DETERMINATION OF LANTHANIDES AND YTTRIUM IN HIGH PURITY DYSPROSIUM BY RP-HPLC USING α-HYDROXYISOBUTYRIC ACID AS AN ELUENT

Abstract

An HPLC method is presented for the determination of lanthanides viz. lutetium (Lu), ytterbium (Yb), thulium (Tm), erbium (Er), holmium (Ho), terbium (Tb), and yttrium (Y) in high-purity dysprosium oxide (Dy2O3) matrix. In view of their similar chemical and physical properties, determination of rare-earth elements in bulk of a rare-earth element is a difficult task. Studies were carried out on C18 and C8 reversed phase columns employing α-hydroxyisobutyric acid (α-HIBA) as an eluent. n-Octane was used as an ion interaction reagent (IIR). Different chromatographic parameters e.g., ion interaction reagent, pH and concentration of α-HIBA were studied simultaneously to arrive at the optimum condition for the individual separation of lanthanides. When n-Octane sulphonate was used as the IIR, C8-based stationary phase was found to give significantly better resolution as compared to C18-based stationary phase. Under the optimized conditions, it was possible to resolve Y from Dy using α-HIBA as the single eluent. Separation and quantification of rare-earth elements were possible in samples with Dy/Tb and Dy/Y amount ratios up to 200. The method was validated using the simulated sample containing above lanthanides, Y and Dy matrix. Quantification was done using standard addition method. The method was successfully applied for the quantification of lanthanides and Y in high purity Dy2O3 sample. Concentrations of Lu, Yb, Tm, Er, Ho, Tb, and Y were found to be 74 ppmw, 432 ppmw, 22 ppmw, 57 ppmw, 3325 ppmw, 1207 ppmw, and 4463 ppmw, respectively.