Spectrophotometric determination of molybdenum in biological materials based on flotation of its 3,5-dinitrocatechol complex associated with rhodamine B
Résumé
A flotation-spectrophotometric method for the determination of molybdenum has been developed and its applicability to the analysis of biological materials has been demonstrated. The method is based on the formation of the ion-associate of the anionic 3,5-dinitrocatechol molybdenum complex with rhodamine B. The compound is separated by flotation, washed, and then dissolved in acetone whereupon the absorbance of the resulting solution is measured. Beer's law is obeyed up to a molybdenum concentration of 0.3 μg/ml and the molar absorptivity is 2.1 × 105 liter · mol-1 cm-1 at 555 nm. The molar ratios of the components in the floated and washed compound have been determined and the formula [(RB+)2][MoO2(DNC)2 2-] has been proposed. The method becomes specific after a preliminary separation of molybdenum by its extraction as the α-benzoinoxime complex from 2 M HCl. The accuracy of the method has been demonstrated by determining molybdenum in three certified reference materials. © 1990.