High Performance Liquid Chromatographie Procedure for the Simultaneous Determination

Summary: A sensitive HPLC method is reported for the Simultaneous determination of theophylline, caffeine, and phenobarbital in 100 of plasma. After a single extraction of the drugs with chloroform/isopropanol (90 4-10 by volume) at low pH in the presence of an excess of ammonium sulphate they are resolved and quantified using a reversed-phase column (Spherisorb 5 ODS). The drugs are eluted with a binary-solvent gradient System (acetonitrile/phosphate buffer pH 4.6) at room temperature and monitored at 204 nm. Quantitation is based on peak-height ratio of analyte tp interval Standard (8-chlorotheophylline). Complete Chromatographie resolution of all drugs is achieved within 15 min. The method is linear to 40 mg/1 \ of theophylline and caffeine, and to 80 mg/1 of phenobarbital. Numerous drugs and xanthine metabolites P tested do not interfere.