Extraction and Spectrophotometric Determination of Molybdenum with o-Hydroxythiophenols and Aromatic Amines

Abstract

The interaction of molybdenum (VI) with o-hydroxythiophenol derivatives (HTPDs) and aromatic amines (AAs) was studied. The following three HTPDs, which contain different halogen atoms at position 5, were used: 2-hydroxy-5-chlorothiophenol(HCTP), 2-hydroxy-5-bromothiophenol (HBTP), 2-hydroxy-5-iodothiophenol (HITP)]. The examined AAs were aniline (An), Nmethylaniline (mAn) and N,N-dimethylaniline (dAn). The obtained ternary complexes have a composition of 1:2:2 {Mo(V):HBTP:AA}.Optimal conditions for their liquid-liquid extraction (LLE) were found: organic solvent (chloroform), pH (4-6), concentration of the reagents ((1.3- 1.5)10^–3moldm^–3 (HTPD) and (1.2-1.5)10^–3moldm^–3 (AA)) and extraction time(colour develops almost immediately after the reagents addition). The absorbance of the extracts is stable for at least 48 hours. The optimum shaking time is 10 min.). Under the optimal conditions, the complexes have absorption maxima (max) at 515-538 nm and molar absorptivities (max) between 3.110⁴dm³mol^–1 cm^–1. The degrees of extraction were 98.4%. The results suggested that linear relationships exist between the spectral characteristics (max or max) and some fundamental properties of the halogen substituent in the HTPD (atomic mass and electronegativity). The effect of foreign ions on the LLE-spectrophotometric determination of molybdenum was examined and two sensitive, selective and precise procedures for molybdenum determination were proposed. The relative standard deviations for Mo content of (3-5)10^–4 % were 4% (HCTP-An procedure) and 3% (HBTP-An procedure).