Theoretical migration model for micellar capillary electrophoresis and itsapplication to the separation of anionic metal complexes of HEDTC and CDTA

A mathematical model relating the effective mobility of an analyte in micel lar capillary electrophoresis (MCE) to the concentration of surfactant and organic modifier in the background electrolyte (BGE) was derived. Effective mobility is expressed in terms of the electrophoretic mobility of the anal yte, the partition coefficient of the analyte into the micelle, and the inf luence of organic modifier on these two factors. The performance of the mod el was evaluated using Cd(II), Pb(II), Co(II), Ni(II), Bi(III), Cu(II), and Hg(II) complexes of bis(2-hydroxyethyl)dithiocarbamate, all of which carry a partial negative charge, and Cd(II), Pb(II), Co(II), Ni(II), Bi(III), Cu (II), Hg(II), Fe(III), Ag(I), Tl(I), and Mn(II) complexes of trans-1,2-diam inocyclohexane-N,N,N',N'-tetracetic acid, all of which are anionic having c harges in the range -1 to -3, These analytes were separated in berate BGEs containing 10-50 mM sodium dodecyl sulfate and 0-20% (V/V) methanol, Nonlin ear regression was used to derive parameters for the model from experimenta l data and these parameters were used to predict effective mobilities of th e analytes.Predicted values of effective mobilities agreed with experimenta l values to within 3.1%. Values of parameters from the model equation are u sed to explain changes in separation selectivity observed at different BGE compositions and the model equation is shown to be applicable to computer-a ssisted optimization of the BGE composition, in MCE using a limited number of experiments.