Chromatographic separation and determination of some heavy metals and the sum of the rare earth elements in some geological materials

Abstract

An ion chromatographic method for separation and determination of the sum of the rare earth elements in addition to the individual determination of some heavy metal ions has been developed. The separation has been performed on a mixed bed column, IonPac CS5A containing both anion and cation exchange sites. Selective separation of heavy metals was performed by isocratic elution using pyridine-(2,6)-dicarboxylic acid eluent followed by on-line elution of the total rare earth elements using oxalic acid eluent. Post-column spectrophotometric detection with 4-(2-pyridylazo) resorcinol was then coupled at 530 nm. The separation factors of the different ions were found to be dependent on the eluent concentration, the pH and to a much more extent on the flow rate. The optimized developed method has been validated by its application for the analysis of some heavy metals and the sum of the rare earth elements in a sample from Abu Rusheid mineralization that is considered as a reference material and has then been used for the analysis of two other samples represent two different localities one of which is from Gabal Gattar area while the other is from Abu Tartour phosphate deposits. The optimized method enabled the successful determination of both heavy metals and rare earth elements sum within a total analysis time of about 20 min with high reproducibility.