THIN-LAYER CHRONOAMPEROMETRY AND ITS APPLICATIONS

THIN-LAYER CHRONOAMPEROMETRY AND ITS APPLICATIONPresented by:Parnil Singh (2011CH70172)Shivangi (2011CH70181)CHL 740Chronoamperometry: finite linear diffusionfor complete interfacial oxidation

Chronoamperometry is a technique in electroanalysis in which current drawn at an electrode is measured after a rapid step in the applied voltage.In a thin-layer cell, the anode and cathode are separated by a microscale distance. This means that chemical species transport across the cell is fast, so an analyte in the cell can be consumed exhaustively after only a few seconds. By integrating the current transient (chronoamperogram), the initial concentration of analyte can be determined.

2Parameters L=60um Thin layer cell thickness c_bulk = 1 mol/m^3 Bulk concentration of reactant A_el = 1 mm^2 Electrode area D = 1e-9 m^2/s Diffusion coefficient t_rise = 1us Potentiostatic rise time x_step =sqrt(2*t_rise*D) Resolved diffusion layer thicknessThin Layer Chronoamperometry

Total Current

Comparison of Total current and Cottrell current

6Extent of Reaction

Glucose Biosensor Major reactions occurring:C6H12O6 + FAD C6H10O6 + FADH2FADH2 + 2[Fe(CN)6]-3 FAD + 2[Fe(CN)6]-4 + 2H+C6H10O6 + H2O C6H11O7 + H+

Parameters

c_glucose_ext =5 umol/L External glucose concentration

c_ferro_ext =1 umol/L Ferrocyanide concentration

c_ferri_ext 50[mmol/L] Ferricyanide concentration

V_max= 1.5e-5 mol/L/s Maximum rate of reaction

Km = 0.5 mmol/L Michaelis-Menten constant

Result

ReferencesAnalytical and Physical Electrochemistry, Hubert H. GilbertElectrochemical Glucose Biosensors, Joseph Wang, Chem. Rev. 2008, 108, 814-825