Adsorptive stripping voltammetric determination of zopiclone in tablet dosage forms and human urine

Adsorptive stripping voltammetric (AdSV) techniques were proposed for the direct quantitative determination of zopiclone (ZP) in spiked human urine and tablet dosage forms for first time. The electrochemical oxidation and determination of ZP were easily carried out on glassy carbon electrode (CGE) using a variety of voltammetric techniques. Different conditions were investigated to optimize the analytical determination of ZP. The dependence of the intensities of currents and potentials on pH, concentration, scan rate, deposition time, deposition potential, and nature of the buffer were investigated. Oxidation of ZP was found to be adsorptive-controlled and irreversible. The best results for the determination of ZP were obtained by using differential pulse adsorptive stripping (DPAdSV) and osteryoung square wave voltammetric (OSWAdSV) techniques in Britton-Robinson buffer at pH 7.08 after a pre-concentration period of 120 s at 0.60 V. The peak current showed a linear dependence on the ZP concentration in the range of 6 x 10(-7) to 2 x 10(-5) mol L(-1) for both techniques. The achieved limits of detection and quantitation were 2.78 x 10(-7) and 5.28 x 10(-7) mol L(-1) for DPAdSV; 1.70 x 10(-7) and 5.78 x10(-7) mol L(-1) for OSWAdSV, respectively. The proposed techniques were successfully applied to direct determination of ZP in tablet dosage form and spiked human urine samples. Excipients did not interfere with the determination. Precision and accuracy of the developed method were checked by recovery studies in tablet dosage forms and spiked urine samples.