Abstract
Edge plane pyrolytic graphite electrode (EPPGE) modified with single-wall carbon nanotubes (SWNTs) has been used as a sensor to determine triamcinolone, abused by athletes for doping. A comparison of the voltammetric behavior between SWNTs modified EPPGE and fullerene - C-60-modified EPPGE indicated that SWNTs; modified EPPGE is more sensitive. The electrode exhibited an effective catalytic response with good reproducibility and stability. The effect of several parameters such as pH, square wave frequency and steroid concentration were studied. The square wave voltammetric response of the electrode to triamcinolone is linear in the range 0.1-25 nM with a detection limit and sensitivity of 8.9 x 10(-10) M and 2.06 mu A nM(-1), respectively The method was applied for the determination of triamcinolone in several commercially available pharmaceuticals and real urine samples obtained from patients undergoing pharmacological treatment with triamcinolone. A comparison of the observed results with HPLC analysis indicated a good agreement. The product obtained after reduction of triamcinolone was also characterized using H-1 NMR and GC-MS and the site of reduction is found to be carbonyl group at position 20. The method described is rapid. simple and accurate and can be easily applied for detecting cases of doping. (C) 2009 Elsevier B.V. All rights reserved.