Capillary electrophoresis with in-capillary solid-phase extraction sample cleanup.
An in-capillary, solid-phase extraction (SPE)-capillary electrophoresis (CE) method, with not only high preconcentration factor but also no adsorption on the inner capillary wall of absorbing species in real complex samples, has been developed with a hole-opened capillary. The SPE sorbents approximately 3 mm in length was packed in the inlet end of the capillary. A hole approximately 30 microm in diameter was opened after the sorbents on the capillary. Sample solutions were loaded from the inlet end, and the sample wastes flowed out from the hole. After a certain time of the sample loading, a 1.5-mm-long methanol plug was introduced from the inlet end and forced to pass by the sorbents and the hole. Then, a separation voltage was applied between the hole and the outlet end of the capillary to carry out normal CE. When the sample loading time was 120 min, CE peak heights of the 2,4-dichlorophenol and 2,4,5-trichlorophenol were proportional to their concentration in a range of 0.08-5 ng/mL, and their detection limits were 25 and 17 pg/mL, respectively. A 16,000-fold sensitivity enhancement was obtained for CE of the chlorophenols with only a little decrease in CE separation efficiency. It was also demonstrated with the mixture of the chlorophenols and a surfactant cetyltrimethylammonium bromide that the present method could eliminate the adsorption problem of absorbing species on the inner wall during sample loading. Furthermore, the SPE-CE was directly applied to determination of chlorophenols on the level of 0.02 ppb in downstream water of a river, and the results agreed well with those obtained with off-line SPE-HPLC experiments.
Zhang
Luo-Hong
LH
Department of Materials Science and Engineering, Faculty of Engineering, University of Fukui, Fukui, Japan.
Wu
Xing-Zheng
XZ
D000327:Adsorption; D002733:Chlorophenols / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D019075:Electrophoresis, Capillary / Q000379:methods*; D052616:Solid Phase Extraction / Q000379:methods*
D002733:Chlorophenols