Mutual Separation of Metal Chelate by Solvent Extraction-Micellar Electrokinetic Capillary Chromatography

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1.Mutual Separation of Metal Ions by Dithizone Extraction-Isotachophoresis on the Basis of HSAB PrincipleBased on the hard and soft acids and bases (HSAB) principle, a method for extraction of metal ions with dithizone was developed for preconcentration and separation of trace metal ions. The extracted metal ions in organic phase were back-extracted to EDTA solution. The resulting solution was applied to isotachophoretic analysis. The separation of zinc (II), cadmium (II) and lead (II) at 10-6 mol dm03 level could performed by the present method.2.Mutual Separation Method for Metal Ions by Solvent Extraction with Diethyldithiocarbamic Acid and Isotachophoresis on the Basis of HSAB Principle.On the basis of the HSAB principle, a method for extraction of metal ions with diethyldithiocarbamic acid (DDTC) consisting of the preconcentration and separation of trace metal ions was developed. Metal ions extracted into CCl_4 were back-extracted into Cu-EDTA solution which was applied to isotachophoretic analysis. This method made possible the separation of Cd^<II>, Fe^<II>, Pb^<II> and Zn^<II> at 10^<-6> mol dm^<-3> level.Back-Extraction Mechansim of Dithizonato Chelate.The back-extraction mechanism of dithizonato Chelate (MR_2, M=Zn, Cd) was studied. And it was found that the rate-determining step is the reaction of MR_2^*+H^**MR^*+HR in the aqueous phase following the rapid partition of MR_2 between the organic and aqueous phase and formation of ring-opened complex (MR_2^*) at the initial stage of shaking.