Application of electrokinetic supercharging capillary zone electrophoresis to rare-earth ore samples

Capillary zone electrophoresis (CZE) using electrokinetic injection (EKI) with transient isotachophoresis, which was named “electrokinetic supercharging-CZE ” (EKS-CZE), was applied to model samples of rare-earth ores (xenotime and monazite) and a real sample of monazite ore, the abundance of the components being greatly different among samples. When simple EKI was applied, separation and detection of rare-earth ions with smaller mobilities than the major component became difficult with an increase of the content of the major component. In contrast, when EKS-CZE was applied, the minor components (Er, Tm, Yb) with contents less than 0.025% (rare-earth/total rare-earth) could be analyzed. The analytical results for minor components in monazite ore agreed with those obtained by isotachophoresis–particle-induced X-ray emission (ITP–PIXE) and inductively coupled plasma atomic emission spectrometry (ICP-AES) with errors less than 17%. The sample amount required for analysis was 9 μg which is 200-fold smaller than that used in ITP-PIXE analysis. Analytical sensitivity of EKS-CZE was comparable with that of ICP-AES.