Polymer-modified glassy carbon electrode for the electrochemical detection of quinine in human urine and pharmaceutical formulations

Glassy carbon electrode was modified by electropolymerization of 4-amino-3-hydroxynaphthalene sulfonic acid. Cyclic voltammetric study of quinine showed higher current response at the modified electrode compared to the bare and activated glassy carbon electrodes in pH 7.0 phosphate buffer solution. Under optimized conditions, a calibration curve was obtained by square wave voltammetry at the modified electrode. The linear relationship between the peak current and the concentration of quinine in the range of 1.0 × 10−7 to 1.0 × 10−5 M was Ipa (in microamperes) = 6.26C (in micromolars) + 0.2997 (R2 = 0.999). The detection limit calculated (S/N = 3) was 1.42 × 10−8 M, which is much lower than similar reports. The method was successfully applied for the determination of quinine in spiked human urine, and pharmaceutical formulations and recovery values >90 % were obtained.