Abstract
A simple and highly sensitive extraction—spectrophotometric determination of cadmium is described. The ion-associate formed between the cadmium-PAR anionic chelate and cetyldimethylbenzylammonium chloride (CDBA) is extracted with chloroform at pH 10. The absorption maximum of the extracted species occurs at 505 nm, the molar absorptivity being (9.82 ± 0.30) × 10 4 l mol -1 cm -1. The optimal concentration range for measurements is 0.2–1.0 μg Cd ml -1; Beer's law is obeyed. The composition of the ion-associate is estimated to be CdPAR 2-2CDBA. The conditional extraction constant is log K' ex ≈ 8. The stability constant of the cadmium—PAR chelate in aqueous solution is log β 2 = 17.5 ± 0.3. Extraction with N-benzoyl-N-phenylhydroxylamine is used to avoid several interferences. Moderate amounts of zinc are masked with sodium hydroxide.
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