In-capillary solid-phase extraction-capillary electrophoresis for the determination of chlorophenols in water

A novel CE method combined with SPE in a single capillary was developed for analysis of chlorophenols in water. A frit of 0.5 mm was first made by a sol‐gel method, followed by packing a SPE sorbent in the inlet end of the capillary. Two phenol derivatives, 2,4‐dichlorophenol and 2,4,5‐trichlorophenol, were used as the model compounds. By loading sample solutions into the capillary, the two chlorophenols were extracted into the sorbent. They were desorbed by injecting only about 4 nL of methanol. Finally, the analytes were separated by conventional CE. The technique provided a concentration enhancement factor of over 4000‐fold for both chlorophenols. The detection limits (S/N = 3) of 2,4‐dichlorophenol and 2,4,5‐trichlorophenol were determined to be 0.1 ng/mL and 0.07 ng/mL, respectively. For replicate analyses of 5 ng/mL of 2,4‐dichlorophenol, within‐day and between‐day RSDs of migration time, peak height and peak area were in the range of 1.8–2.0%, 4.0–4.4% and 4.1–4.6%, respectively. The method shows wide linear range, acceptable reproducibility and excellent sensitivity, and it was applied to the analyses of spiked river water samples. The capillary packed with the SPE sorbents can be used for more than 400 runs without performance deterioration.