Complexation of molybdenum(VI) and tungsten(VI) with pyrocatechol violet and phenylfluorone on a solid phase

Diffuse reflection spectroscopy is used to study color reactions of tungsten and molybdenum with pyrocatechol violet (PV) and phenylfluorone (PF) on a solid phase of polyacrylonitrile fiber impregnated with AN-31 (PANV-AN-31) or AV-17 (PANV-AV-17) anion exchangers. The relations of the analytical signals of complexes to sorption conditions in the batch mode, such as the acidity of solutions, presence of masking substances, and metal concentration, were found. A system was selected for the sorption-spectroscopy determination of 0.02–0.12 μg/mL of molybdenum in the presence of a fivefold excess of tungsten by sorption on PANV-AV-17 from a boric acid solution with pH 5 and reaction with PF. The sorption on PANVAN-321 from boric acid solutions with pH 3 made possible the determination of the total concentration (0.8–4.2) × 10−6 M of molybdenum and tungsten by the reaction with PV.