HYDRIDE GENERATION OPTIMIZATION APPLIED TO As DETERMINATION IN WATER BY MICROWAVE PLASMA-ATOMIC EMISSION SPECTROMETRY.

AZCARATE ROSANA VALERIA; SILVANA MARIELA AZCARATE; CAMIÑA J.M.; SAVIO, M.

Florianopolis

Congreso; 18º ENCONTRO NACIONAL DE QUIMICA ANALITICA; 2016

A highly sensitive and simple method, based on hydride generation and atomic emission detection, for the determination of As in water samples, has been developed. For this purpose, experimental design and optimization techniques were applied in order to optimize the hydride generation atomic emission spectrometry (HG?MPAES) procedure. Multivariate optimization by using the desirability function was used to find experimental conditions where the system generates desirable results. The effects of several factors affecting the hydride generation efficiency -hydrochloric acid (1-20%), sodium tetrahydroborate (0.2-2%), and potassium iodide (0.5-2%) concentrations and flow rates (0.5-10 ml.min-1) - were studied on the As signal intensity (193.695 nm). In addition, parameters affecting the hydride measurement -nebulizer gas pressure (80-240 kPa), viewing position ((-20)-20) - have been also investigated. This latter response was taken into account in order to improve the quality of figures of merit. The ruggedness was evaluated by means of an experimental 2-level fractional factorial design, in which the accuracy was assessed when small changes were set in the studied parameters 1.The As determination was carried out by microwave plasma atomic emission spectrometry (MPAES). Hydride generation was performed by the Multimode Sample Introduction System (MSIS), which uses thin film hydride technology for significantly better performance than conventional nebulization 2,3.Systematic optimization procedures was carried out by selecting an objective function, finding the most important factors and investigating the relationship between responses and factors by the so-called response surface methods (RSM) 4. A central composite design was used, consisting of 30 experiments: combinations of the (selected) independent variables. The accuracy of methods has been verified by using Standard Reference Material 1643e, Trace Elements in Water. The developed method was applied to underground water of La Pampa, Argentina.