HIGH-PERFORMANCE LIQUID CHROMATOGRAPHIC DETERMINATION OF THEOPHYLLINE IN HUMAN SERUM

A simple, rapid and sensitive HPLC method for the determination of theophylline (T) in human serum has been developed. An isocratic system consisting of a /-l Bondapak C18 column, mobile phase of methanol, phosphate buffer (22:78, pH=4.5), and a flow rate of 1.4 mL/min was used. The eluent was detected by UV at 275 nm at room temperature. 8-Chlorotheophylline (8-CT) was used as an internal standard. The serum samples deproteinated by methanol containing 8-CT and the supernatant was injected into the HPLC system. The retention times of 5.7 and 8.1 min were found for T and 8-CT, respectively. The linearity was checked in the range of 0.2- 30 µg/mL. Relative standard deviation for both inter-day and intra-day precision analysis was less than 5%. No interference was observed from endogenous serum components. Specificity was shown against some commonly co-administered drugs. Simple and fast sample preparation, small sample volume (250 µL), precision, reproducibility, specificity, sensitivity and high percentage recovery (98 %) make the method to be practically useful for T monitoring in asthmatic patients.