title: New simplified microassay for the quantitation of theophylline and its major metabolites in serum by high-performance liquid chromatography.
abstract: A high-performance liquid chromatographic technique is presented for simultaneous determination of theophylline, 3-methylxanthine, 1-methyluric acid, 1,3-dimethyluric acid and caffeine in serum using beta-hydroxyethyltheophylline (BHET) as an internal standard. An aliquot of a serum sample (100 microliters) was added to 40 microliters of an internal standard solution (BHET; 100 micrograms/ml) and vortexed. A 20% trichloroacetic acid solution (60 microliters) was then added; the mixture was vortexed, centrifuged and 100 microliters were injected onto a C8 column maintained at 45 degrees C. Inter- and intra-day variability of the assay for all compounds was less than 4.3%. Sensitivity ranged from 10 ng/ml for 1-methyluric acid to 25 ng/ml for theophylline. Drugs commonly coadministered with theophylline did not interfere with the assay.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D011786:Quality Control; D013806:Theophylline / Q000097:blood*; D013997:Time Factors
chemical_list: D013806:Theophylline