Differential determination of antimony(III) and antimony(V) by solvent extraction-spectrophotometry with mandelic acid and Malachite Green, based on the difference in reaction rates

Highly sensitive and reproducible extraction-spectrophotometric methods for differential determination of antimony(III) and antimony(V) were investigated. It was found that antimony(III) reacts easily with mandelic acid to form a complex anion extractable into chlorobenzene with Malachite Green from weakly acidic media (pH 2.2-3.5) at room temperature, whereas antimony(V) reacts only slowly, and heating for 15 min at 45 degrees is needed to obtain maximum sensitivity. The significant difference between the rates of reaction of mandelic acid with antimony(III) and antimony(V) was applied to the differential determination of these two species. The calibration graph was linear over the range 0.15-6.0 mug for antimony(III), and 0.20-10 mug for antimony(V).