Kinetic determination of iodide in pharmaceutical and food samples
Abstract
A kinetic method for the determination of iodide based on its inhibitory effect on the PdII catalysed reaction between ethylenediaminetetraacetic acid (EDTA)–CoIII and the hypophosphite ion is described. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance at 540 nm. Under the optimum experimental conditions of 2.6 × 10–3 mol dm–3 CoIII–EDTA, 0.4 mol dm–3 H2PO2–, pH 3.2 (adjusted with Britton–Robinson buffer), 0.57 µg ml–1 PdII and 20 ± 0.2 °C, iodide was determined in the range 2–28 ng ml–1. The method was applied to the determination of iodide in pharmaceutical products, iodinated salts, cow's milk and infants' powdered milk.