Concentration of hydrophobic organic compounds and extraction of protein using alkylammoniosulfate zwitterionic surfactant mediated phase separations (cloud point extractions)

Abstract

The zwitterionic surfactants 3-[nonyl- (or decyl-) dimethyl-ammonio]propyl sulfate, (C9-APSO4 or C10-APSO4) were synthesized using Nilsson's procedure, and their phase separation behavior under different experimental conditions was evaluated. The results indicate that such zwitterionic surfactants can be utilized for the extraction/preconcentration of hydro-phobic species in a manner akin to that previously reported for nonionic surfactants. This was demonstrated for several practical applications including the extraction/preconcentration of some steroidal hormones and vitamin E prior to high-performance liquid chromatography analysis. The zwitterionic surfactant mediated phase separation was also applied to the extraction of the hydrophobic membrane protein, bacterio-rhodopsin, from the hydrophilic cytochrome c protein, both originally present in an aqueous phase. The concentration factors for this aqueous two-phase extraction technique using C10-APSO4 ranged from 26 to 35 with recoveries in the range 88 to greater than 96%. Some comparative studies indicate that the use of zwitterionic surfactants in lieu of nonionic surfactants (e.g. polyoxyethylene(7.5) nonyl phenyl ether PONPE-7.5) in such an extraction method offers some significant advantages such as purer, homogeneous surfactant preparation, minimum background absorbance at UV detection wavelengths, the two-phase region occurring at lower temperatures, and greater extraction efficiencies/concentration factors among others.