Electron-capture GC determination of subnanogram amounts of emepronium bromide in serum

Barium peroxide in an acidic medium was utilized to increase the sensitivity in the benzophenone method for the determination of the quaternary ammonium compound emepronium bromide. The method is comprised of ion-pair extraction, oxidation, and quantitative determination of benzophenone by electron-capture GC. By employing small extraction and reaction volumes, the method was used in the 0.2--8-ng/ml range with a relative standard deviation of 2.5% at the 1-ng/ml level. The application of the method to human serum samples after a single oral dose demonstrated that the elimination phase for emepronium in serum had a half-life of 7--11 hr.