Analysis of chlorophenoxy acid herbicides by cyclodextrin-modified capillary electrophoresis

In this study, we developed a capillary electrophoresis method involving cyclodextrins to separate seven chlorophenoxy acid herbicides and their enantiomers. The cavity size and the concentration of cyclodextrins heavily influenced the migration time of individual herbicides. The peak resolution also varied with different concentration ratios of cyclodextrins. Adding 4 mM alpha-cyclodextrin and 1 mM beta-cyclodextrin in the buffer was found to produce the optimum experimental condition. The herbicides examined in this study could be successfully separated within 7 min; meanwhile, the two pairs of enantiomers could also be completely resolved. The calibration lines' correlation coefficients for the separation conditions were all above 0.996. The dynamic range of the analysis of seven herbicides was at least two orders, from 1 ppm to 100 ppm. Analyzing the seven herbicides by capillary electrophoresis posed the advantages of a high resolution, high separation efficiency and good reproducibility. By combining with a C-18 disk preconcentration method, the herbicides' detection limits in the environmental water were below 1 ppb.