Validation and application of the square wave voltammetry method for the electrochemical determination of eszopiclone in pharmaceutical formulations and human biological fluids using glassy carbon electrode

A buffer solution of Britton-Robinson (B-R) pH 6.5 was utilized to validate and apply a square wave voltammetry (SWV) method for the electrochemical determination of Eszopiclone (ESP) in pharmaceuticals and biological samples. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods were employed in the initial study of the voltammetric behavior of the ESP compound. The rotating glassy carbon (GC) indicator electrode (2.0 mm2), Pt auxiliary electrode, and Ag/AgCl reference electrode were used for ESP determination. ESP was analyzed to produce a sharp reduction peak at a potential of -750 mV. The best shape and high sensitivity of SWV cathodic current for ESP, were observed using GC electrode, B-R, pH 6.5, accumulation time (tacc) of 60-second, accumulation potential (Eacc) of - 0.1 V, amplitude voltage of 150 mV, frequency of 15 Hz, scan rate of 150 mV s-1, and stirrer rate of 1000 round per minute (rpm). The electroanalytical performance of the SWV method was evaluated through study of repeatability, stability, calibration curve, recovery, and limits of detection and quantification (LOD,LOQ). Under the optimal conditions, the SWV response was linear in the range from 3 x 10-6 to 5 x 10-5 mol/L (n = 10). The SWV method achieved a LOD of 1.9 x 10-8 mol/L (7.5 ppb), and a LOQ of 6.41 x 10- 8 mol L-1 (24.93 ppb). The validated SWV method was appeared the good repeatability, sensitivity and stability for the determination of ESP. It was given a very stable SWV current for 90 min, with a 0.141 % relative standard deviation (RSD%). The SWV method was applied to the determination of ESP in pharmaceutical tablets and biological samples.