Determination of molybdate in environmental water by ion chromatography coupled with a preconcentration method employing a selective chelating resin

A simple and sensitive suppressed ion chromatography (IC) method with conductivity detection for the determination of molybdate in environmental water is proposed. Molybdate in highly saline water was extracted and precocentrated. Preconcentration was accomplished by using a chelating resin using a chelating resin immobilized with carboxymethylated polyethylenimine (Presep® PolyChelate). This resin is able to trap a variety of metal elements without any interference of alkali and alkaline-earth metals. A 30-mL volume of brackish water was adjusted for appropriate pH and then flushed through 100 mg of the chelating resin. Molybdate concentrated on the resin could be easily eluted with 6 mL of 0.1 M NaOH. A large volume injection method for IC was achieved with in-line neutralization of the effluent. The determination of 0.6 μg L-1 molybdate in highly saline water was made possible with a 500-μL injection. Samples of brackish water were taken at various distances from the river mouth. The determined concenctrations of molybdate correlated closely with concentrations of chloride.