Nonaqueous Capillary Electrophoresis of Chlorinated Phenols

The contents of pentachlorophenol (PCP) and 2,3,5,6-tetrachlorophenol (TeCP) in textile products are regulated for safety. Since an organic solvent such as 2-methoxyethanol is needed to extract chlorinated phenols from textile samples, nonaqueous capillary electrophoresis has been applied to achieve the separation of PCP and isomers of TeCP. The run buffer was 100 mM Tris/acetate in methanol whose pH was adjusted to 8.0. All of the analytes were negatively charged at pH 8.0 and their electrophoretic velocities were higher than the electroosmotic flow of the methanol buffer. A reverse voltage of -20 kV was applied along a 27-cm fused silica capillary with ID of 50 μm, and PCP and 3 TeCP isomers were separated based on the difference in $pK_a$ values in less than 4 min. The limits of detection (S/N = 3) were about 0.02 μM. By varying pH of the methanol run buffer, $pK_a$ values of the 4 chlorinated phenols were also estimated.