Liquid chromatographic analysis of dichlorophen and its major impurity

A rapid and simple high-performance liquid chromatographic (HPLC) method for the analysis of dichlorophen in raw material and in dichlorophen-toluene soft gelatin capsules for veterinary use was developed using a reverse-phase technique. This HPLC system was shown to isolate dichlorophen from its major impurity (the trimer). Three formulations were assayed and were found to contain 7.14, 7.90, and 8.4% of the trimer. A C-18 column was used with a mobile phase of methanol-water (75:25). The flow rate was 1.5 mL/min, and the effluent was monitored at 290 nm for both dichlorophen and the trimer. Dichlorophen and the trimer had retention times of 6.5 and 9.0 min, respectively.