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Dual opposite injection electrokinetic chromatography: Nonionic microemulsion pseudostationary phase and novel approach to electrokinetic sampling bias
Author(s) -
Zhou Marilyn X.,
Foley Joe P.
Publication year - 2004
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200305738
Subject(s) - electrokinetic phenomena , capillary electrophoresis , chemistry , chromatography , analytical chemistry (journal) , capillary action , micellar electrokinetic chromatography , electrophoresis , elution , microemulsion , phase (matter) , microfluidics , materials science , nanotechnology , pulmonary surfactant , biochemistry , organic chemistry , composite material
Dual opposite injection capillary electrophoresis (DOI‐CE) is a family of CE techniques in which the sample is introduced into both ends of the capillary. For the analysis of compounds with widely varying p K a values using a voltage‐driven separation scheme, DOI‐CE is superior to conventional CE with sample introduction at only one end of the capillary due to DOI‐CE's broader elution window. To enhance the DOI‐CE separation, a running buffer with a microemulsion system was developed. Since DOI‐CE works best under conditions of low electroosmotic flow (EOF), the suppression of EOF via the addition of a multiply charged cation ( e.g. , Zn 2+ ) to the buffer was investigated, and was found to suppress the EOF effectively at moderate concentrations (2.5–10 m M ). Three different dual opposite injection modes were studied: simultaneous electrokinetic injection, sequential electrokinetic injection, and sequential hydrodynamic injection. The injection bias in the first two electrokinetic injection modes was compared with the sequential hydrodynamic injection. Corrections in the bias of the electrokinetic injections were discussed, and an improved approach was suggested. Finally, the effect of the relative concentration of the multiply charged cation in the sample plug and running buffer on the peak shape of co‐electroosmotic and counter‐electroosmotic ions was examined, and found to be much more influential on the latter.