Electrochemical studies of quinine in surfactant media using hanging mercury drop electrode: A cyclic voltammetric study

The electrochemical behavior of quinine was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV) using surfactant. The reduction peak current of quinine increases remarkably in presence of 1% CTAB. Its electrochemical behavior is quasi-reversible in the Britton–Robinson buffers of pH 10.38 by exhibiting the well-defined single cathodic and anodic waves and the ratio of Ipa/Ipc approaching one at the scan rate of 500 mV s−1. On the basis of CV, SWV and Coulometry, electrochemical reduction mechanism of quinine has been proposed which has shown that protonation occurs on the nitrogen of the quinoline moiety. Linearity was obtained when the peak currents (Ip) were plotted against concentrations of quinine in the range of 30.0–230.0 ng mL−1 with a detection limit of 0.132 ng mL−1 in SWV and 90.0–630.0 ng mL−1 with a detection limit of 0.238 ng mL−1 in DPV. Fast and sensitive SWV has been applied for the quantitative analysis of quinine in bark of Cinchona sp. and in soft drinks and a good recovery was obtained. The accuracy and precision of the method are determined and validated statistically. No interferences from other food additives were observed. The relative standard deviation for intraday and interday assay was 0.89 and 0.73% (n = 3) respectively.

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► Quinine yields a well-defined reduction peak at HMDE in presence of 1% CTAB.
► Protonation on the nitrogen of the quinoline moiety and quasi-eversible deduction.
► Detection limit obtained is 0.132 ng mL−1 using square wave voltammetry.
► Determination in Cinchona bark, soft drinks and pharmaceutical formulation.
► Cinchona bark 75.31 ± 0.052 mg/g of its dry weight and soft drinks 81.4 ± 0.08 μg mL−1.