PAR Photometric Determination of Trace Amounts of Cadmium After Separation and Enrichment from PVA-H2O-Acetone System

Based on the difference of solubility of the complex of Cd(Ⅱ) with polyvinylalcohol (PVA) in water and in acetone,a method for separation and enrichment of trace amounts of Cd2+-ion was proposed.In a solution of pH 3-10,a water soluble complex was formed between Cd2+-ion and PVA,which was insoluble in acetone and separated out upon addition of sufficient amount of acetone (≥25 mL).Saturated solution of KCl (1.0 mL) was added as salting-out agent in the precipitation.Precipitate of Cd2+-PVA was separated from the solution by decantation,dissolved in a small volume of water and determined photometrically with PAR as color reagent.Linear relationship between values of absorbance and concentration of Cd2+-ion was obtained in the range of 5-2 000 μg·L-1.Detection limit (3s/b) of the method found was 2 μg·L-1.In the determination of cadmium in water samples,the results found by this method were checked quite well with the results obtained by FAAS.Values of recovery obtained by standard addition method were in the range of 96.3%-98.0%.A brief discussion on the mechanism of the precipitation process was also given.