A rapid and simultaneous analysis of theophylline and its metabolites in human whole blood by ultra-performance liquid chromatography-tandem mass spectrometry

A rapid and sensitive method for analysis of theophylline and its six metabolites in human whole blood by ultra-performance liquid chromatography (UPLC)–tandem mass spectrometry (MS/MS) using 3-isobutyl-1-methylxanthine as internal standard is presented. After pretreatment of a blood sample by liquid–liquid extraction with acetonitrile, theophylline and its metabolites were analyzed by UPLC with a Poroshell 120 EC-C18 column and Acquity TQD tandem quadrupole mass spectrometer equipped with an electrospray ionization interface. The calibration curves for theophylline and its metabolites spiked into human blood showed equally good linearities in the microgram per milliliter range. The detection limits (signal-to-noise ratio 3) were as low as 0.1–1.0 ng/ml. The method gave satisfactory recovery rates, accuracy, and precision for quality control samples spiked with theophylline and its metabolites. To further validate the present method, 100 mg of theophylline was orally administered to a healthy male volunteer and the concentrations of theophylline and its metabolites in blood were measured 0.5, 1, 2, 4, and 8 h after dosing. The concentrations of theophylline in human blood were between 0.82 and 2.38 μg/ml. The present method should be very useful in forensic and clinical toxicology and pharmacokinetic studies.