A bulk liquid membrane–flow injection (BLM–FI) coupled system for the preconcentration and determination of vanadium in saline waters

A bulk liquid membrane–flow injection (BLM–FI) system has been developed for the preconcentration and spectrophotometric determination of vanadium in saline waters. The preconcentration step was based on a bulk liquid membrane containing Aliquat 336 (acting as a carrier) dissolved in dodecane/dodecanol. Vanadium species were chemically pumped due to the pH gradient between the sample (pH 3.2) and the receiving solution (pH 9.8). Vanadium transport through the membrane was monitored by a new and sensitive spectrophotometric method based on its reaction with di-2-pyridyl ketone benzoylhydrazone (dPKBH) in an acidic medium. As a consequence of membrane transport, vanadium was recovered in an ammonium solution, where total vanadium concentration was spectrophotometrically determined at 375 nm, as the pentavalent species, by using a flow injection analysis (FIA) system. Under optimal conditions, this FIA system provided a detection limit of 4.7 μg L−1 (3sblank/m) and RSD 2.72%, for vanadium determination in saline samples. Both preconcentration and determination steps were previously optimized by modified simplex methodologies. oposed coupled method was successfully applied to the determination of vanadium in a certified reference material (TMDA-62) and in two seawater samples.