Pyrogallol red and bromopyrogallol red in new optical methods for the determination of molybdenum(VI) and tungsten(VI)

The complexation of molybdenum(VI) and tungsten(VI) with pyrogallol red (PR) and bromopyrogallol red (BPR) in the presence of a cationic surfactant, cetylpyridiniurn bromide was studied. Conditions of the preconcentration of molybdenum(VI) and tungsten(VI) as complexes with PR and BPR on Silochrom S-120 were found. The concentration coefficients were no lower than 67 for a volume of the aqueous phase of 20 mL and a mass of the sorbent of 0.3 g. Chromaticity characteristics of the complexes in solutions and on the sorbent were determined. It was demonstrated that the complex of molybdenum(VI) with BPR in the presence of cetylpyridinium bromide should be used in the analysis of materials with low concentrations of molybdenum.