Ionic Liquids in Sample Preparation Techniques and an Examination of their Micellization Behaviors

Ionic liquids (ILs) are a class of non-molecular ionic solvents. Their unique properties including wide viscosity ranges, nearly no measurable vapor pressure under room temperature, high thermal stability, and a multitude of varying solvation interactions, make them an ideal class of substituent of traditional organic solvents in various sample preparation techniques. The first part of this dissertation includes an introduction of ionic liquids and their applications in sample preparation techniques. The following chapters in this part introduce various sample preparation techniques using ionic liquids as extraction solvents. Tris(pentafluoroethyl)trifluorophosphate (FAP)-based ILs have been applied for the first time as extraction solvents for direct immersion single drop microextraction studies. The high hydrophobicity and hydrolytical stability of the FAP-based ILs permit them to be used in the sampling of large volumes of aqueous solutions without dissolution or loss of the ILs. Micellar ILs (micelles formed in IL with the iv addition of different surfactants) are used as extraction solvents to perform the extraction of 17 aromatic compounds from aqueous solution with a headspace single drop microextraction method. A novel IL-based dispersive liquid-liquid microextraction method has been introduced, which utilizes an in situ metathesis reaction to form an IL phase for the preconcentration of aromatic compounds from water. In addition, the IL-based dispersive liquid-liquid microextraction is also applied to extract 14 emerging contaminants from water. The selectivity and sensitivity of the method can be controlled by utilizing FAP-based IL with various functional groups.;Surfactant-like ILs show a self-aggregation behavior in aqueous solutions and have been a focus of recent investigations. The second part of this dissertation begins with an introduction of the surfactant and miclles, the micellization behavior of ILs, as well as two convenient methods to determine analyte-micelle partition coefficients. A chapter is then presented describing a method using micellar solid phase micrextraction combined with high performance liquid chromatography to determine the partition coefficients between eight aromatic analytes to three imidazolium-based IL micelles. The final chapter introduces the surface and micellar properties of two imidazolium-based ILs in aqueous solutions with the presence of several organic solvents. In addition, a preliminary study of the utilization of IL micelles as mobile phases in micellar liquid chromatography was presented.