Unlimited-Volume Electrokinetic Stacking Injection in Sweeping Capillary Electrophoresis Using a Cationic Surfactant

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• 作者：Maojun Gong ; Kenneth R. Wehmeyer ; Patrick A. Limbach ; William R. Heineman
• 刊名：Analytical Chemistry
• 出版年：2006
• 出版时间：September 1, 2006
• 年：2006
• 卷：78
• 期：17
• 页码：6035 - 6042
• 全文大小：130K
• 年卷期：v.78,no.17(September 1, 2006)
• ISSN：1520-6882

文摘

Sweeping is an effective and convenient way for onlinesample preconcentration in micellar electrokinetic chromatography. The usual procedure includes a hydrodynamic injection step carried out by applying pressureto the sample vial followed by the subsequent sweepingand separation processes. The injected sample volume islimited by the dimensions of the capillary because a partof the capillary has to be left free of sample solution forthe subsequent sweeping and separation steps. In addition, when a short capillary, such as 4-10 cm, is usedfor sweeping, the injected sample volume is small even ifthe entire capillary is filled with sample solution. To solvethis problem, an electrokinetic stacking injection (EKSI)scheme was developed by using a cationic surfactant,dodecyltrimethylammonium bromide, for sweeping incapillary electrophoresis. An experimental model wasproposed, and the entire process was theoretically analyzed. According to the theoretical discussion, the optimalconditions for two model analytes, 5-carboxyfluorescein(5-FAM) and sodium fluorescein (FL), were experimentally determined. The injected sample plug lengths for5-FAM and FL under 20.1 kV for 60 min were experimentally estimated as 836 and 729 cm, correspondingto 28- and 24-fold the effective capillary length, respectively. The EKSI scheme resulted in increased detectionfactors for 5-FAM and FL of 4.5 × 10³ and 4.0 × 10³using 60-min injection relative to a traditional pressureinjection.