Evaluation of methods for the determination of total molybdenum and vanadium in foodstuffs using spectrophotometric measurements

Abstract

Spectrophotometric methods for the determination of total molybdenum and vanadium in foodstuffs are described. The procedure involves the destruction of organic material by a modified standard wet-oxidation procedure. Molybdenum is determined on an aliquot of the digest as the extractable toluene-3,4-dithiolate complex. Vanadium is determined directly on a smaller aliquot of digest by its catalytic effect on the oxidation of gallic acid with peroxymonosulphuric acid. The optimum conditions for the suppression of direct interferences from other elemental species are described. Molar absorptivities of 2.2 × 10⁴ and 2.0 × 10⁵ l mol^–1 cm^–1 apply to molybdenum and vanadium, as measured, respectively. The accuracy of the total procedure for each element has been assessed by recovery from foodstuff homogenates and, where possible, the accuracy in application to foodstuffs considered by reference to values in standard reference materials. Standard deviations of results for levels normally found in foodstuffs have been calculated and derived confidence intervals and limits of detection are given for each element.