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...
A new chemiluminescence method is described for the determination of 6-mercaptopurine.In the presence of tris(2,2'-bipyridine)ruthenium(II), 6-mercaptopurine (6MP) and hydrogen peroxide, upon the addition of hydroxide ion, resulted in intense light emission. The emission intensity is greatly enhanced by the presence of Tween-20. The linear range and detection limit of 6MP are 1.4X10-5 -1.4X10.8 g/ml and 3X10-10 g/ml, respectively. The method was evaluated by carrying out an interference study with common excipients and other coexisting compounds, by a recovery study and by the analysis of commercial formulation. A satisfactory result was obtained. KeywordsChemiluminescence, 6-mercaptopurine, tris(2,2'-bipyridine)ruthenium (II) 6-Mercaptopurine (6MP) is a well-known clinical agent for therapy of human leukemias and an immunosuppressive drug.' Most of the methods described for the determination of 6MP are based on the electrochemical characteristics. But these methods have poor sensitivity and selectivity. Many metal ions and anion radicals interfere with the determination of 6MP.Tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) is an extremely versatile base reactant for a variety of chemiluminescent processes.2-4 The most elegant ways to obtain chemiluminescence (CL) from Ru(bpy)32+ solution is to produce the oxidized and/or reduced form of the complex "in situ" by electrochemical methods. However, no analytical application that uses Ru(bpy)32+ as CL reagent in solution directly has yet been presented.We report here a solution CL system involving Ru(bpy)32+, 6MP, H2O2 and OH-. In the presence of Tween-20, the linear range and detection limit of 6MP are 1.4X108 -1.4X 10-5 g/ ml and 3.0X10'° g/ ml, respectively.hydroxide and diluting to 100.0 ml with water. This was kept at 4° C in a refregerator.All other reagents were of analytical grade or better and all water used was doubly distilled in a fused-silica apparatus.Procedures A 0.2 ml portion of 0.5 mmol/l Ru(bpy)32+, 0.2 ml of 4.0% Tween-20, 0.2 ml of 5.0 tg 6MP and 0.2 ml of 0.45% hydrogen peroxide were mixed in reaction cuvettes. Then the mixture was moved into a measuring chamber with a constant temperature of 25° C. After the start button was pushed, a 0.2 ml of 0.4 mol/l sodium hydroxide was injected into the reaction cuvettes automatically and the CL produced was measured immediately (see Fig. 1). The calibration graph of emission intensity vs. concentration of 6MP was constructed and the 6MP contents of the samples were determined. Each standard or sample solution was measured five times. Results and Discussion ExperimentalApparatus and reagents LKB 1251 luminometer, dispenser SVD and dispenser controller DC (Pharmacia LKB Biotechnology AB, Sweden), with a Epson LX-800 printer (Seiko Epson Corp. Japan) were used. A 1.0 mmol/ 1 stock solution of [Ru(bpy)3]Br2 (prepared in our laboratory) was prepared by dissolving 745.7 mg [Ru(bpy)3]Br2 in water and diluting with water to 11.A 0.5 mg/ml stock solution of 6MP was preapred by dissolving 50.0 mg of it in 5.0...
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