| Along with the development of science and technology and the continuousimprovement of living standards, the food safety problem and the environmentalpollution problem have drawn extensive public concern. Recently, food safetyincidents kept intruding and the environmental pollution problem became more andmore serious, which pose a direct, indirect or potential threat to the security of theecological environment and human health. Therefore, there is an urgent need toestablish a simple, reliable, and highly sensitive method for monitoring the tracelevels of pollutants in environmental and food samples. Owing to the complexity ofsample matrices and low levels of analytes, the analyte enrichment and samplecleanup are of vital importance prior to chromatographic analysis.Liquid-phase microextraction is a novel sample pretreatment method, which hassome advantages such as simplicity, nearly solvent-free consumption and highenrichment factor. Ionic liquids (ILs) are considered as potential environmentallyfriendly extraction solvents due to their unique physicochemical properties, such asgood solubility for various organic compounds and metal ions, good thermal andchemical stability, and structure adjustability. Recently, ILs has a wide application insample preparation.In this thesis, two kinds of new sample preparation methods were developed, inwhich solid-state IL was used as extraction solvent. The liquid-liquid microextractionwas applied for the extraction of sulfonamides in environmental waters and Sudandyes in red wines followed by detection using high-performance liquidchromatographic.The determination of four sulfonamides in environmental water samples basedon microwave-assisted dispersive liquid-liquid microextraction coupled with high-performance liquid chromatographic detection was described. In this newtechnique, we used solid-state IL as extraction solvent. The solid-state extractionsolvent1-ethy-3-methylimidazolium hexafluorophosphate ([C2MIM][PF6]) can bemelted into liquid phase and then completely dispersed into the aqueous solution withthe help of microwave irradiation. The large contact surface between the sample andextraction droplets speeds up mass transfer so that the extraction time decreased andthe extraction efficiency improved. Several experimental parameters, includingamount of extraction solvent, microwave power and irradiation time, pH of samplesolution, and ionic strength, were evaluated. The limits of detection for sulfathiazole,sulfachlorpyridazine, sulfamethoxazole, and sulfaphenazole were0.39,0.33,0.62, and0.85μg/L, respectively. When the present method was applied to the analysis ofenvironmental water samples, the recoveries of the analytes ranged from75.1to115.8%and relative standard deviations were in the range of1.1-11.9%.A novel microwave-assisted homogeneous ionic liquid microextraction(MA-HILME) method was developed for the extraction of Sudan dyes in red winesfollowed by detection using high-performance liquid chromatography.1-Dodecyl-3-methylimidazolium bromide ([C12MIM]Br) was used as extractant in amicrowave-assisted extraction procedure, and then transferred into hydrophobicsolid-state IL after adding ammonium hexafluorophosphate ([NH4][PF6]). Theexperimental parameters of MA-HILME, including type and amount of extractionsolvent, microwave power and irradiation time, amount of ion-exchange reagent([NH4][PF6]), pH of sample solution, and ionic strength, were evaluated. The limits ofdetection for Sudan I, Sudan II, Sudan III, and Sudan IV were0.19,0.18,0.24, and0.16μg/L, respectively. When the present method was applied to the determination ofSudan dyes in red wines, satisfactory recoveries were obtained in the range of78.5-106.8%, and relative standard deviations were ranged from1.1to9.7%. |
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