Robert Eliason

The measurement of precise linear sweep voltammetry slopes and the effect of IR compensation on the measurement precision

Abstract The level of measurement precision attainable during the acquisition of linear sweep voltammetry (LSV) electrode peak potentials ( E p ) and half-peak potentials ( E p/2 ) was examined for a well-defined electrode process: the reduction of 1,1-diphenylethylene in DMF containing methanol. The standard deviations in replicate measurements of either E p or E p/2 were of the order of +0.05 mV. Changing only one variable, the voltage sweep rate ( v ), for measurements over a period of ca. 30 min on the same electrolyte solution resulted in standard deviations of ca. ±0.1 mV/decade in the LSV slope, Δ E p /Δ log v . The standard deviations in Δ E p /Δ log v obtained from the same process where measurements were made on different solutions with the cell and electrodes being cleaned between measurements was observed to be of the order of ±0.3 mV/decade. Using mercury electrodes with a surface area of the order of a few mm 2 . E p values were observed to be independent of the degree of IR compensation as long as the substrate concentration was 0.5 m M or less. At higher substrate concentrations, the degree of IR compensation becomes increasingly important. A procedure for the measurement of Δ E p /Δ log v and the adjustment of the IR compensation feedback circuit is recommended. It is concluded that measurement precision of ±0.3 mV/decade can be readily accomplished as long as the electrode process is free of complications such as product adsorption.