Flow-Injection Solid Phase Partial Least-Squares Spectrophotometric Simultaneous Determination of Iron, Nickel and Zinc

Abstract

IntroductionSolid phase spectrophotometry (SPS) provides effective methods to combine metal ion preconcentration and their spectrophotometric determination, by integrating the formation of colored complexes and their fixation on the surface of a solid support placed inside the measurement cell.1,2 The coupling between flow injection analysis (FIA) and SPS (FI-SPS) makes it unnecessary to reach equilibrium conditions, thus providing faster and more selective methods than those found in batch conditions. Additionally, it offers a simple and easy way of automation and provides low detection limits, small amounts of samples and reagents 3 being employed. Since flow injection analysis was introduced, the simultaneous determination of several analytes in a same sample has been a challenge in order to make FIA competitive with other analytical techniques. In this way, the use of SPS and FIA has been applied in several studies for the determination of binary mixtures of metal ions, [4][5][6][7] amines 8 and mixtures of dyes. 9-11Approaches employed for multicomponent determination in solution can be also applied in FI-SPS. Flow-Injection Solid Phase Partial Least-Squares Spectrophotometric SimultaneousDetermination of Iron, Nickel and Zinc Um método de calibração multivariada PLS-2 foi desenvolvido para a determinação simultânea de ferro, níquel e zinco em misturas ternárias utilizando a espectrofotometria em fase sólida acoplada à análise em fluxo. Fe(II), Ni(II) e Zn(II) formam complexos coloridos com 1-(2-tiazolilazo)-2-naftol (TAN), imobilizado em sílica funcionalizada C18 em pH 6,4. O procedimento proposto foi baseado nas diferentes razões de reação/retenção dos íons estudados sobre o suporte sólido. Os dados espectrofotométricos dos analitos, fixados no suporte sólido, foram obtidos entre 400 e 800 nm como função do tempo e um algoritmo utilizando o método dos mínimos quadrados parciais (PLS-2) foi usado para prever a concentração dessas espécies em amostras sintéticas. O lote de calibração empregado foi constituído por 8 misturas ternárias e um branco. Misturas contendo 0,040 a 0,20 mg L -1 , de cada espécie, foram resolvidas satisfatoriamente, usando 3 fatores para cada analito com dados espectrofotométricos obtidos em uma faixa de comprimento de onda entre 560 e 650 nm.A PLS-2 multivariate calibration method has been developed for the simultaneous determination of iron, nickel and zinc in ternary mixtures by solid phase spectrophotometry associated with flow injection analysis. Fe(II), Ni(II) and Zn(II) form color complexes with 1-(2-thiazolylazo)-2-naphthol (TAN), immobilized on a C18 bonded silica support, at pH 6.4. The proposed procedure is based on the different reaction/retention ratios of the studied ions on the solid support. Bilinear spectrophotometric data of the analytes, fixed in the solid support, were recorded in the 400-800 nm wavelength range as a function of time and a partial least squares (PLS-2) algorithm was used to predict results of synthetic samples. The calibration set employed was inte...

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