Analysis of dicamba degradation by Pseudomonas maltophilia using high-performance capillary electrophoresis

A method based on high-performance capillary electrophoresis (HPCE) was developed for the simultaneous analysis of dicamba and its metabolites in media containing the bacterium Pseudomonas maltophilia. Dicamba, 3,6-dichlorosalicylic acid (DCSA), and related products were extracted from media samples using ether under acidic conditions and injected onto an HPCE system containing a pH 10.0 running buffer. Baseline resolution between these compounds was obtained at 30 kV with a total run time of 6 min on a 50-microns i.d. x 50-cm capillary. The linear range for dicamba and DCSA detected at 274 nm extended from 0 to 100 mg/liter and the dynamic range for both compounds extended to 2000 mg/liter. The within-run precision was +/- 5% or less throughout the entire concentration range studied. The limits of detection for dicamba and DCSA in the media samples were 6 and 2 mg/liter. This corresponded to detection limits of 0.3 and 0.1 ng, respectively, in the injected extracts. With this method it was possible to conduct preliminary studies examining the kinetics of dicamba metabolism in P. maltophilia.