Novel determination of caffeine in human urine by direct analysis in real time mass spectrometry

Determination of caffeine is necessary for clinical research. A new method for the determination of caffeine in human urine was established by direct analysis in real time mass spectrometry using multiple reaction monitoring. The m/z 195.1 to 138.1 amu transition was employed in positive ionization mode. The preparation and analysis conditions were systemically optimized. The calibration curve was linear from 0.5–50 µg/mL with a limit of detection limit of 0.2 µg/mL. Intra-day and inter-day accuracy and precision were within the acceptable limits of ±15% at all concentrations. Moreover, the matrix effects for the determination of caffeine were evaluated. In conclusion, a simple, rapid, and reliable method without complex sample preparation and chromatographic separation was developed and validated for the determination of caffeine in human urine.