Rapid quantitative liquid chromatographic determination of caffeine levels in plasma after oral dosing.

A simple method is described for the rapid, quantitative analysis of caffeine in human plasma. Caffeine levels present in plasma following drug administration were determined by high-performance liquid chromatography with UV detection at 273 nm after plasma protein precipitation. Caffeine was detectable at levels as low as 0.1 micrograms/mL. Mean recoveries of 98% with a coefficient of variation of 3% were obtained for plasma standards, in which concentrations ranged from 0.1 to 8 micrograms/mL. Interassay variability of the slope of the standard curve had a coefficient of variation of 3%. Application of this method during human bioavailability studies is described.