Spectrophotometric determination of cadmium (II) with 1-(2-pyridylazo)-2-naphthol after Capriquat extraction

Abstract

The procedure for the determination of cadmium (II) in the presence of large amounts of zinc (II) is as follows: Take a sample solution containing 0100 μg of cadmium (II) in a separatory funnel. After the addition of 10 ml of 10% thiourea solution and 5 ml of 20% potassium iodide solution, adjust the pH to 5.8 by adding 5 ml of 5% urotropine solution. The resulting volume should be ca. 50 ml. Add 20.0 ml of 5% Capriquat in chloroform, and then shake the mixture for 3 min. Transfer the organic phase to another separatory funnel, and repeat the extraction with 20.0 ml of the Capriquat solution. Wash the aqueous phase with 10.0 ml of pure chloroform. Combine the extracts and backextract zinc (II) twice with 20 ml of 10% potassium nitrate solution, then add 5 ml of 0.1% 1-(2-pyridylazo)-2-naphthol in methanol, 10 ml of 10% ammonium nitrate solution and allow the phases to separate. Measure the absorbance of the organic phase at 555 nm against a reagent blank. The calibration curve was linear over the concentration range of 0100μg cadmium (II) /50 ml, the Sandell sensitivity being 0.0044 μg/cm². The effect of diverse ions was also investigated. Almost all metal ions did not interfere with the determination. The present method was applied to the determination of trace amount of cadmium in high purity metallic zinc.