Near-infrared spectroscopic method for the sensitive and direct determination of aggregations of surfactants in various media.

A new cmc determination method based on a NIR spectroscopic technique has been developed. Comparing to other cmc determination methods, this NIR method is universal, sensitive, nonintrusive and nonadditive; namely, it can be used for the direct measurements of cmc of normal micelles as well as reversed micelles, without adding any dye or fluorescent probe. cmc values of various surfactants including CTAB, SDS, Triton X-100, Brij-35, Brij-700, Tween-20, SB-12, SB3-10 determined by this method agree very well with those determined by other methods. Additionally, the method can be used for the sensitive and direct determination of cmc values of various nonionic surfactants in room-temperature ionic liquids including [BMIm](+)[PF(6)](-) and [EMIm](+)[Tf(2)N](-). The preliminary results presented here clearly demonstrate that it is possible to use the NIR technique not only to characterize aggregation of surfactants in RTILs but also to determine kinetics and to identify products of reactions in RTILs as well as in microreactors provided by micelles in the RTILs.