FAST SQUARE WAVE VOLTAMMETRIC DETERMINATION OF CORTISOL IN PHARMACEUTICAL FORMULATION AND HUMAN URINE USING THE BARE GLASSY CARBON ELECTRODE

A simple, fast and sensitive electrochemical method for the direct determination of cortisol in commercial pharmaceutical product and human urine was developed. The electrochemical reduction and quantitative analysis of cortisol were performed in Britton Robinson Buffer Solution (BRBS, pH 2.0) with a bare glassy carbon electrode (GCE) using cyclic voltammetry (CV) and square wave voltammetry (SWV). The compound showed one irreversible and adsorption-controlled reduction peak in CV. When SWSV mode is used, the compound yielded a well-defined voltammetric response at about -1.14 V (vs. Ag/AgCl) in BRBS at pH 2.0. Experimental results revealed an excellent linear correlation between the peak current and the concentration in the range of 1-50 μg mL-1 (2.8×10-6-1.4×10-4 mol L-1). Detection and quantification limits were found to be 0.069 μg mL-1 (1.9×10-7 mol L-1) and 0.229 μg mL-1 (6.32×10-7 mol L-1), respectively. Precision and accuracy of the developed method were checked by recovery studies in spiked tablets and urine