Determination of caffeine by micellar electrokinetic chromatography in different beverages

A fast, simple and cost-effective capillary electrophoresis (CE) method was developed for caffeine determination in different beverages (energy drinks, soft drinks). Because caffeine is neutral from electrophoretic point of view and migrates with the electroosmotic flow (EOF), micellar electrokinetic chromatography (MEKC) was chosen as the separation method. The optimum separation conditions consisted of 25 mM sodium tetraborate, 100 mM sodium dodecyl sulphate, pH 9.30, 20°C temperature, 20 kV voltage, 50 mbar/sec hydrodynamic injection, UV detection at 270 nm. Employing the optimized conditions caffeine was quantified in less than 3 minutes. The analytical performances of the method were verified in terms of accuracy, linearity, limit of detection and quantification, precision and robustness. The method was applied also to detect caffeine in coffee and tea. The advantage of MEKC over other analytical methods, particularly compared with the more frequently used HPLC methods, lies in its lower operating costs and higher environmental friendliness.