Capillary Electrophoresis with In-Capillary Solid-Phase Extraction Sample Cleanup

Abstract

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.

Capillary Electrophoresis in Bioanalysis

“…This increases the possibility of contaminants adsorption to the walls of the separation capillary, a problem that has been overcome with the use of a holeopened capillary (46). A small hole, 30 μm, was opened in the capillary wall after the sorbent material of the preconcentrator.…”

On-capillary Chemiluminescence Detection for Capillary Electrophoresis with a Single Capillary

“…With the use of a Q-switched Nd:YAG pulse laser (frequency of 1 Hz, output power of 32 mW, Continuum, CA, USA), a hole (about 30 μm in diameter) was made on the capillary wall at about 50.5 cm from the inlet end by methods similar to those we reported. 34 The hole was fixed in a reservoir (middle reservoir in Fig. 1).…”

On-line combination of monolithic immobilized pH gradient-based capillary isoelectric focusing and capillary zone electrophoresis via a partially etched porous interface for protein analysis

“…Capillary interfaces made by above methods were easy to break from the etched section. Zhang et al [19] used a hole-opened capillary for in-capillary SPE-CE concentration of chlorophenols. In this study, the idea of hole-opened capillary was applied with minor modifications, with the polyimide coating wall of capillary partially removed.…”