Investigations on the behaviuor of Tellurium (IV) and Selenium (IV) in ion-exchange chromatography

For the development of an on-column chromatographic method for the simultaneous separation and detection of selenium(IV) and tellurium(IV), their chromatographic behaviours on cation and anion exchangers as well as on multiphase cation- and anion-exchange/reversed-phase columns, have been investigated. The eluent medium consisted of diluted hydrochloric acid at different concentrations and flow-rates. The detection of selenium(IV) and tellurium(IV) was based on post-column derivatization, of the eluted species, with 1,1,3,3-tetramethylthiourea (TMTU). The TMTU concentration, pH and flow-rate was optimized in order to obtain the best sensitivity for both the analytes. The capacity factor value, k', as well as the charge of the species eluted on the different columns tested, have been obtained for all experimental conditions. It has been demonstrated that the on-column chromatographic separation between selenium(IV) and tellurium(IV) is achievable by exploiting their different elution patterns on ion exchangers. On the basis of peak symmetry and analyte resolution at different concentration ratios, the cation-exchange mode was chosen. Injecting 50 ul of samples, detection limits of 78 and 83 ug/1 for tellurium and selenium, respectively were obtained. Concentrations lower than 10 txg/1 could be determined by increasing the injection volume or by means of on-line preconcentration.