Fullerene-C60-modified Edge Plane Pyrolytic Graphite Electrode for the Determination of Dexamethasone in Pharmaceutical Formulations and Human Biological Fluids

Electrochemical behaviour of dexamethasone at the fullerene-C(60)-modified pyrolytic graphite electrode (PGE) has been investigated using Osteryoung square wave voltammetry (SWV). Compared to a bare PGE and fullerene-C(60)-modified glassy carbon electrode (GCE), the fullerene-C(60)-modified edge plane PGE exhibited an apparent shift of the peak potential to less negative potentials with a marked enhancement in the current response of dexamethasone. The peak potential was linearly dependent on pH with dE(p)/dpH as 59 mV/pH. Calibration plot having good linearity with a correlation coefficient 0.9983 is obtained in the concentration range of 0.05-100 microM and the sensitivity of the method has been found to be 0.685 microA microM(-1). The detection limit is estimated to be 5.5 x 10(-8)M. The electrode showed good sensitivity, stability and reproducibility. The practical analytical utility of the method is illustrated by quantitative determination of dexamethasone in several commercially available pharmaceutical formulations and human blood plasma of patients being treated with dexamethasone. HPLC method was used to compare the results obtained for the quantitative estimation of dexamethasone in biological fluids.