Rapid determination of bisacodyl in flow injection system combination by a novel sensitive adsorptive square-wave voltammetry

A continuous square-wave voltammetric study of bisacodyl at gold microelectrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorpted at −300 mV, giving rise to change in the current of well-defined oxidation peak of gold. Signal-to-noise ratio has significantly increased by application of discrete fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as SW frequency, eluent pH, and accumulation time were optimized.The monitored adsorptive current was directly proportional to the concentration of bisacodyl and it shows a linear response in the range from 0.008 to 14.5 nM (correlation coefficient = 0.9995) and the detection limit (S/N = 3) is 1.0 × 10−12 mol l−1 at an accumulation time of 700 ms. The developed adsorptive stripping voltammetry (AdSV) procedure shows a good reproducibility, the relative standard deviation R.S.D.% (n = 10) at a concentration level of 5.0 × 10−8 mol l−1 was 0.94%. Possible interferences by other pharmaceutical drugs and surfactants have been also evaluated. The applicability of this approach was illustrated by the determination of bisacodyl in pharmaceutical preparation and biological fluids such as serum and urine.