On-line preconcentration and sample clean-up system for the determination of vanadium as a 4-(2-pyridylazo) resorcinol–hydrogen peroxide ternary complex in plant tissues by ion-interaction high performance liquid chromatography Original Research Article

An HPLC method for the determination of vanadium using on-line preconcentration and sample clean-up has been developed employing a C18 column. 4-(2-Pyridylazo) resorcinol (PAR) and hydrogen peroxide were used as pre-column complexing agents for the determination of vanadium. Aliquots of either standard or sample solutions (100 μL and 2 mL) containing the vanadium complex were loaded onto a guard column (C18, 0.4 mm × 4.6 mm) with a carrier mobile phase comprising 20% (v/v) methanol, 5 mM acetic acid, 5 mM citric acid, l0 mM tetrabutylammonium bromide (TBABr) at pH 7 (eluent 1). A flow rate of 2 mL/min for 0.40 min was used for a 100 μL injection loop, and 1.65 min for the 2 mL injection loop, with the effluent being directed to waste. The vanadium complex was flushed onto the analytical column (C18, 150 mm × 3.9 mm, 4 μm), via an automatic switching valve, using a mobile phase comprising 32% (v/v) methanol, 5 mM acetic acid, 5 mM citric acid, and 5 mM tetrabutylammonium bromide (TBABr) at pH 7, with a flow rate of 1 mL/min for 1.60 min. The switching valve was returned to its original position, and any unwanted species remaining on the guard column were eluted with methanol for 5 min. The guard column was then re-equilibrated with eluent 1 for 5 min before the next injection. The analytes were detected at 540 nm. The detection limits (determined by a signal-to-noise ratio of 3) of vanadium with on-line preconcentration using 2 mL and 100 μL injection loops were 3.1 and 67 ng/kg, respectively.