The voltammetric oxidation and determination of chlorpheniramine maleate (CPM) was studied at a carbon paste electrode (CPE) in the presence of sodium-dodecyl sulfate (SDS) by cyclic and differential pulse voltammetry. The results indicated that the voltammetric response of chlorpheniramine maleate was markedly increased in the low concentration of SDS, suggesting that SDS exhibits observable enhancement effect to the determination of chlorpheniramine maleate. Under the optimal conditions the peak current was proportional to chlorpheniramine maleate concentration in the range of 8.0 10 À6 to 1.0 10 À4 M with detection limit of 1.7 10 À6 M by differential pulse voltammetry. The proposed method was successfully applied to the determination of chlorpheniramine in pharmaceutical and urine samples.

Oxidation of thiamine hydrochloride (vitamin B 1 ) by cerium(IV) mediated by micro amounts (10 -6 mol dm -3 ) of ruthenium(III) in aqueous perchloric acid medium has been studied spectrophotometrically at 25°C and I = 1.10 mol dm -3 . The reaction is first order in both cerium(IV) and ruthenium(III) concentrations. The order with respect to vitamin B 1 concentration varies from first order to zero order as the vitamin B 1 concentration increases. An increase in perchloric acid concentratrion decreases the reaction rate. The active species of oxidant and catalyst are [Ce(OH) 3? ] and [Ru(H 2 O) 6 ] 3? . A possible mechanism is proposed and reaction constants involved have been determined. The activation parameters for the slow step of the mechanism are determined.

The manganese(II) catalysed oxidation of glycerol by cerium(IV) in aqueous sulphuric acid has been studied spectrophotometrically at 25°C and I = 1.60 mol dm -3 . Stoichiometry analysis shows that one mole of glycerol reacts with two moles of cerium(IV) to give cerium(III) and glycolic aldehyde. The reaction is first order in both cerium(IV) and manganese(II), and the order with respect to glycerol concentration varies from first to zero order as the glycerol concentration increases. Increase in sulphuric acid concentration, added sulphate and bisulphate all decrease the rate. Added cerium(III) retards the rate of reaction, whereas glycolic aldehyde had no effect. The active species of oxidant and catalyst are Ce(SO 4 ) 2 and [Mn(H 2 O) 4 ] 2? . A mechanism is proposed, and the reaction constants and activation parameters have been determined.

The reaction kinetics for the oxidation of theophylline by permanganate ions have been investigated in perchloric acid medium using spectrophotometric techniques at 25 • C, and at constant ionic strength 1.60 mol·dm −3 , under pseudo first order conditions. An autocatalyzed reaction is observed due to one of the products formed is Mn(II). The orders with respect to theophylline and Mn(VII) were both found to be unity, whereas fractional order is observed with respect to the autocatalyst, Mn(II). The rate of the reaction increases as the concentration of acid increases, but the order with respect to acid concentration is less than unity. The influence of temperature on the rate of reaction was studied. Based on the experimental results a suitable mechanism is proposed. The activation and thermodynamic parameters were determined with respect to slow reaction step.