title: High performance liquid chromatographic procedure for the simultaneous determination of theophylline, caffeine, and phenobarbital in neonates.
abstract: A sensitive HPLC method is reported for the simultaneous determination of theophylline, caffeine, and phenobarbital in 100 microliters of plasma. After a single extraction of the drugs with chloroform/isopropanol (90 + 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 to interval standard (8-chlorotheophylline). Complete chromatographic resolution of all drugs is achieved within 15 min. The method is linear to 40 mg/l of theophylline and caffeine, and to 80 mg/l of phenobarbital. Numerous drugs and xanthine metabolites tested do not interfere.
mesh_terms: D002110:Caffeine / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007231:Infant, Newborn; D010634:Phenobarbital / Q000097:blood*; D013056:Spectrophotometry, Ultraviolet; D013806:Theophylline / Q000097:blood*
chemical_list: D002110:Caffeine; D013806:Theophylline; D010634:Phenobarbital