Determination of enviroxime in a variety of biological matrixes by liquid chromatography with electrochemical detection.

A simple and specific method has been developed for determination of enviroxime in biological samples. Enviroxime, a substituted benzimidazole, its coisomer zinviroxime, and the internal standard hexestrol were extracted from the samples with benzene. The benzene layer was evaporated and the residue was reconstituted and injected onto a liquid chromatograph. Reversed-phase chromatography on an octylsilane column with a 65% methanol-35% 0.14 M sodium acetate mobile phase separated the components. The compounds were detected electrochemically using a glassy carbon electrode held at +0.85 V. The assay could detect as little as 4 ng of enviroxime/ml of plasma, 15 ng/ml of nasal wash, and 20 ng/ml of urine or tissue homogenate. For plasma assays, the procedure was greater than 97% accurate and had a relative standard deviation of less than 4%. This method has proven to be applicable and reliable for the determination of enviroxime in many types of biological samples. Several problems encountered during the routine use of electrochemical detection were explored and minimized.