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 thiocyanate is proposed. According to this procedure, Mo(VI) is extracted with alpha-benzoinoxime by single-phase extraction in a water/ethanol/chloroform homogeneous ternary solvent system at a nominal pH of 2 and then is spectrophotometrically determined, after separation from the matrix in a similar solvent mixture. The determination is performed by forming a homogeneous phase using the solvent containing the extracted metal as one of the components of the reactional solvent system, eliminating the time-consuming metal complex destruction step. Under these experimental conditions, the calibration graph is linear up to 8.00 mug ml(-1), according to the equation A=0.005+0.143C(Mo(VI)) (r(2)=0.9999). Using the experimental conditions described, the absorbance readings are stable for periods up to 18 h. The interference of the most common interfering species for this method can be prevented by adding Fe(2+) and H(2)PO(4)(-) to the solvent system prior to the extraction step. The accuracy of the proposed method was evaluated by comparing with standard samples determined by atomic absorption measurements with background correction.
Carlos de Andrade
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J
Universidade Estadual de Campinas, Instituto de Quimica, CP6154, 13083-970, Campinas, SP, Brazil.
José Cuelbas
C
C
de Paula Eiras
S
S