Determination of thiopentone sodium in aqueous and biological media by cathodic stripping voltammetry

A simple and more sensitive cathodic stripping voltammetric method is described for the determination of short-anaesthetic drug thiopentone-sodium (TPS). The method is based generally on the formation of a slightly soluble mercury salt of TPS with Hg onto HMDE surface. The reduction current of the formed salt was measured by both linear sweep (LSCSV) and differential purse cathodic stripping voltammetry (DPCSV). Different variables were studied and optimized. Four-fold enhancement in the current is observed in the presence of trace Mg ion. The role of Mg ion is discussed in a manner that hydroxide species are formed and accelerate the adsorption of the drug. As low as 1 x 10(-8) mol l(-1) (2.60 ppb) and 2 x 10(-9) mol l(-1) (0.53 ppb) with accumulation time 240 and 300 s, in the absence and in the presence of Mg(II), respectively, have been determined using both techniques, with the relative standard deviation up to 3.5% (n=4). The interferences of some metal ions, ascorbic acid and amino acids were studied. The determination of the drug in pure pharmaceutical dosage form, urine, and human serum samples have been successfully carried out. The results were compared favorably with the official methods. (C) 2000 Elsevier Science B.V. All rights reserved.