Determination of Theophylline and Its Metabolites by Liquid Chromatography

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Abstract
A high pressure liquid chromatographic assay has been developed for the separation and quantitatlon of theophylline and its metabolites (1-methyl uric acid, 3-methyl xanthine, and 1,3-dimethyl uric acid), theobromlne, and dyphylllne in biological fluids, viz. human serum, urine, and saliva. The serum has been rendered protein-free by passage through a filter with a nominal molecular weight limit of 10,000. The filtrate is injected onto a reverse-phase column and the separation achieved by utilizing a polar mobile phase and dyphylline (dihydroxypropyl theophylline) as the Internal standard. The results for two normal subjects are included to illustrate the applicability of the technique.