High Performance Liquid Chromatographic Assay for Alpha-Difluoromethylornithine in Rodent Feed

A high performance liquid chromatographic method has been developed for the assay of alpha-difluoromethylornithine, an inhibitor of cell growth, in rodent feed at levels from 0.5 to 50 mg/ml. The drug is leached from the feed with water, and a portion of the aqueous solution is passed through a cation exchange resin to remove some feed components which are simultaneously leached. The drug is removed from the resin column and derivatized with 1-fluoro-2,4-dinitrobenzene to enhance its ultraviolet absorptivity. The derivative is isolated from the reaction mixture and chromatographed on a 25-cm LiChrosorb RP-18 column equipped with a guard column, using a mobile phase of pH 4.8 acetate buffer:tetrahydrofuran (80:20) and photometric detection at 360 nm. The method is also applicable for the assay of feed preparations of other amino acids or similar non-UV absorbing materials which react with 1-fluro-2,4-dinitrobenzene to give dinitrophenyl derivatives.