Microextraction by packed molecularly imprinted polymer to selectively determine caffeine in soft and energy drinks

The method reported herein show the development of a microextraction by packed sorbent (MEPS) coupled to high performance liquid chromatography - ultraviolet detection method for the selective determination of caffeine (CAF) in soft and energy drinks. It was synthetized a molecularly imprinted polymer (MIP) as adsorbent material, which was properly characterized showing high stability and good adsorption capacity. Theoretical findings showed that four hydrogen bonds established between CAF and methacrylic acid (monomer) play a major role on the spontaneity and stability of the analyte-monomer (1: 4 stoichiometry) pre-polymerization complex. After optimization, the best MEPs conditions were: 4 mg of MIP, 150 mu L of sample at pH 4, 200 mu L of methanol: acetic acid (9: 1, v/v) as elution solvent and one draw-eject cycle reaching CAF recovery around 100%. The developed method was properly validated and presented, linearity in the range from 1.0 to 50.0 mu g mL(-1), in addition to satisfactory selectivity, precision and accuracy. Finally, the method has been successfully applied to samples of energy and soft drinks.