Homogeneous liquid-liquid extraction method for the selective separation and preconcentration of ultra trace molybdenum

A new simple and efficient homogeneous liquid-liquid extraction method for the selective separation and preconcentration of molybdenyl ions was developed. a-Benzoin oxime (ABO) was investigated as a complexing ligand, and perfluorooctanoate ion (PFOA(-)) was applied as a phase-separator agent under strongly acidic conditions. Under the optimal conditions ([ABO] = 2.1 x 10(-3) M, [PFOA-] = 1.8 x 10(-2) M, [HNO3] = 1.7 M, [acetone] = 11.8 % (v/v)), 10 mu g of molybdenum in 5 ml aqueous phase could be extracted quantitatively into 40 mu l of the sedimented phase. The maximum concentration factor was 125-fold. Thiocyanate was applied as a chromogenic reagent for the direct spectrophotometric determination of molybdenum in the sedimented phase. The reproducibility of the proposed method is at the most 2.4 %. The influence of the type and concentration of acid solution, the concentration of ABO, the type and volume of the water-miscible organic solvent, the concentration of PFOA-, and the effect of different diverse ions on the extraction and determination of molybdenum(VI) were investigated. The proposed method was applied to the extraction and determination of molybdenum(VI) in natural water, Spinach, and Lucerne samples. A satisfactory agreement exists between the results obtained by the proposed method and those reported by GF-AAS. (c) 2004 Elsevier B.V. All rights reserved.