Spectrophotometric determination of molybdenum in vegetal tissues, soils and pharmaceutical compounds with mandelohydroxamic acid

Abstract

Molybdenum was determined spectrophotometrically as an ion associate, formed between the anionic complex [Mo^VIO₂(MHA)Cl₂]^–(MHA = mandelohydroxamic acid) and the methyltrioctylammonium (MTOA) cation, extracted into toluene. The absorbance of the yellow toluene solution was measured at 375 nm. The apparent molar absorptivity is 1.62 × 10⁴ l mol^–1 cm^–1. For the determination of 2.5 p.p.m. of Mo^VI the relative error is 0.5%. The detection limit is 0.05 µg ml^–1 of Mo^VI. The extraction of the mixed ligand complex, MoO₂(MHA)Cl₂(MTOA) is discussed. The proposed method was applied to the determination of Mo in vegetal tissues, soils and pharmaceutical compounds.