Determination of cardiac glycosides by adsorptive stripping voltammetry

Abstract

Several cardiac glycosides are shown to adsorb strongly on to mercury electrodes. Using this phenomenon to accumulate these compounds at the static mercury-drop electrode prior to differential-pulse voltammetric measurements, nanomole sensitivities are readily achieved. The adsorptive stripping response was evaluated with respect to accumulation time and potential, concentration dependence, electrolyte, the presence of surfactants and other variables. With 5-min accumulation, peak current enhancements of 32, 31 and 11 are observed for 3 × 10^–8M digoxin, digitoxigenin and digitoxin, respectively, compared with solution-phase pulse voltammetry. The relative standard deviation at the 5 × 10^–8M level ranges from 3 to 6%. Detection limits are 2.3 × 10^–10M for digoxin, 7.5 × 10^–10M for digitoxigenin and 8 × 10^–10M for digitoxin (15-min accumulation).