In addition, hydrogen bonding, dipole-dipole, and dispersive interactions can contribute to the solute partitioning between the two phases [4][5][6].CE was originally considered as a powerful analytical tool for the analysis of biological macromolecules. It has though, over the years, been extensively used for the separation of other compounds, such as chiral drugs, food additives, pesticides, inorganic ions, organic acids, and others. In this chapter, the ability of CE, and particularly CZE and MEKC, to be used for the qualitative and quantitative determination of compounds in pharmaceutical, biological and natural samples is investigated. In each approach, a number of studies are reported and discussed. These studies involve establishment of optimum separation conditions, method validation, optimization of sample-preparation procedure and application for the determination of the analytes under study in real samples. The first part of this chapter involves the determination of polyphenolic compounds using CZE with UVVis detector in red and white wines, while the second part involves the determination of pharmaceutical compounds in biological samples, such as blood and urine, using the hyphenated technique CE-MS (mass spectrometry). The third and final part emphasizes the importance of MEKC in chiral analysis since it has been known that usually only one enantiomer is active, while the other may be less active, inactive or has adverse effects.
Determination of polyphenolic compounds in natural samplesPolyphenolic compounds exist in a variety of natural products, such as fruits, vegetables, beverages (tea, wine and juices), honey, cacao and herbs. They attract a lot of interest due to their beneficial implication in human health. They have been widely studied due to their antioxidant capacity and their association with several pathological conditions, such as hypertension, cardiovascular disease, dementia, and even cancer [7][8][9]. Therefore, due to their health significance, numerous analytical methods have, over the last decades, been developed for their separation, identification and quantitation in natural products [10][11][12][13].According to literature, the simplest CE method, CZE, proved to be the best method for the determination of polyphenolic compounds in wine samples [14][15][16][17]. In such studies, and in each case, when the optimum CZE method was applied to different red and white wines, it was established that red wines have higher levels of polyphenolic compounds than white wines and that the polyphenolic composition varies among different wines.