Spectrophotometric Determination of Antimony (III) By Solvent Extraction with Mandelic Acid and Malachite Green

A sensitive and selective method has been developed for the spectrophotometric determination of antimony in the tervalent oxidation state. It was found that antimony (III) reacts with mandelic acid to form a complex anion extractable into chlorobenzene with malachite green in weak acidic media (pH 2.2 to 3.5) at room temperature and is determined indirectly by measuring the absorbance of malachite green in the extract at 628 nm. The calibration graph is linear for antimony (III) over the range 0.088–1.8 mg 1−1 (7.2 × 10−7–1.5 × 10−5 mol 1−1) with the apparent molar absorptivity ε × 6.9 × 104 1 mol−1 cm−1. Antimony (V) was slightly extracted in the presence of phosphate buffer with ε × 2.7 × 103 1 mol−1 cm−1.