Molybdophosphate Complexes Research Articles

The spectrofluorimetric determination of orthophosphate as quinine molybdophosphate

Between 0·02 and 1·2 µg of phosphorus is determined as orthophosphate via the formation of a complex between a molybdophosphate and the alkaloid quinine. Quinine molybdophosphate is precipitated in 0·5 M sulphuric acid, the excess of quinine reagent is removed by washing the precipitate with 0·5 M sulphuric acid, and the complex is dissolved in the solvent mixture acetone-0·5 M sulphuric acid (9 + 1 v/v). The fluorescence intensity of this solution is measured at 445 nm with excitation at 352 nm. Optimum conditions for the determination have been established, and the effects of 100-fold weight excesses of each of thirty-eight foreign ions have been examined. The determination is selective; large amounts of silicate do not interfere, and arsenic(III) and tungsten(VI) are tolerated at 20 and 50-fold weight excesses, respectively. The nature of the quinine molybdophosphate complex has been examined.

A study of pyridinium ternary molybdophosphate complexes: Collection of trace amounts of titanium(IV). zirconium(IV), and thorium(IV)

Trace amounts of titanium(IV), zirconium(IV), and thoriuin(IV) can be quantitatively collected from pyridinium solutions at pH 1–3 with the molybdophosphate complex.The metal ions react with molybdophosphate, and are then precipitated as the pyridinium ternary heteropoly salts. These salts were investigated by infrared spectrophotometry and thermogravimetric techniques.