LIQUID-LIQUID EXTRACTION-SPECTROPHOTOMETRIC DETERMINATION OF MOLYBDENUM USING o-HYDROXYTHIOPHENOLS

Abstract

27 liquid-liquid extraction-chromogenic systems containing Mo(VI), o-hydroxythiophenol derivative {HTPDs: 2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP) or 2-hydroxy-5-iodothiophenol (HITP)} and aromatic amine (AA) were studied. Aniline (An), N-methylaniline (mAn), N,N-dimethylaniline (dAn), o-toluidine (o-Tol), m-toluidine (m-Tol), p-toluidine (p-Tol), 3,4-xylidine (o-Xyl), 2,4-xylidine (m-Xyl), and 2,5-xylidine (p-Xyl) were the examined AAs. Optimization experiments for molybdenum extraction-spectrophotometric determination were performed and the following parameters were found for each of the systems: organic solvent (opt), pH (opt), C HTPD (opt), C AA (opt), shaking time (opt), l (max) and e (max). Under the optimum conditions, the molar ratio of the reacting Mo(V), HTPD and AA was 1:2:2 and the degrees of Mo extraction were R³98.4%. Linear relationships involving the spectral characteristics of the extracted complexes (l max or e max ) and some fundamental properties of the halogen substituent in the HTPD were discussed. The effect of foreign ions was examined and two sensitive, selective and precise procedures for extraction-spectrophotometric determination of molybdenum were proposed. The relative standard deviations for Mo content of (3-5)´10 –4 mass % were 4% (HCTP-An procedure) and 3% (HBTP-An procedure).