Reversed-phase high-performance liquid chromatographic separation of niobium(V) and tantalum(V) by pre-column chelation with 4-(2-pyridylazo)resorcinol

Abstract

Niobium(V) and Ta^V were separated and determined by reversed-phase high-performance liquid chromatography with spectrophotometric detection at 540 nm. 4-(2-Pyridylazo)resorcinol (PAR) was used as a pre-column chelating agent. The optimum conditions for the determination of these trace metal ions, including the concentration of the buffer, the pH of the chelating medium and the eluent, the concentration of PAR, the time required for colour development and the composition of the eluent, were investigated. The metal–PAR chelates were eluted in 10 min with a mobile phase of methanol–water (30 + 70) containing 1.255 × 10^–2 mol dm^–3 tartrate buffer (pH 6.5). The proposed method was applied to the determination of Nb^V and Ta^V in a relatively complex substance, viz., a nickel-based alloy. The precision and accuracy of the chromatographic method were evaluated.