Application Of Ionic Liquid-based Aqueous Two-phase System To The Extraction Of The Pesticides And Veterinary Medicines From Tea Drinks And Milk

In recent years, with the rapid development of economy and thecontinuous improvement of living standards, food safety problems causedwidespread concern. The chemical contaimination in food causing by theinappropriate use of pesticides and veterinary medicines during theprocess of the agricultural and animal husbandry production can damagehuman health. It is important to develop the rapid, effective methods todetermine the target or non target organic chemicals in food. Becausethere are variety of pesticides and veterinary medicines, the samplematrix is also complex, and the low concentrations of pesticides andveterinary medicines commonly found in food samples, the developing rapid,effective, high sensitivity method is of great importance for the reliabledetermination the residues of pesticides and veterinary medicines.Aqueous two-phase system(ATPS) is a novel liquid liquid extraction method.Ionic liquid (IL) based aqueous two-phase system has the advantages ofboth ATPS and IL, such as low-toxicity, little emulsion, low viscosity,simple, short time in phase separation and high enrichment factor. Inrecent years, IL-based ATPSs were widely used in sample pretreatment. Inthis thesis IL-based ATPS was applied to the extraction of the pesticidesand veterinary medicines from tea drinks and milk.IL-based ATPS was applied to the extraction of six sulfonamides (SAs) from milk samples.1-Butyl-3-methylimidazolium tetrafluoroborate andsodium citrate were used to form ATPS. To achieve optimum extractionperformance, several experimental parameters, including the type and theamount of salt, the type and amount of IL, ultrasonic time and pH of samplesolution, were investigated and optimized. Under the optimal experimentalconditions, good linearity was observed in the range of8.55-1036.36ng·mL-1with the correlation coefficients (r) ranging from0.9995to0.9999. The limits of detection and quantification were in the range of2.04-2.84and6.73-9.37ng·mL-1, respectively. The present method wassuccessfully applied to the determination of SAs in milk samples, and therecoveries of analytes were in the range of72.32-108.96%with relativestandard deviations ranging from0.56to12.20%. The results shows thatthe present method is rapid, feasible and environmentally friendly andthe method is suitable for the determination of SAs in milk samples.IL-based ATPS was established and applied to the extraction of fourpyrethroid insecticides from tea drinks prior to the determination byhigh-performance liquid chromatography.1-Butyl-3-methylimidazoliumtetrafluoroborate and ammonium sulphate ((NH4)2SO4) were used to form ATPS.At the same time, ultrasound-assisted extraction was adopted to shortenthe extraction equilibrium time and improve the mass transfer rate. Themain parameters affecting the extraction efficiency, including type andthe amount of ionic liquid, type of salt, ultrasonic time, pH value ofsample solution, type of reverse extraction solvent, concentration of(NH4)2SO4and volume of cyclohexane, were investigated. Under the optimalexperimental conditions, good linearity was obtained (r＞0.998). Therecoveries of pyrethroids obtained by analyzing the four spiked teasamples were from70.22to122.10%. The intra-day and inter-day precisionwere in the range of2.65-11.00%and1.95-10.83%(n=5), respectively.Limits of detection for determining the analytes were in the range of4.86- 9.53ng·mL-1. The results showed that the present method providesacceptable recoveries and precision for the determination of pyrethroidinsecticides in the tea samples and suitable for determination ofpyrethroid insecticides in complex matrices.