(ENANTIO-)SEPARATION OF PHENOXY ACID HERBICIDES USING CAPILLARY ZONE ELECTROPHORESIS

Capillary zone electrophoretic (CZE) methods were developed for the separation of phenoxy acid herbicides and related impurities (including positional isomers) originating from production processes. In addition, chiral separations of phenoxy-propionic acid herbicides were achieved by adding a suitable cyclodextrin-type chiral selector to the electrophoresis 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 electropherograms obtained with CZE systems having different selectivities. The CZE method shows good precision, linearity and long-term stability. The methods developed have been successfully applied to the analysis of real production samples and the determination of their enantiopurity. Both the identification and determination of the impurities compare with the results obtained with chromatographic methods. The CZE methods, however, are more flexible and simpler and will be more economical. The methods have potential for automated quality control assays.