A coacervative extraction based on single-chain and double-chain cationic surfactants.

A coacervative extraction (CAE) with the common cationic surfactants dodecyltrimethylammonium bromide (DTAB) and didodecyldimethylammonium bromide (DDAB) was firstly developed. Notable characteristics of the CAE was the use of low concentration of salt (0.1molL-1 NaBr) at ambient temperature and without the requirement of organic solvent. The CAE was based on phase separation due to the neutralization of the surface charge of the micelle by electrostatic interaction with the predominant common counter ion (bromide). The coacervative phase was subjected to an optimized micellar liquid chromatography with UV (MLC-UV) method without any treatments. The method was applied to the determination of penicillins including amoxicillin, ampicillin, penicillin-G, oxacillin, and cloxacillin in milk samples. Method detection limits (MDLs) from standard were 0.5-2ngmL-1, and 40-80-fold analyte enrichment were obtained. The CAE-MLC-UV has shown to be of high potential for the analysis of five penicillins in milk with recoveries >90%.