Highly sensitive and highly accurate analysis by capillary electrophoresis

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An on-line preconcentration method utilizing transient isotachophoresis with electrokinetic injection for capillary zone electrophoresis (CZE) and microchip electrophoresis (MCE) was studied by means of computer simulation and experiments. Consequently it was found that this preconcentration method was very useful to realize highly sensitive and highly accurate analysis by CE and MCE, and named as electokinetic supercharging (EKS). Simulational results could be utilized efficiently for optimizing experimental conditions of EKS : The important points were appropriate selection of the leading electrolyte and the terminating one and their molar amount introduced to the separation system depending on the mobility of sample components and the sample amount. Existence of electroosmotic flow(EOF) was not favorable for preconcentration and it should be suppressed for better preconcentration efficiency. Confirming these simulational results by experiments, we achieved LOD of sub-ppb level for ions of alkaline metals, alkaline earth metals and rare-earth elements by EKS-CE, which is comparable with IC and ICP-AES. The proposed transient isotachophoretic method could be applied to e.g. river water with low ionic strength and also to e.g. seawater with high ionic strength. Analysis of iodide and iodate in seawater is a good example of the latter case. The method is also applicable to MCE : We could obtain LOD of 20 times as small as that of usual method (pinched injection) for the analysis of DNA fragments and proteins by EKS-MCE. These results were published in J.Chromatogr. and Electrophoresis and higly evaluated. A patent related to the proposed method ォ病s applied through JST