Two-Steps Cloud Point Extraction-Spectrophotomtric Method for Separation, Pre-concentration and Determination of V (IV) and V (V) Ions in Real Samples Using Laboratory-Made Organic Reagents

Abstract

Aims: To establish a new analytical method for the extraction and pre-concentration of V (IV) and V (V) species in real samples by cloud point extraction (CPE) coupled with spectrophotometry using two newly laboratory-made chelating reagents. Study Design: All factors affecting the extraction and determination of V (IV) and V (V) ions using micelle-mediation extraction were executed via a classical optimization. In addition the interferences study is also considered. Place and Duration of Study: Department of Chemistry, College of Science for Women, University of Baghdad, Baghdad, Iraq in cooperation with Department of Chemistry, College of Science, University of Al-Qadisiya, Diwanya, Al-Qadisiya, Iraq between April 2014 and November 2014. Methodology: The approach is based on sequential separation of two vanadium species in the same solution. First, the complexation of vanadium (IV) with 2-[(Benzo imidazolyl) azo]-4-benzyl phenol (BIABP) at pH 3.0 and then extracted into micelle phase. Second, the vanadium (V) remaining in aqueous phase after the separation of (IV) is complexed with 2-[2-(5-Nitro thiazolyl) azo]-8 hydroxyquinoline (5-NTA8HQ) and H2O2 in acidic medium to form a ternary complex (V(V)-H2O2-NTA8HQ) which being re-extracted into micelle phase of Triton X-114. The extracted complexes in cloud point layer are dissolved in a minimum amount of ethanolic 0.1 M HNO3, then V (IV) and V (V) are determined spectrophotometrically at their respective absorption maxima. The proposed method was applied to the estimation of the two vanadium species in various real samples with satisfactory results where the method detection limit in these matrices was of 0.120 and 0.037 µg g-1 for V (IV) and V (V) respectively. Results: At established optimized conditions, a 159 and 99 fold enrichment factors and linear range of 10-100 and 1-70 ng mL-1, leading the  limits of detection of 1.78  and 0.75 ng mL-1 for V (IV) and V (V) ions respectively to be achieved in aqueous solution. The average percent recovery of 98.3±0.7 and 97.6±0.4 and a precision (RSD%, n=8) of 0.67% and 0.46%, at 40 and 30 ng mL-1 for V (IV) and V (V) are obtained. Conclusion: The described method is sensitive, easy to apply and interferences-free and in that way the determination of vanadium species in different samples was easily achieved. The results of the established method were compared statistically with ETA-AAS using t-paired test showing no significant difference at 95% confidence interval and the proposed method gave comparable analytical figures of merit compared with other sophisticated techniques.