Predefine resolution of enantiomers in partial filling capillary electrophoresis and two discontinuous function plugs...

In common partial filling CE (PF-CE), the capillary contains the selectors plug between the injection and detector end to avoid the selector going into the detector zone. To expand this method, we propose a mode of two discontinuous function plugs coupling in-capillary, named as plug-plug PF-CE (ppPF-CE). Initially, we present the method to predefine the effective length of chiral selector to meet the requirement of enantiomers' resolution, which could avoid some experimental procedures. With α-CD as a chiral selector, a satisfactory resolution of enantiomers d,l-tryptophan and d,l-tyrosine was obtained with a partial filling α-CD plug of optimal length and concentration. Subsequently, a second plug containing hydroxypropyl methylcellulose, organic solvents (acetonitrile and methanol), anionic and cationic surfactants (SDS and CTAB), and different concentrations of sodium phosphate buffer was inserted after the selector plug. Effects of plug-plug filling on enantiomers' migration and resolution are discussed. The ppPF-CE might be a new flexible mode for CE application.