Kinetic spectrophotometric determination of thiobenzamides and their partition coefficients in water/1-octanol by using an iodine/azide indicator reaction

The kinetic method is based on catalysis, by thiobenzamide and/or its derivatives, of the oxidation of azide by iodine at 25°C in 0.1 M acetate buffer (pH 4.7) containing iodate, iodide and azide. Thiobenzamide and its 4-methoxy-, 4-methyl-, 4-chloro- and 4-nitro derivatives (0.5–3 μM) are determined by measuring the decrease in the absorbance of iodine at 350 nm at a fixed time (2 min). The detection limits are 0.05–0.1 μM and the relative standard deviations are <2%. The proposed method is used to determine the partition coefficients of thiobenzamide and its derivatives in water/1-octanol; the equilibrated aqueous phase was analysed.