Capillary zone electrophoretic (CZE) methods were developed for the se
paration of phenoxy acid herbicides and related impurities (including
positional isomers) originating from production processes. In addition
, chiral separations of phenoxy-propionic acid herbicides were achieve
d by adding a suitable cyclodextrin-type chiral selector to the electr
ophoresis buffer. The selectivity of the separation can be controlled
and fine-tuned by using different types of cyclodextrins. The presence
of specific impurities could be confirmed after comparison of the ele
ctropherograms obtained with CZE systems having different selectivitie
s. The CZE method shows good precision, linearity and long-term stabil
ity. The methods developed have been successfully applied to the analy
sis of real production samples and the determination of their enantiop
urity. Both the identification and determination of the impurities com
pare with the results obtained with chromatographic methods. The CZE m
ethods, however, are more flexible and simpler and will be more econom
ical. The methods have potential for automated quality control assays.