Study Of Extraction Of Triazine And Phenylurea Herbicides In Foods

Herbicides are used widely for weed control, but they can contaminate soil, water,agricultural products, and even animal original foods. It is important for human healthand international trade to monitor herbicides in foods.In this thesis, triazine and phenylurea herbicides were selected as analytes andhigh performance liquid chromatography (HPLC) was applied to separation anddetermination of the analytes. The methods for extracting herbicides in foods werestudied.The ionic liquid foaming-based solvent floatation (ILF-SF) was developed forextracting herbicides from yogurt. Some experimental parameters, including amountof salt, pH value of floatation solution, kind and volume of floatation solvent, kindand volume of ionic liquid, gas flow rate, and floatation time, were optimized. Theanalytes were extracted with acid water solution and then the separation andconcentration of the analytes from the extract were performed by ILF-SF. The mixtureof n-propyl alcohol and ethyl acetate was used as extraction solvent and1-hexyl-3-methylimidazolium hexafluorophosphate was used as foarming agent. Thefloatation time was10min. The detection limits for simeton, simazine, chlortoluron,isoproturon, ametryn, propazine, prometryne, and terbutryn were0.59,0.44,0.44,0.46,0.32,1.01,0.34μg kg-1, respectively, and the enrichment factors for the eightherbicides were11.6,12.9,14.0,16.5,16.2,17.9,18.6and18.5, respectively. In theanalysis of five real yogurt samples, the recoveries of the herbicides varied from86.5to118.7%and relative standard deviations (RSDs) were lower than6.90%.A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was applied to the extraction of triazines and phenylureas from milks and yogurts.Extraction solvent can affect extraction efficicencies of analytes and the co-extractioninterferents. The extraction solvent has a direct impact on clean-up efficicency. Theuseness of proper solvent can effectively reduce the interfenrents and thus improvethe clean-up efficicency. Some experimental parameters, such as extraction solvent,sorbent, pH of sample solution, extraction time, and amount of sodium chloride, wereoptimized. The herbicides were extracted with the mixture of ethyl acetate andn-hexane and the extract was cleaned by primary secondary amine. The frozen-outcentrifugation was applied to further remove fatty. The detection limits for simeton,monuron, chlorotoluron, simetryne, atrazine, karmex, ametryne, and propazine were0.16,0.21,0.18,0.15,0.15,0.35,0.19and0.19μg L-1, respectively. In the analysis ofsix real samples, the absolute recoveries of eight herbicides ranged from80.2to99.8%and RSDs were lower than5.85%.The pneumatic nebulization solid-phase extraction (PN-SPE) was applied to theextraction of triazine herbicides in vegetables. Some experimental parameters,including extraction solvent, pH value of sample solution and PN-SPE solution,extraction time, temperature, type of sorbent, flow rate of carrier gas, pumping rate ofgas, and kind and volume of elution solvent, were optimized. The herbicides wereultrasonically extracted from vegetables with70%methanol. Then the extract wasintroduced to PN-SPE system to further extract. The limits of detection for atraton,desmetryn, atrazine, terbumeton, terbuthylazine, terbutryn, and dipropetryn were0.62,0.59,0.62,0.73,0.98,0.63and1.05μg kg-1, respectively. In the analysis of fourvegetable samples, the recoveries of the herbicides ranged from86.2to110.6%andRSDs were lower than7.51%. Terbutryn, ranging from11.4to18.3μg kg-1, anddipropetryn, ranging from28.7to47.1μg kg-1, were found in real samples.The dispersive solid-phase extraction based on metal-organic framework wasdeveloped and applied to the extraction of triazine and phenylurea herbicides invegetable oils. The separation and determination of herbicides were performed byHPLC. The herbicides were directly extracted with MIL-101from diluted vegetablesoils and no further cleanup was needed. The effects of experimental parameters,including volume ratio of n-hexane to oil sample, mass of MIL-101, extraction time,centrifugation time, eluting solvent and elution time, were investigated. The Student ttest was applied to the evaluation of the selected experimental conditions. The limitsof detection for fenuron, simeton, simazine, atraton, chlortoluron, secbumeton, and terbumeton were1.04,0.72,0.61,0.58,0.97,0.64and0.59μg L-1, respectively. In theanalysis of four vegetable oils, the recoveries of the herbicides ranged from87.3to103.7%.Liquid-phase extraction coupled with metal-organic frameworks-baseddispersive solid phase extraction was developed and applied to the extraction ofherbicides in peanut. The herbicides were separated and determined by HPLC. Theextraction solvent and cleanup procedure are the most important factors for thetreatment of high-fat samples. The experimental parameters, including extractionsolvent, ultrasonication time, volume of hexane, amount of MIL-101(Cr), dispersivesolid phase extraction time, and eluting solvent, were optimized. The herbicides wereultrasonically extracted from peanut using ethyl acetate as extraction solvent. Theseparation of the analytes from a large amount of co-extractive fat was achieved bydispersive solid-phase extraction using MIL-101(Cr) as sorbent. In this step, theanalytes were adsorbed on MIL-101(Cr) and the fat was remained in bulk. The limitsof detection for monuron, atraton, chlortoluron, atrazine, terbumeton, ametryn, andterbuthylazine were1.87,0.99,1.82,1.01,0.98,1.52and1.46μg kg-1, respectively. Inthe analysis of four peanut samples, the recoveries of the herbicides were in the rangeof89.5–102.7%and RSDs were equal to or lower than6.16%.Non-polar solvent dynamic microwave assisted extraction was applied to theextraction of herbicides in soybean. The graphite powders were used as microwaveabsorption medium to heat non-polar solvent which was used for extracting theherbicides in soybeans. In the dispersive solid phase extraction, the herbicides in thehigh-fat extract were directly adsorbed on MIL-101(Cr). The effects of severalexperimental parameters, including extraction solvent, microwave power, flow rate ofextraction solvent, amount of MIL-101(Cr) and dispersive solid phase extraction time,were investigated. The limits of detection for fenuron, monuron, atraton,chlorotoluron, atrazine, ametryn, and terbuthylazine were1.95、1.95、1.71、2.00、1.70、1.56and1.67μg kg-1. In the analysis of four soybean samples, the recoveries ofthe herbicides were in the range of84.9–101.5%...