Cloud Point Extraction and Micro Amount Determination of Cadmium as Chloro Anion Complex in Real Samples by using Molecular Spectrophotometry

Abstract

A new procedure for the separation, preconcentration and determination of cadmium as a chloro anion was presented by using the combined cloud point extraction (CPE) methodology and molecular spectrophotometry. The extraction process involved the conversion of cadmium (II) ion in acidic aqueous solution into chloro anion [CdCl₄]^2-complex and subsequently the hydrophobic ion-pair complex formed with crystal violet (CV) cation was extracted into the nonionic surfactant (Triton X-100) rich phase at a temperature above its cloud point (CPT). After phase separation, the surfactant-rich phase was diluted with ethanol and cadmium (II) ion determined by UV-Vis spectromphotometric technique at λ_max of 449 nm. The optimization of complexation and extraction conditions was investigated. Thermodynamic parameters of CPE for solubilization process of the ion-pair complex in Triton X-100 were also considered. Under the optimized conditions, the preconcentration of a 10 mL sample gave preconcentration and enrichment factors were of 125 and 150 respectively. The calibration graph was linear in the range of 0.25-5 μg mL^-1 with a correlation coefficient of 0.9995 and limit of detection of 0.042 µg mL^−1. The relative standard deviation for replicate determinations at (3) µg mL^−1 level was of 2.68%. The proposed method was applied for the determination of cadmium in soil, vegeTables, plant leaves and water which gave satisfactory results relative to results obtain by AAS method

 

Keywords: Cadmium chloro anion, Crystal violet cation, Triton X-100, Cloud point extraction, Spectrophotometry.