in PBS are prepared, cyclic voltammograms are run to observe a (Eox)of the WE after applying increased concentrations of mediator on the WE, and wherein a specific electrochemical response corresponds to an added concentration of the mediator as well as of an unknown concentration of the mediator present in the WE paste.

6. The method of claim 4 wherein, step 4(b) includes, plotting oxidation peak currents observed in the CVs against a concentration of the added mediator, wherein after calculating a slope and an intercept of the oxidation peak currents the unknown concentration of the mediator is calculated by dividing the intercept with the slope.

7. The method of claim 1, wherein calculation of the diffusion coefficient of the mediator includes:

running cyclic voltammetry under three different scan rates to create electrode cyclic voltammograms; and

plotting oxidation peak currents against a square root of scan rates.

8. The method of claim 7, wherein in step 7(a) PBS is run on the electrode cyclic voltammograms under three different scan rates to obtain three different oxidation peak currents that correspond to the different scan rates.

9. The method of claim 7, wherein in step (7b), the slope of the plot of the three oxidation peak currents (Eox) against the square root of the scan rates is equal to a diffusion coefficient of the mediator.

10. The method of claim 1 wherein, said step (1c) Chronocoulometry is used to determine the real electrochemical surface area of the WE.

11. The method of claim 10, wherein Chronocoulometry is a measurement of charge as a function of time, wherein an analysis of chronocoulometric data is based on an Anson equation that defines a charge-time dependence for linear diffusion control:

Q=2nFACD^1/2π

<sup>−

1/2</sup>t<sup>−

1/2</sup>

where;

Q is the charge (coulombs);

n is the number of electrons transferred;

A is the real electrochemical surface area of the WE (cm²);

F is Faraday'"'"'s constant (96,485 coulombs/mole);

C is the concentration of the mediator;

D is a diffusion coefficient of the mediator (cm²/sec); and

t is time (sec).

12. The method of claim 11, wherein the Anson plot is a plot of Q vs. t^1/2 and transforms data into a linear relationship whose slope (a) is equal to:

2nAFCD^1/2/π

^1/2

where;

n is the number of electrons transferred;

A is the real electrochemical surface area of the WE (cm²);

F is Faraday'"'"'s constant (96,485 coulombs/mole);

C is the concentration of the mediator (moll/cm³); and

D is a diffusion coefficient of the mediator (cm²/sec).