| The liquid chromatography for its application related to ionic liquids has been established. The analysis of tri-substituted imidazolium ionic liquids(ILs), the determination of the octanol-water partition coefficients(Kow) and shelf life of tri-substituted imidazolium ionic liquids, the application of ILs for nicotinamide extraction from Thallus laminarie(kelp), by liquid chromatography were carried out. The studies were done by conductivity detector for ion exchange column and ultraviolet(UV) detector for reversed-phase column. This paper describes an accurate, isocratic, reproducible, specific, and sensitive liquid chromatography method, and has its practical application in real life. The study mainly consists of three parts. This study mainly consists of three parts.1. A method was developed for simultaneous determination of four tri-substituted imidazolium ionic liquid cations(1-ethyl-2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-pentyl-2,3-dimethylimidazolium) by ion chromatography using a carboxylic acid cation exchanger bonded to a silica-based column and direct(non-suppressed) conductivity detection. The effects of the type of eluents, organic acid concentration, acetonitrile volume fraction, and column temperature on the cations retention were investigated. The optimal conditions for the method were 2 mmol L-1 methanesulfonic acid + 10 % acetonitrile as an eluent, 1.0 mL min-1 flow rate, and a column temperature of 30 oC. The detection limit(S/N = 3) were 0.82 – 2.39 mg L–1 for the cations. This method was successfully applied to determine tri-subsituted imidazolium ionic liquid cations in spiked tap water. The Kow of these four tri-substituted imidazole substances were also reported in this study.2. The second part of the study describes a rapid and reproducible liquid chromatography method which enables the determination of tri-substituted imidazolium ILs. The chromatographic behavior of four tri-subsituted imidazolium ionic liquid cations(1-ethyl-2,3-dimethylimidazolium, 1-propyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-pentyl-2,3-dimethylimidazolium) has been investigated by reversed phase liquid chromatography(RPLC) using C18 bonded to a silica-based column and ultraviolet(UV) detection. The dependence of the retention properties of these solutes on the types of organic modifiers and its volume fraction, buffer concentration, and column temperature was evaluated. The optimal conditions for the method were 20 mmol/L NaH2PO4/H3PO4 + 20 % methanol as an eluent, 1.0 mL min-1 flow rate, a column temperature of 40 oC, and 220 nm UV wavelength. The detection limits were 0.02 – 0.09 mg L–1 for the cations. The aim of optimizing and improving the selectivity and retention of solute were achieved, method was validated, accurate, and reproducible. It was important to note that ion chromatography(IC) with conductivity detector method for tri-substituted imidazolium ILs determination was reported in the first part of the study. This study emerged as an alternative method using UV detector as it is widely available in laboratory pairing with liquid chromatography. Besides that, this method presented the relatively simple and faster method compared to IC, also this RPLC method was able to baseline separate the compounds while in IC, it was not achieved. The utility of the method has been demonstrated by determining tri-subsituted imidazolium ionic liquid cations spiked into tap water and determining the ILs’ stability. The study of IL’s stability was conducted under four treatments: storage of 4°C; of room temperature; of sunlight; and under the treatment of ultrasound. For a certain period of time until three months, the samples were analyzed by the established LC method to assay and quantify the shelf life of the aqueous-diluted ILs.3. Thallus laminariae(kelp) is widely consumed because of its high concentrations of minerals and vitamins. This study reports the determination of nicotinamide in kelp by liquid chromatography with ultraviolet detection. The nicotinamide was extracted with 0.1N sulfuric acid(pH 0.77) by ultrasound-assisted extraction. The extraction conditions were optimized and a limit of detection of 1.5 μg L-1 and recovery values from 98.05 to 99.51% were obtained. The concentration of nicotinamide was 15.46 ± 0.08 μg/g per dry weight of kelp. Ionic liquids are green solvents and were employed as extractants in this study to reduce the environmental impact. However, the yield of nicotinamide using ionic liquids was lower than using acid extraction. |
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