Chromatographic separation of 3,4-difluorophenylacetic acid and its positional isomers using five different techniques.

The separation of five positional isomers from 3,4-difluorophenylacetic acid was investigated using normal- and reversed-phase high-performance liquid chromatography, capillary zone electrophoresis, gas chromatography and supercritical fluid chromatography. Operating parameters of each technique, such as temperature, type of stationary phase, mobile phase pH, ionic strength, organic modifiers and additives were varied in order to elucidate the separation mechanisms. Based on the advantages and disadvantages of each methodology, a simple and practical RPLC method was selected. The method was validated in terms of linearity, limit of detection, accuracy, recovery, ruggedness and precision.