title: Simple high-performance liquid chromatography method for the simultaneous determination of serum caffeine and paraxanthine following rapid sample preparation.
abstract: A simple reversed-phase high-performance liquid chromatography (HPLC) method for the simultaneous determination of caffeine and paraxanthine in human serum is described. Serum proteins are precipitated with perchloric acid and the resulting supernatant neutralized for direct injection onto an HPLC column. The method uses a phosphate-methanol mobile phase (85:15, v/v) at pH 4.9 with a flow-rate of 1.75 ml/min and quantitation is by UV absorbance at 274 nm. Elution times are approximately 18 min for caffeine and 8 min for paraxanthine. Theobromine and theophylline have elution times of 5.4 and 9.4 min and do not interfere in the assay. The intra-assay and between-assay means for precision and accuracy for both drugs are: 4.5% C.V. and 3.3% deviation. The sensitivity of the method is 50 ng/ml for each drug.
authors.affiliation: Department of Pediatrics, University of California, San Diego, La Jolla 92093, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Holland
authors.forename: K A
authors.initials: KA
authors.lastname: Godfredsen
authors.forename: T
authors.initials: T
authors.lastname: Page
authors.forename: J D
authors.initials: JD
authors.lastname: Connor
mesh_terms: D002110:Caffeine / Q000097:blood*; D000697:Central Nervous System Stimulants / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007202:Indicators and Reagents; D010472:Perchlorates; D011786:Quality Control; D015203:Reproducibility of Results; D013056:Spectrophotometry, Ultraviolet; D013806:Theophylline / Q000097:blood*
chemical_list: D000697:Central Nervous System Stimulants; D007202:Indicators and Reagents; D010472:Perchlorates; D002110:Caffeine; D013806:Theophylline; C021183:1,7-dimethylxanthine