Stepwise elusion method in micellar electrokinetic chromatography via sequential use of lithium perfluorooctadecyl sulfonate and lithium dodecyl sulfate

摘要

An effective stepwise micellar electrokinetic chromatography (MEKC) elution method was developed using lithium perfluorooctadecyl sulfonate (LPFOS) and lithium dodecyl sulfate (LDS). The hydrogen-bonding property of LPFOS micelles differs from that of LDS micelles, which leads to remarkably different selectivity in the transfer of solutes to the micelles. The present stepwise method is performed by replacing the inlet reservoir of a first running solution containing LPFOS with that of a second running solution containing LDS during a single separation run in the absence of electroosmotic flow under acidic conditions, where LPFOS micelles work as carriers in first and then LDS micelles turn over. Effective separation of 15 nonionic aromatic compounds was controlled well by adjusting the time in the inlet reservoir, which could not be accomplished with systems using only LPFOS or only LDS, with significant changes in the elution order where necessary. Furthermore, separations with the present stepwise method were easily simulated, and the replacement time was optimized for 3.1 min from a 70.0 mM LPFOS solution to a 67.5 mM LDS solution with nearly complete separation within 15 min using the simulated parameters.