On-line concentration of neutral analytes for micellar electrokinetic chromatography .1. Normal stacking mode

Using two anionic high-molecular-mass surfactants, butyl acrylate-butyl methacrylate-methacrylic acid copolymers, sodium salt (BBMA), and sodium 10-undecylenate (SUA) oligomer, and an anionic low-molecular-mass surfactant, sodium dodecyl sulfate (SDS), almost an order of magnitude improvement in concentration detection limit for a neutral analyte was made feasible by normal stacking mode (NSM). Stacking efficiency and recovery were independent of analyte retention factors and were slightly dependent on the nature of the pseudostationary phases. Furthermore, fundamental conditions for on-line sample concentration by NSM were theoretically and experimentally examined. (C) 1997 Elsevier Science B.V.