Once a good resolution between all charged vitamins was obtained, the aim of the study was to obtain a separation of the two uncharged vitamins, B3 (nicotinamide) and B12. MEKC has been used to accomplish the separation of both neutral and ionic analytes. The presence of micelles of surfactants in the BGE acts as a “pseudostationary phase”, which leads to both hydrophobic and electrostatic interactions with solutes. For this purpose, three different surfactants (SDS, SC and SDC), at different concentration levels (25e75 mM range), were tested. These surfactant systems were selected due to the type and properties of micelles that each one forms. Thus, SDS forms spherical micelles with a hydrophobic inner core and a charged shell, while bile salts (SC and SDC) provide helical micelles with reverse orientation than SDS . When the three surfactants were tested, the best results in terms of separation performance were obtained using 40 mM SDS (Fig. 3A), 50 mM SDC (Fig. 3B) and 50 mM SC (Fig. 3C). From this study, it is interesting to observe that in the SDS system the vitamin B1 migrated very slow (Fig. 3A), whereas short migration times were achieved for bile salts (see Fig. 3B and C). This behaviour can be explained by the electrostatic (ion paring) interaction between the positive charge of thiamine observed that only SDS was able to resolve B5-C vitamin pair. Thus, this surfactant was selected for the following studies.