Utilization of solid-phase microextraction–high-performance liquid chromatography in the determination of aromatic analyte partitioning to imidazolium-based ionic liquid micelles

A solid-phase microextraction (SPME)–high-performance liquid chromatography (HPLC) approach is used, for the first time, to study the partitioning behavior of eight aromatic analytes to three imidazolium-based ionic liquid micelles, namely, 1-hexadecyl-3-methylimidazolium bromide (HDMIm-Br), 1-hexadecyl-3-butylimidazolium bromide (HDBIm-Br), and 1,3-didodecylimidazolium bromide (DDDDIm-Br). The model used to calculate the partition coefficients is improved by determining the accurate critical micelle concentration (CMC) value of the studied IL-micelles, which considers the nature and amount of organic modifier used in the experiments. Proper CMC values in the model improve the quality of the results and decrease the differences between theoretical and experimental intercepts. Surface tensiometry has been utilized to determine the CMC values for the micelles at different acetonitrile contents (1% and 1.5%, v/v). The calculated partition coefficient values for polycyclic aromatic hydrocarbons (PAHs) oscillate between 631 and 5980, whereas aromatic analytes with a lower number of fused rings in their structures suffer non-partitioning to any of the IL-micelles. The obtained partition coefficients to IL-micelles were highest with the DDDDIm-Br IL and were always higher than those obtained with the traditional surfactant cetyltrimethyl ammonium bromide (CTAB).