Extraction-Spectrophotometric Determination of Chromium(VI) with O, O′-Dibutyl Dithiophosphate1

抄録

Chromium(VI) reacts with O, O′-dibutyl dithiophosphate ion to form tris(dibutyl dithiophosphato)chromium(III) and tetrabutyl thiophosphoryl disulfide in an acidic solution (pH 1.2-1.7). Both of the products are extracted into hexane and the absorbance at 278nm based on these products is utilized for the determination of chromium(VI). The chromium(III) complex corresponding to two-thirds of the initial chromium(VI) concentration and the disulfide corresponding to three-halves of the initial chromium(VI) concentration are extracted under the optimum conditions. The calibration graph obtained is linear over the range of 2×10^-6-1×10^-4mol/dm³ chromium(VI) concentration, and the apparent molar absorptivity (absorbance per initial chromium(VI) concentration in aqueous phase) is 1.69×10⁴mol^-1 dm³ cm^-1. This method is subject to interference from Cu^II, Fe^II, Cd^II, Pb^II, Hg^II, Pd^II, Sn^IV, Sb^III, Se^IV, Au^III, nitrite, sulfite, thiosulfate and ascorbic acid. This method was applied to the determination of chromium in steel samples, and good results were obtained.