Characterisation of mixed lithium dodecyl sulphate/lithium perfluorooctanesulphonate pseudo‐stationary phases in MEKC

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

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 3.1min from a 70.0mM LPFOS solution to a 67.5mM LDS solution with nearly complete separation within 15min using the simulated parameters.

Recent advances in CE analysis of antibiotics and its use as chiral selectors

Antibiotics are a class of therapeutic molecules widely employed in both human and veterinary medicine. This article reviews the most recent advances in the analysis of antibiotics by CE in pharmaceutical, environmental, food, and biomedical fields. Emphasis is placed on the strategies to increase sensitivity as diverse off-line, in-line, and on-line preconcentration approaches and the use of different detection systems. The use of CE in the microchip format for the analysis of antibiotics is also reviewed in this article. Moreover, since the use of antibiotics as chiral selectors in CE has grown in the last years, a new section devoted to this aspect has been included. This review constitutes an update of previous published reviews and covers the literature published from June 2011 until June 2013.