Caffeine Research Today is a free monthly online journal that collates and summarizes the latest research about Caffeine, including details on addiction, drugs, effects, coffee.

Determination of caffeine and its metabolites in urine by capillary electrophoresis-mass spectrometry.

Peri-Okonny UL, Wang SX, Stubbs RJ, Guzman NA

Bioanalytical Drug Metabolism, Johnson and Johnson Pharmaceutical Research and Development, Raritan, NJ 08869, USA.

The caffeine content of foods and beverages varies considerably, interfering with our ability to obtain valid interpretations in many human studies with regard to the mechanism of action(s) of caffeine and/or its metabolites. The rate of metabolism of caffeine and other xanthine drugs also varies greatly from one individual to another. Therefore, it is extremely important to develop accurate, reliable analytical methods to quantify caffeine and its metabolites in simple and complex matrixes. A simple method is described for the separation and characterization of caffeine and its major metabolites employing capillary electrophoresis (CE) coupled to ultraviolet-absorption and mass spectrometry (MS) detection. After optimization of the electrophoresis separation conditions, a reliable separation of caffeine and 11 of its major metabolites was achieved in 50 mM ammonium carbonate buffer, pH 11.0. The volatile aqueous electrolyte system used with a normal electroosmotic flow polarity also provided an optimal separation condition for the characterization of the analytes by MS. The CE method achieved baseline resolution for all 12 compounds in less than 30 min. The CE-MS method is suitable for use as a routine procedure for the rapid separation and characterization of caffeine and its metabolites. The usefulness of this method was demonstrated by the extraction, separation, and identification of caffeine and its 11 metabolites from normal urine samples. The urine specimens were first acidified to obtain optimum binding efficiency to the sorbents of the off-line, solid-phase extraction procedure employed here, and an acidified eluent solvent was employed for the desorption step to maximize the recovery of the bound analytes.

Published 11 July 2005 in Electrophoresis, 26(13): 2652-63.
Full-text of this article is available online (may require subscription).

© 2004-2008 Caffeine Research Today. All Rights Reserved.