SPECTROPHOTOMETRIC DETERMINATION OF MO(VI) IN STEEL USING A HOMOGENEOUS TERNARY SOLVENT SYSTEM AFTER SINGLE-PHASE EXTRACTION

An alternative procedure for the determination of Mo(VI) with thiocyan ate is proposed. According to this procedure, Mo(VI) is extracted with alpha-benzoinoxime by single-phase extraction in a water/ethanol/chlo roform homogeneous ternary solvent system at a nominal pH of 2 and the n is spectrophotometrically determined, after separation from the matr ix in a similar solvent mixture. The determination is performed by for ming a homogeneous phase using the solvent containing the extracted me tal as one of the components of the reactional solvent system, elimina ting the time-consuming metal complex destruction step. Under these ex perimental conditions, the calibration graph is linear up to 8.00 mu g ml(-1), according to the equation A = 0.005 + 0.143 C-Mo(VI) (r(2) = 0.9999). Using the experimental conditions described, the absorbance r eadings are stable for periods up to 18 h. The interference of the mos t common interfering species for this method can be prevented by addin g Fe2+ and H2PO4- to the solvent system prior to the extraction step. The accuracy of the proposed method was evaluated by comparing with st andard samples determined by atomic absorption measurements with backg round correction. (C) 1998 Elsevier Science B.V. All rights reserved.