Estudo da formação do 4,5-benzopiazoselenol nas misturas homogêneas dos solventes água-etanol-clorofórmio(ou tolueno)

Abstract

In this work the formation of the 4,5-benzopiazoselenol in the homogeneous system of the solvents water-ethanol-chloroform(or toluene) mixture it is presented evaluating the behavior of the analytical response, measured the λmax = 380 nm. Using classic and chemometrics techniques optimization was studied the behavior of the system in relationship the variables: pH of medium, time and temperature reaction, concentration of the 2,3-diaminonaphthalene, composition of the solvents and addition of sodium dodecilsulfate to the system. In the homogeneous mixtures of the solvents water-ethanol-chloroform or water-ethanol-toluene, denominated of single phase solutions, the aqueous portion introduces the ion Se(IV) and the solvents chloroform and toluene introduce the reagent 2,3-diaminonaphthalene, respectively in their systems. The variables pH, time and temperature were studied with an experimental design 23 to evaluate possible interaction effects among the variables for the method of the analysis of the normal ones. In the system containing chloroform the effect of the interaction pHxTemperature was observed and these varied were optimized by the method of analysis surface response. Already variable time was optimized with classic procedure. For the system containing toluene was not observed interaction effects and all the variables were optimized with the classic procedure. For evaluation of the influence of the composition of the solvents in the sensibility the procedure of experimental design for mixtures was used. In the two studied systems significant influence of the composition of the mixture of the solvents was observed obtaining an increase of sensibility of approximately 50% after the optimization. In the intention of improving the sensibility the possibility of the job of the surfactant sodium dodecilsulfate of was evaluated also in the reaction medium and just the system containing chloroform presented significant earnings of sensibility, approximately 10%. It was obtained curves analytical of calibration and it is observed that both system the development of selenium determination methodology is viable and it should be evaluated the behavior of the probable interferences and means to minimize their effects in the selenium determination, according to matrix chosen.