Extraction with 8-quinolinol and mixed anionic additives using ultrasonic irradiation for the catalytic determination of vanadium in freshwaters

Solvent extraction with 8-quinolinol (QN) has been markedly improved by the combined application of ultrasonic irradiation and mixed additives and used for the catalytic determination of vanadium with chlorpromazine in the presence of tartrate. Vanadium in an acidified sample up to 200 ml is extracted twice at pH 3.9–4.3 into two 10-ml portions of CHCl3 with 0.14 M QN, and then back-extracted at pH 11 into 10 ml of 0.01 M NaOH solution. Each extraction time is 10 min. In the back-extraction, recovery of vanadium over 95% was performed by the addition of a mixed solution of KBr, NaBrO3 and HNO3 to the sample and the application of ultrasonic irradiation for 10 (or 5) min. On the other hand, a conventional mechanical shaking without the mixed solution required 60 min for 91% recovery. The proposed method was able to separate vanadium from Ca(II), Mg(II), Al(III), Fe(III), Cu(II), Cr(VI) and NO−2, and has been successfully applied to the determination of vanadium in river and tap waters. The detection limit of vanadium was about 0.03 μg l−1.