title: Double sample preconcentration by in-line coupled large volume single drop microextraction and sweeping in capillary electrophoresis.
abstract: Single drop microextraction (SDME) is a convenient and powerful preconcentration method for CE before injection. By simple combination of sample-handling sequences without modification of the CE apparatus, a drop of an aqueous acceptor phase covered with a thin organic layer was formed at the tip of a capillary; 10 min SDME of fluorescein and 6-carboxyfluorescein from a donor phase of pH 1 to an acceptor phase of pH 9 provided 110-fold enrichments without stirring the donor phase. To improve the concentration effect further, SDME was coupled with an on-line (after injection) sample preconcentration method, sweeping, in which analytes in a long sample zone are accumulated at the boundary of a pseudostationary phase penetrating into the sample zone. It is thus necessary to inject a sample of much larger volume than that of a drop in typical SDME. A Teflon sleeve over the capillary inlet allowed a large volume drop to be held stably during extraction. By in-line coupling 10 min SDME and sweeping of a 30 nL sample using a cationic surfactant dodecyltrimethylammonium, enrichment factors of the double preconcentration were increased up to 32,000.
authors.affiliation: Department of Chemistry, Seoul National University, Seoul, Korea.
authors.forename: Guodong
authors.initials: G
authors.lastname: Liang
authors.forename: Kihwan
authors.initials: K
authors.lastname: Choi
authors.forename: Doo Soo
authors.initials: DS
authors.lastname: Chung
mesh_terms: D005591:Chemical Fractionation / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D019793:Fluorescein / Q000737:chemistry; D005452:Fluoresceins / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008832:Microchemistry / Q000379:methods; D000644:Quaternary Ammonium Compounds / Q000737:chemistry
chemical_list: D005452:Fluoresceins; D000644:Quaternary Ammonium Compounds; C024098:6-carboxyfluorescein; C022806:dodecyltrimethylammonium; D019793:Fluorescein