Thiourea (TU) has various industrial, agricultural and analytical applications. The material is widely used in photography as a fixing agent and to remove stains from negatives, and in agriculture as fungicide, herbicide and rodenticide. TU is also used as a spectrophotometric reagent for the determination of several metals.Various methods have been proposed for the determination of TU, such as Raman spectrometry 1 , polarography 2 , stripping voltammetry 3 , high-performance liquid chromatography 4 , kinetic methods 5,6 , piezoelectric detection 7 , potentiometric method 8 , pulsed amperometry 9 , oxalate-catalyzed oxidimetric method with KMnO 4 10 , electrokinetic reversed-phase chromatography 11 and FIA fluorometry. 12 Despite the large number of methods, most of them lack either sensitivity or simplicity. The CL method has been widely used because of its high sensitivity and simplicity. Ru(bipy) 3 2+ is a widely used electrogenerated CL reagent 13 and has become a useful CL reagent. It has been used for the determination of some organic acids in the Ru(bipy) 3 2+ -Ce(IV) chemiluminescence system. 14,15 We used it in TU-KMnO 4 system to determine TU.In this paper the development of the TU-KMnO 4 CL method for the determination of thiourea and its application to the sample analysis is presented. The emission intensity of the system is greatly enhanced by the presence of Ru(bipy) 3 2+ and surfactant sodium dodecylbenzene sulfonate (SDBS). It was used for the determination of thiourea in grape wine.
Experimental
ApparatusAn LKB 1251 luminometer with a Dispenser SVD and a Dispenser controller DC (Pharmacia LKB Biotechnology AB, Sweden) and an Epson LX-800 printer were used.
ReagentsAll solutions were prepared from analytical-reagent grade materials in doubly distilled water.A 0.1 mol/l stock solution of thiourea was prepared daily by dissolving 0.741 g of thiourea in water and diluting with water to 100 ml. Ru(bipy) 3 2+ (prepared in our laboratory 15 ) solutions were prepared by dissolving a weighed amount of Ru(bipy) 3 Br 2 in water and diluting to volume. The concentration of the stock solution is 4.48×10 -3 g/ml. Potassium permanganate stock solutions were prepared by dissolving a weighed amount of KMnO 4 in water and adding a pre-determined volume of 1.0 mol/l H 2 SO 4 and diluting to volume. Working solution were prepared by dilution of the stock solution with 1.0 mol/l H 2 SO 4 and water.The 2.0 % solutions of Tween-20, Tween-40, Tween-80 and Triton X-100 were prepared by dissolving 2.0 g in water and diluting with water to 100 ml. The 1.0×10 -2 mol/l solutions of sodium dodecyl benzene sulfonate (SDBS), tetradecyl pyridine bromide (TPB), cetyl pyridine bromide (CPB), cetyl trimethyl ammonium bromide (CTAB) were prepared by dissolving 0.348, 0.356, 0.384, or 0.364 g of them in water and diluting with water to 100 ml.
ProcedureA 0.2 ml amount of thiourea and 0.2 ml of 2×10 The emission produced by thiourea in oxidation by permanganate in acidic solution in the presence of Ru(bipy)3 2+ is used to deter...
