Analysis of spironolactone residues in industrial wastewater and in drug formulations by cathodic stripping voltammetry

The redox behavior of spironolactone (SP) drug in Britton-Robinson (BR) buffer of pH 2-11 was investigated by differential pulse cathodic stripping voltammetry (DPCSV) and cyclic voltammetry (CV) at hanging mercury dropping electrode (HMDE). At pH 9-10.5, the DPCSV of SP drug showed two cathodic peaks at -1.15 and -1.38 V at the HMDE vs. Ag/AgCl reference electrode. In the CV, at pH 9-10, the dependence of the cathodic peak current, Ip , c and peak potential, Ep,c of the second peak (Ep,c2) on the scan rate (ν) and on the depolizer (SP) concentrations was typical of an electrode coupled (EC) chemical reaction type mechanism. The plot of Ip , c at -1.380 V of the DPCSV vs. SP concentration at pH 9 was linear over the concentration range of 1.2×10-10-9.6×10-7 M. The lower limit of detection (LLOD) and limit of quantification (LOQ) of the drug were 1.1×10-11 and 4.14×10-11 M, respectively. The method was successfully applied for the analysis of SP residues in industrial wastewater, in pure form (98.2±3.1%) and in drug formulations e.g. Aldactone® tablet (98.35±2.9%).The method was validated by comparison with HPLC and the official data methods.