| The dairy products are important nutritional foods, which contain proteins,vitamins and other nutrients, and can provide an essential developmental factor andimmunological components for the aged and infants. However, the dairy productswere polluted due to the abuse of pesticides and veterinary medicines in breeding oflivestock, which can endanger human healths. Some sensitive, simple and reliableanalytical methods were developed to determine the pesticide and veterinary medicineresidues in dairy products. The extraction, separation and concentration of theanalytes in the sample matrices were very important before chromatographic analysis.Liquid-liquid microextraction is a newly developed miniaturized sample pretreatmentmethod, in which the extraction and clean-up can be integrated with concentration.The extraction method has some advantages in respect of extraction efficiency,facility, extraction time and organic solvent consumption. Ionic liquids are a group ofnew “green†organic solvents, which have some unique physical-chemical properties,such as immeasurably low vapor pressure, high thermal stability, moderatedissolvability of organic compounds and structure adjustability. Therefore, ILs areconsidered as replacements for conventional organic solvents and widely applied inchemical fields.In this thesis, ILs were selected as extraction solvents. The liquid phasemicroextraction coupled with high-performance liquid chromatographic detection wasapplied for the determination of pesticide and veterinary medicine residues in dairyproduces.The determination of phenylurea and triazine herbicides in milk based onmicrowave-assisted ionic liquid microextraction （MAILME） coupled withhigh-performance liquid chromatographic separation and detection was described.The experimental parameters of the MAILE, including type and amount of ionic liquid, microwave extraction power, extraction time and salt concentration in sample,were evaluated by a univariate method and orthogonal screening. When60μLof[C6MIM][PF6] was used as extraction solvent the target compounds can be isolatedfrom the4mL of milk. The MAILME is quick （7min） and simple. The detectionlimits for isoproturon, monolinuron, linuron, propazine, prometryne, terbutryn andtrietazine are0.46,0.78,1.00,1.21,1.96,0.84and1.28μg·L1, respectively. Thepresent method was applied to the analysis of milk samples and the recoveries of theanalytes ranged from88.4to115.5%and relative standard deviations were lowerthan8.01%.Ionic liquid-based homogeneous liquid–liquid microextraction （IL-basedHLLME） high-performance liquid chromatography （HPLC） was developed andapplied to the extraction, separation and determination of some antibiotics in milk.The proteins and lipids were removed by adding salt and adjusting the pH value. Thehomogeneous extraction was applied to the improvement of recoveries for IL phaseand analytes. The experimental parameters of the IL-based HLLME, including saltconcentration in sample solution, pH value of sample solution, volume of[C6MIM][BF4], amount of ion-pairing agent （NH4PF6）, and extraction time, wereevaluated. The limits of detection for enoxacin, pefloxacin, norfloxacin, enrofloxacin,sulfamethoxazole and sulfadimethoxine were15.8,7.07,5.13,4.00,7.79and8.33μg·L1, respectively. When the present method was applied to the analysis of milksamples the recoveries of the analytes ranged from92.5to118.6%and relativestandard deviations were lower than6.96%.Ultrasound-assisted ionic liquid/ionic liquid-dispersive liquid-liquidmicroextraction （UA-IL/IL-DLLME） HPLC was developed and applied to theextraction, separation and determination of sulfonamides in infant formula powderedmilk samples. The hydrophobic IL and hydrophilic IL were used as extraction solventand dispersion solvent, respectively. The extraction procedure was induced by theformation of cloudy solution, which was composed of fine drops of [C6MIM][PF6]dispersed entirely into sample solution with help of [C4MIM][BF4]. The purificationof sample and concentration of target analytes were performed simultaneously. Theintroduction of ion-pairing agent （NH4PF6） was beneficial to the improvement ofrecoveries for IL phase and analytes. The experimental parameters of theUA-IL/IL-DLLME, including concentration of [C6MIM][PF6] and [C4MIM][BF4] insample solution, ultrasound extraction time, pH value of sample solution and amount of ion-pairing agent （NH4PF6）, were evaluated. The limits of detection forsulfamerazine, sulfamethizole, sulfachlorpyridazine, sulfamonomethoxine,sulfmethoxazole and sulfisoxazole were2.94,9.26,16.7,5.28,3.35and6.66μg·kg-1,respectively. When the present method was applied to the analysis of infant formulamilk powder samples, the recoveries of the analytes ranged from90.4to114.8%andrelative standard deviations were lower than7.5%. The present method wascompared with IL-based HLLME, ionic liquid-ultrasound-assistedemulsification-microextraction and ionic liquid-temperature-controlled-DLLME. Theresults indicated that the present method is more effective for the extraction of thesulfonamides in milk powder samples.Ionic liquid/anionic surfactant-based aqueous catanionic two-phasemicroextraction （IL/AS-ACTPME） HPLC was developed and applied to theextraction, separation and determination of some antibiotics in milk. The surfactantconcentrations/compositions play an important role in the formation of this system.Meanwhile, the partition behavior of analytes was closely related to the choice ofphase system, pH for separation, and composition of salts. The experimentalparameters of the IL/AS-ACTPME, including concentration of anionic surfactants, thetype and amount of ILs, amount of Na2HPO4·12H2O and （NH4）2SO4, samplesolutionpH value, extraction time and temperature and salt concentration wereinvestigated. The limits of detection for sulfamerazine, sulfamethizole,sulfamonomethoxine and sulfamethoxazole were4.13,3.15,3.50and3.38μg·L-1,respectively. When the present method was applied to the analysis of milk samples,the recoveries of the analytes ranged from93.6to112.9%and relative standarddeviations were lower than6.9%. |
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