Large volume sample stacking in capillary electrophoresis of weakly acidic compounds using coated capillaries at high pH

摘要

Large volume stacking using the electroosmotic flow (EOF) pump (LVSEP) in capillary electrophoresis under a reverse potential is a convenient and straightforward approach for on-lie concentration of dilute anionic sample solutions. LVSEP achieves automatic sample matrix removal and subsequent separation without intermediate polarity switching nor complicated instrumental setup. Since anionic analytes should move against the EOF in LVSEP.EOF needs tobe suppressed. We extended the range of LVSEP up to pH 11 using various EOF suppression methods,such as dynamic coating by polymer pretreatment and permanent coating. Weakly acidic organic compounds (pK_a<5.2),chlorinated phenols (pK_a=7-9),and aromatic aminoacids (pK_a2 ~ 9.3) were concentrated and sepated and separated. Byhydrodynamicallyfilling the whole capillary of 27cm long with the sample solution,fast and reliqable injection was achieved and sensitivigy enhancement factors as large as 170 were readily obtained in less than 8 min.