New polar-embedded stationary phase for surfactant analysis.
The separation and identification of surfactants is a challenge due to the diversity of surfactants, the complex composition of surfactant raw materials, and the complexity of the sample matrices. High-performance liquid chromatography (HPLC) is the preferred analytical technique, because it allows the characterization of surfactant raw materials according to their composition and the quantitation of individual surfactants in complex mixtures. Although many HPLC columns are available for surfactant analysis, none of these columns provide optimal selectivity for the simultaneous analysis of anionic, non-ionic, and cationic surfactants using the same mobile phase system. In this paper, we describe a new polar-embedded stationary phase for the simultaneous analysis of anionic, non-ionic, and cationic surfactants with a simple and volatile mobile phase system containing ammonium acetate buffer and acetonitrile, utilizing evaporative light-scattering detection (ELSD). Mobile phase ionic strength and pH are important for optimizing chromatographic conditions. The column offers ideal selectivity for different types of surfactants, excellent peak shapes, especially for cationic surfactants, improved resolution for oligomers in ethoxylated surfactants, and compatibility with highly aqueous mobile phases. Thus, it can be used not only for quality assurance of individual surfactants, but also for the analysis of a variety of surfactant-containing formulations.