Analytical Sciences

Determination of Zinc in Environmental Samples by Solid Phase Spectrophotometry: Optimization and Validation Study

M a Francisca MOLINA, Mounir NECHAR and Juan M. BOSQUE-SENDRA *

Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Fuentenueva, s/n, 18071 Granada, Spain

A simple and specific solid-phase spectrophotometric (SPS) determination of zinc in mg dm -3 level has been developed based on the reaction of Zn(II) with 4-(2-pyridylazo)resorcinol (PAR) in the presence of potassium iodide; the product was then fixed on an anionic exchanger. The absorbance of the gel, packed in a 1 mm cell, is measured directly. PAR and KI concentrations were optimized simultaneously using response surface methodology (RSM) from sequential exper-imental Doehlert designs. The advantages of this methodology are discussed, as opposed to univariate optimization, which is also used. The method was validated by obtaining the performance characteristics: linearity, detection and quan-tification limits, precision, robustness and selectivity, using suitable chemometric techniques; the trueness was confirmed on environmental samples (water and milk) (Keywords: Optimization, Doehlert design, method validation, zinc, solid-phase spectrophotometry, 4-(2-pyridyl-azo) resorcinol, Sephadex QAE)

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