Determination of vanadium, niobium and tantalum by HPLC using 2-(2-quinotinylazo)-resorcin as pre-column derivatization reagent

A new method for analysis of vanadium, niobium and tantalum as metal chelates of 2-(2-quinolinylazo)-resorcin (QAR) was developed using high performance liquid chromatography. The vanadium, niobium and tantalum ions were pre-column derivatized with QAR to form coloured chelates. The V-QAR, Nb-QAR, Ta-QAR were enriched by solid phase extraction with C-18 cartridge. The enrichment factor of 100 was achieved by eluted the retained chelates from the cartridge with tetrahydrofuran (THF). The chelates were separated on a ZORBAX Stable Bound, 4.6 x 50 mm, 1.8 mu m rapid analytical column with acetonitrile-water (42:58, v/v) containing 0.01 mol L-1 pH 4.5 phosphatic buffer and 0.01 mol L-1 of citrate as mobile phase. The vanadium, niobium and tantalum chelates were separated completely within 2.5 min. The detection limits (S/N=3) of vanadium. niobium and tantalum are 3.2, 3.2 and 3.8 ng L-1, respectively. This method was applied to the determination of vanadium, niobium and tantalum in alloy steel, water and geologic samples with good results.