A New Spectrophotometric Determination of Chromium (VI) As Cr2O72- After Cloud-Point Extraction using a Laboratory-Made Organic Reagent
A new trend in extraction and preconcentration of chromium (VI) using laboratory-made azo dye reagent 2- [benzenethiazolylazo]-4-benzenenaphthol (BTABN) after cloud-point extraction (CPE) and its determination by spectrophotometrically. The method involved the reaction of Cr2O7 2- with BTABN in acidic medium forming a hydrophobic ion-association complex [HBTABN][HCr2O7] which is entrapped into micelle-mediating solvent (Triton X-100) and the Cr(VI) detected spectrophotometrically at λmax of 475 nm. The effect of the several factors on the CPE efficiency is optimized by one-factor-at-a-time (OFAT). Extensive thermodynamic study has been presented to understand the mechanism of extraction and solubilisation of ion-association complex in micelles. The interferences effect of divers ions is also considered. Under the optimized conditions, enrichment factor of 270 is achieved leading to limit of detection and limit of quantitation of 0.017 and 0.0568 μg mL-1 respectively. The linearity of 0.1-2.0 μg mL- 1 and sensitivity in term of molar absorptivity is 4.47×104 L.mol-1.cm-1 are obtained .The precision (RSD%; n=7) of the proposed method is of 0.31% % at 2.0 μg Cr (VI) mL-1. This method is applied in the determination of Cr (VI) in various environmental and botanical samples.
