Simultaneous determination of zirconium and hafnium as ternary complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and fluoride by reversed-phase liquid chromatography

Optimum conditions for the reversed-phase liquid chromatographic (RP-LC) separation of ternary Zr(IV) and Hf(IV) complexes with fluoride (or acetate) and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) performed with the end-capped C18 column were evaluated. The ternary metal systems with fluoride were chosen as a basis for the method for simultaneous determination of Zr(IV) and Hf(IV) ions with use of a mobile phase consisting of acetonitrile/water (55+45, v/v) mixture containing fluoride ion in the concentration of 1.5×10−4 M, pH=4.0. The chelates were detected at 585 nm and the calibration graphs (20 μl of the sample was injected) were linear in the ranges: 1–200 μg l−1 of Hf(IV) and 0.8–160 μg l−1 of Zr(IV). The detection limits were 0.8 μg l−1 and 0.2 μg l−1 for Hf(IV) and Zr(IV), respectively. The applicability of the developed procedure was demonstrated by analyzing ammonium iron(II) sulfate (direct and simultaneous determination of zirconium and hafnium) and hafnium oxide (determination of zirconium) preparations.