Studies On Ionic Liquids As Background Electrolyte In Capillary Electrophoresis

Capillary electrophoresis (CE) has been developed from 1980s, which is a kind of separation and determination technique using high dc electric field as driving force and capillary as separation channel. There are several advantages for CE, such as high separation efficiency, short analysis time, low operation cost, high applicability, less consumption of reagent and environment pollution. CE has been widely applied in biology, chemistry, medicine, environmental science, and food safety. Ionic liquids (ILs) are composed of bulky organic cations and small inorganic anions, and are liquid at room temperature. Based on good solubility, conductivity, thermal stability, and negligible vapour pressure, ILs can be used as background electrolyte (BGE), additive, and capillary wall covalent coating reagent in CE. In this thesis, ILs were used as BGE in capillary zone electrophoresis (CZE).In the introduction, the history, sort, property, and synthesis of ILs were introduced, and the application of ILs in CE was summarized.In chapter 2, 1-bulty-3-metylimidazole tetrafluoroborate ([BMIM][BF4]) was used as BGE in CZE for the separation of 11 kinds of amino acids (Ala, Gly, Leu, Lys, Met, Phe, Pro, Ser, Thr. Trp, and Val). The 11 kinds of amino acids was derived by 2,4- dinitrofluorobenzene in the darkness for 60 min first, and then was determined by CZE-UV. The effects of concentration of 1-bulty-3-metylimidazole tetrafluoroborate and pH value of BGE on migration time, electrophoretic mobility, resolution, and separation efficiency, and the effects of applied voltage on migration time of amino acids were studied. The optimal conditions were obtained as follows:60 mmol/L [BMIM] [BF4] (pH 10.00) with the applied voltage of 15 kV. Under these conditions. the 11 kinds of amino acids were completely separated from each other within 16 min. The relative standard deviations (RSDs) of integrated area and migration time were studied, and the RSD values of integrated areas and migration times are<3.O3%and <1.64%, respectively.In chapter 3, a method for the determination of 3 kinds of azo dyes, including Lithol Rubin BCA, OrangeⅡ, and Ponceau SX in lipsticks by CZE using ILs as BGE was established. Because the lipsticks are ropy and ceraceous, it is difficult to weight the sample and to extract azo dyes from bulky lipstick samples. A new method was introduced to surmount this difficulty. The lipsticks were coated on the surface of glass slide, and then the glass slide was put into the extraction vessel for extraction. The amount of sample on the surface was about 0.01g, and 25ml of methanol was used as extraction solvent. The ultrasonic extraction was performed for 30 min, and then the sample solution was injected into CE system. The effects of concentration of ILs, pH value of BGE, and applied voltage on separation of 3 kinds of azo dyes were studied. The optimal conditions were obtained as follows:60 mmol/L [BMIM][BF4] (pH 12.50) with the applied voltage of 15 kV. Under these conditions, the 3 kinds of azo dyes were completely separated from each other within 12 min. The method was applied for the analysis of two kinds of lipsticks. Lithol Rubin BCA, which can be used in mouth cosmetics, was found in the lipsticks, and the content were 55.05 mg/g and 30.50 mg/g, respectively. OrangeⅡand Ponceau SX, which are forbidden to mouth cosmetics, were not found in the two kinds of lipsticks. The recoveries from 99.8% to 108.8% were obtained.In chapter 4, a method for the determination of 4 kinds of fluoroquinolones (FQs), including sparfloxacin, pefloxacin, fleroxacin and pazufloxacin in blood samples by CZE using ILs as BGE was established. The method was based on matrix solid-phase dispersion (MSPD) extraction, using diatomite as dispersant. The effects of ratio of sample to diatomite, types of elution solvents, and elution solvent volume were studied. When the ratio of sample to diatomite was 1:3. and 10 mL acetonitrile-0.2 mol/L NaOH aqueous solution (v/v,9:1) was used as elution solvent, the extraction fields of 4 kinds of FQs were satisfactory. The eluate was evaporated to dryness,and the residue was dissolved in 0.5 mL 10 mmol/L NaOH. The resulting sample solution was filtered with a membrane, and then injected into the CE system. The effects of concentration of ILs and pH value of BGE on separation of 4 kinds of FQs were studied. The optimal conditions were obtained as follows:100 mmol/L [BMIM][BF4] (pH 11.0) with the applied voltage of 15 kV. Under these conditions, the 4 kinds of FQs were completely separated from each other within 11 min. The recoveries from 45.4% to 86.4% were obtained for 4 compounds in pig blood and deer blood at fortification levels (3μg/mL and 10μg/mL) with RSD<9.45%. The proposed method was rapid, simple, and can make the extraction and purification be performed in one step. Both of the sensitivity and selectivity of the method were satisfactory.In chapter 5, a method for the determination of 4 kinds of sulfonamides (SAs), including sulfaquinoxaline, sulfadimethoxin, sulfadimidin, and sulfamethoxazole in meat by CZE using ILs as BGE was established. The method was based on MSPD, and the effects of types of dispersants, ratio of sample to dispersant, washing solvent volume, types of elution solvents, and elution solvent volume were studied. When Al2O3 was used as the dispersant, the ratio of sample to Al2O3 was 1:1,9 mL of n-hexane was used as washing solvent, and 9 mL of ethylacetate was used as elution solvent, the extraction fields of 4 kinds of SAs were satisfactory. The eluate was evaporated to dryness, and the residue was dissolved in 0.5 mL 10 mmol/L NaOH. The resulting sample solution was filtered with a membrane, and then injected into the CE system. The effects of concentration of ILs and pH value of BGE on separation of 4 kinds of FQs were studied. The optimal conditions were obtained as follows:80 mmol/L [BMIM][BF4] (pH 11.5) with the applied voltage of 15 kV. Under these conditions, the 4 kinds of SAs were completely separated from each other within 12 min. The recoveries from 37.31% to 116.77% were obtained for 4 compounds in pork, beef, and chichen at fortification levels (2.5μg/g and 10μg/g) with RSD<12.66%. The proposed method was simple, rapid,and less consumption of samples. It is unnecessary to make centrifugation, protein precipitation and re-extractions, and the extraction and purification can be performed in one step.