Evaluation of quail egg white riboflavin binding protein as a chiral selector in capillary electrophoresis by applying a modified partial filling technique

A preliminary evaluation of the enantioselective properties of quail egg yo lk riboflavin binding protein (qRfBP) was carried out in capillary electrop horesis by using the complete filling technique. The most promising results obtained by this screening of nineteen chiral drugs were singled out with the aim of optimizing enantiomer separations by applying the partial fillin g technique, which allows operating at much higher protein concentrations w ithout detection problems. The building of the separation zone in the parti al filling technique has been modified in order to enable on-line monitorin g, before each run, of the actual protein plug application velocity and, co nsequently, the building of a plug of the desired length. The electrophoret ic conditions chosen gave opposite migration directions for the chiral sele ctor and the analytes, with qRfBP migrating away from the detector. A polyv inyl alcohol-coated capillary was first totally filled with protein and the optimal plug length was obtained by further applying negative pressure tog ether with positive voltage for the time needed. Separations of basic drugs were optimized by using protein concentrations ranging from 200 mu M up to 900 mu M and different plug lengths, while the running buffer pH (6.0), te mperature (25 degrees C) and operating voltage (+20 kV) were kept constant. The enantioresolution of all solutes was affected by both the chiral selec tor concentration and protein plug length. Baseline separations were obtain ed for oxprenolol, prilocaine and bupivacaine.