Determination of the oximes 2-hydroxyiminomethyl-3-methyl-1-[2-(3-methyl- 3-nitrobutyloxymethyl)]imidazolium chloride and 1-[1-(3-butynyloxymethyl)]-2-hydroxyiminomethyl-3-methylimida zolium chloride in plasma by high-performance liquid chromatography

An assay is presented for the extraction and quantitation of two oximes, 2-hydroxyimino-methyl-3-methyl-1-2-(3-methyl-3-nitrobutyloxyme thyl)] imidazolium chloride (oxime A) and 1-1-(3-butynyloxymethyl)]-2-hydroxyiminomethyl-3-methylimidazo lium chloride (oxime B), in human plasma and is demonstrated to be linear over two overlapping concentration ranges: 10-500 and 100-1000 ng/ml. The assay utilizes a liquid-liquid, ion-pair extraction and a normal-phase chromatographic separation on a silica column with ultraviolet detection at 270 nm. The method is sensitive, rapid and accurate. The limit of detection is 10 ng/ml (signal-to-noise ratio S/N greater than 10). The mean extraction recoveries of the oximes were greater than 86% at all concentration levels. The intra-assay variability was less than 3.3%, the inter-assay variability less than 7.2%. The compound is stable in plasma for 23 weeks when stored at -15 degrees C or -80 degrees C.