Investigation of the interactions between drugs and mixed bile salt lecithin micelles - A characterization by micellar affinity capillary electrophoresis (MACE) .3.

Mixed micelles, which mimic the bile in the gastrointestinal tract, were used as a pseudostationary phase in capillary electrophoresis. The mixed micellar system studied contained sodium glycodeoxycholate (NaGDC) or sodium taurocholate (NaTC) as bile salt and lecithin (LC) or dipalmitoylphosphatidylcholine (DPPC) as phospholipid. The determination of the changing mobilities of ionic analytes in the presence of mixed micelles reflected interactions between the used drugs and the mixed micelles. These were estimated according to the lipid concentration in the bile salt (BS)/phosphatidylcholine (PC) micelles and the capacity factors k for the partition were calculated whenever possible. For the calculation of k it is important to characterize the formation of the mixed micellar phase and to estimate the ionic mobility of the mixed micelles. In doing so two different methods were applied in order to determine this micellar phase. The partition equilibrium of basic and acidic drugs depends considerably on size and shape of the micelles as well as on the lipophilicity of the drug. This paper also outlines the use of electrospray mass spectrometry and MS-MS for the characterization of mixed micelle composition. (C) 1997 Elsevier Science B.V.