Improved quantitation of 2,4-dichlorophenol in plant tissues by high-performance liquid chromatography with amperometric detection

For the determination of 2,4-dichlorophenol (DCP) residues in plant tissues, the use of high-performance liquid chromatography with amperometric detection decreases the quantitation limits by a factor of five compared to those obtained with gas chromatography with Hall conductivity detection. It also avoids the clean-up and derivatization procedures required for electron-capture detection. After extraction of DCP from plant tissue by steam distillation and collection in toluene, an alumina clean-up column is used to remove electroactive interferences from the samples. The DCP is then extracted into aqueous alkaline solution, neutralized, and diluted with acetonitrile to ca. 50% (v/v). An alternative clean-up made use of an in-line, pre-column electrochemical procedure, in which case the alumina column was not used. The components were separated with a reverse-phase column and detected with a polychlorotrifluoroethylene/graphite composite electrode at an applied potential of +1.0 V vs. Ag/AgCl. The quantitation limit for DCP in the plant tissues was 100 pg per injection (0.05 mg Kg^?1).