Reversed-Phase High-Performance Liquid Chromatography for the Determination of 15 Rare Earth Elements in Surface Water Sample Collected in a Mining Area from Lavras do Sul/RS, Brazil

A methodology was developed to assay 15 rare earth elements (REE) (La to Lu and Y) in a surface water sample from a mining area. The samples were collected in the mining area of Lavras do Sul, RS, Brazil. Reversed phase high-performance liquid chromatography employing α-hydroxyisobutyric acid (HIBA), sodium dodecyl sulfate as the ion interaction reagent, and acetonitrile as the organic modifier was used. Analytical detection was performed by spectrophotometry after post-column derivatization with 4-(2-pyridylazo)-resorcinol (PAR). Different chromatographic parameters such as ionic interaction reagent, HIBA concentration, pH, and PAR reagent concentration were studied to achieve the best conditions for the individual separation of REE. The method was validated in terms of the main analytical characteristics (linearity, limits of detection and quantification, precision, interferences, and accuracy). A method for sample cleanup was discussed. Under optimized conditions, it was possible to separate 15 REE (La to Lu and Y) in less than 15 min, with resolution of peaks Y and Dy. The cleanup procedure ensured the selectivity required to determine REE in natural water samples. The accuracy was assessed by regression analysis against measurements by ICP-MS. The calculated quantification limits ranged from 0.07 to 0.48 µg mL−1, for the most sensitive (Dy) to least sensitive (La), respectively.