Determination of drugs based on the formation of mixed aggregates with surfactants

Drugs were proved to associate to surfactants constituting true mixed aggregates which behaved similarly to surfactants mixtures. Aggregates studied included anionic-cationic micelles, which showed strong synergistic effects, and dye-induced cationic premicellar aggregates. Threshold concentration values for drugs aggregation were calculated and considered as cmc values. The theory for nonideal mixed micelles, according to which the critical micelle concentration mixed systems depends on the solution composition, could be applied to drug-surfactant mixtures. So, the mixed micelle-based methodology could be extended to the determination of drugs. The analytical applicability of these associations was demonstrated by quantifying phenothiazines at the 10(-7) M level and determining them in pharmaceutical preparations. (C) 1998 Elsevier Science B.V.