Determination of methylprednisolone acetate in biological fluids at gold nanoparticles modified ITO electrode

The electrochemical behavior of a corticosteroid methylprednisolone (NIP), used for doping, has been studied at gold nanoparticles modified indium tin oxide (nanoAu/ITO) electrode. The nanoAu/ITO electrode exhibited an effective catalytic response towards its oxidation and lowered its oxidation potential by similar to 127 mV when compared with bare ITO electrode. Oxidation of NIP has been carried out in phosphate containing electrolyte in the pH range 2.13-10.00 and a well-defined oxidation peak was noticed. Linear concentration curves are obtained over the concentration range 0.01 - 1.0 mu M with a detection limit of 2.68 x 10(-7) M at nanoAu/ITO electrode. A diffusion coefficient of 2.36 x 10(-6) cm(2)/s is calculated for MP using chronoamperometry. The proposed method is effectively applied to detect the concentration of MP in pharmaceutical formulations and human blood plasma and urine samples. A comparison of NIP concentration determined in blood plasma and urine by the proposed method and GC/MS indicated that the results are essentially similar. It is believed that the method will be useful in determining this drug in case of doping. (c) 2007 Elsevier B.V. All rights reserved.