Development, validation and application of Micellar Electrokinetic Capillary Chromatography method for routine analysis of catechins, quercetin and thymol in natural samples

Natural matrices such as several vegetables, fruits or beverages are the origin of different natural antioxidants with great interest to be used instead of synthetic antioxidants in several applications, as a result of their health-promoting and disease-preventing properties. In this work, a capillary electrophoresis method capable of separating and quantifying some of these antioxidants (seven catechins with the same or similar molecular weight and relation q/z) is showed. Short analysis time and precision parameters equivalent to those obtained by liquid chromatography were obtained. This method was developed using the micellar electrokinetic chromatography (MEKC) mode with ultraviolet-visible detection. Quality parameters were established, obtaining low instrumental detection and quantification limits (0.6-2.0 mg L− 1 and 2.0-6.5 mg L− 1, respectively), good precision (relative standard deviation in the intermediate repeatability lower than 7% for every compound) and short analysis time. The developed method also showed good performance for the determination of two more natural antioxidants, quercetin and thymol. The applicability of the method to the analysis of catechins in several natural samples was tested.