Non-ionic micellar affinity capillary electrophoresis for analysis of interactions between micelles and drugs

Micellar affinity capillary electrophoresis (MACE) was introduced to evaluate the affinity of various kinds of drugs as benzoic acid, salicylic acid, trinitrophenol, p-hydroxybenzoic acid and o-acetylsalicylic acid. Non-ionic micelles as Brij 35 (polyethylenglycol dodecylether), Tagat (polyoxyethylene (20) glycerol monooleate) and Tween 20 (polyoxyethylen sorbitan monolaurate) were used as a pseudostationary phase in capillary electrophoresis. For polyvinyl alcohol (PVA) coated capillary was used in this examinations. The drugs had negative electrophoretic mobilities at a pH value of pH 7.2. The negatively charged drugs migrated toward the anode and were related by their interaction with the micelles. The difference in the mobility of the drugs owing to the presence of the micelles reflected the interaction between these drugs and the micelles. Equations were derived to calculate the capacity factor k' from the migration times in the presence of micelles t' and in the absence of micelles t, the partition coefficients Pwm and the Gibbs free energy. The drugs show different interaction and affinity with the micelles in the systems. Strong interaction was observed between benzoic acid and the micelles. Furthermore, a linear relationship (R = 0.999) was obtained between deltaG(o) and ln Pwm in the micellar solubilization of drugs. These results show that deltaG(o) can give us information on the affinity and on the partition behaviour of the drugs in these systems.