SIMULTANEOUS DETERMINATION OF THEOPHYLLINE AND CAFFEINE BY REVERSED PHASE LIQUID-CHROMATOGRAPHY USING PHENYL COLUMN

Phenyl, C-8, and C-18 columns were evaluated for the simultaneous analysis of theophylline (TH) and caffeine (CA). The phenyl column was chosen for its capability of resolving of 1,7-dimethylxanthine from theophylline. The procedure utilized protein precipitation of either 50 or 100 mu l of serum with diluted trichloroacetic acid, followed by analysis with either a manual isocratic or automated gradient elution mode. Chromatographic conditions were: column equals phenyl (4. 5 multiplied by 150 mm with a 4. 5 multiplied by 50 mm guard column), mobile phase equals phosphate or acetate/ACN, and detection wavelength equals 280 nm.