Determination of zinc in environmental samples by solid phase spectrophotometry: Optimization and validation study

A simple and specific solid-phase spectrophotometric (SPS) determination of zinc in mu g 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 experimental 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 quantification limits, precision, robustness and selectivity, using suitable chemometric techniques; the trueness was confirmed on environmental samples (water and milk).