title: Simultaneous determination of caffeine and its primary demethylated metabolites in human plasma by high-performance liquid chromatography.
abstract: An improved high-performance liquid chromatographic method for the simultaneous determination of caffeine and its three primary metabolites (theophylline, theobromine and paraxanthine) in human plasma is described. The four substances were separated on a reversed-phase column (5 microns TSK gel ODS-80TM, 150 mm x 4.6 mm I.D.) by use of the mobile phase methanol-0.1 M NaH2PO4 (30:70, v/v) with a flow-rate of 0.8 ml/min. Absorbance was monitored at 274 nm. The detection limit was 5 ng/ml for theobromine and caffeine and 10 ng/ml for paraxanthine and theophylline. The linearity and reproducibility were sufficient for drug monitoring of caffeine and its primary methylxanthines.
authors.affiliation: Institute of Community Medicine, University of Tsukuba, Ibaraki-ken, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Tanaka
mesh_terms: D000328:Adult; D002110:Caffeine / Q000097:blood*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013805:Theobromine / Q000097:blood*; D013806:Theophylline / Q000097:blood*
chemical_list: D002110:Caffeine; D013806:Theophylline; D013805:Theobromine; C021183:1,7-dimethylxanthine