Application Of New Adsorbents In The Detection Of Some Organic Pollutant Residues In Environmental And Food Samples

Instrumental analysis is the main analytical method for detecting contaminants in food and environmental samples today.However,because there are complex matrix effects in these samples and the content of contaminants are at low concentration levels,it is difficult to directly detect.Therefore,it is necessary to perform pretreatment process on the samples before analysis.In recent years,several pre-treatment methods have been developed.Solid phase extraction(SPE)and magnetic solid phase extraction(MSPE)have gradually become the preferred method of sample pretreatment due to the advantages of high enrichment factor and low solvent consumption.In this work,two graphene composite materials and one covalent organic framework materials were prepared by consulting and researching literature,and used as adsorbents for solid phase extraction and magnetic solid phase extraction.Combined with high performance liquid chromatography(HPLC)-ultraviolet detection(UV),methods for detecting phenylurea herbicides and carbamate pesticides in water samples,vegetable samples,and beverage samples were established.1.Graphene oxide was covalently modified with p-phenylenediamine via a diazonium reaction.The resulting material was employed as a sorbent for the solid-phase extraction of six phenylurea herbicides(metoxuron,monuron,chlortoluron,isoproturon,monolinuron,and buturon)from environmental water and lettuce leafs.Some key factors that influence the extraction efficiency were studied,including sample loading rate,sample pH,and desorption conditions.Following desorption with acetonitrile,the analytes were quantified by HPLC with UV detection.Under optimal extraction conditions,for water sample,the linear range of the six phenylurea herbicides was 2.0-100 ng mL-1 with the correlation coefficient of 0.9990-0.9998,and LODs(S/N=3)was 0.1-0.25 ng mL-1.For lettuce samples,the linear range was 5-100 ng g-1 with the correlation coefficient being 0.9915-0.9986,and the LODs was 1.5-2.5 ng g-1.These results show that the sorbent has a large potential for the enrichment of organic pollutants.2.Graphene-carbon nanosphere composite(G@CNS)was prepared via a simple hydrothermal method.The G@CNS nanocomposite was characterized by X-ray diffraction,scanning electron microscope,surface area and porosity analysis.The G@CNS was applied as a new sorbent for solid-phase extraction of five carbamate pesticides(tsumacide,carbaryl,isoprocarb,bassa,diethofencarb)prior to quantitative determination by high-performance liquid chromatography with ultraviolet detection at 208 nm.Some experimental parameters including desorption conditions,sample pH,sample volume,and loading rate were studied carefully.Under the optimized condition,the method provided good linearity ranging from 0.3 to 100.0 ng mL-1 with low limits of detection of 0.10-0.20 ng mL-1 for grape juice,0.10-0.30 ng mL-1 for blend fruit juice,and 0.10-0.20 ng mL-1 for water sample.Good method recoveries(80.2-110%)with relative standard deviations less than 7.2%and high enrichment factors(167-293)were achieved.Results demonstrated that this novel G@CNS can serve as a promising alternative sorbent for more applications.3.In this work,a core-shell structured magnetic covalent organic framework named as M-TpDAB was constructed with 3,3'-diaminobenzidine(DAB)and 1,3,5-triformyl-phloroglucinol(Tp)as building units.M-TpDAB was characterized by nitrogen adsorption-desorption isotherms,powder X-ray diffraction,scanning electron microscopy and transmission electron microscopy.Using the M-TpDAB as adsorbent,a simple and highly effective method was proposed for preconcentrating phenylurea herbicides before high performance liquid-phase chromatography analysis.In the optimized conditions,a good linearity was achieved within the range of 0.15-100 ng mL-1 for water sample,1.0-100.0 ng mL-1 for tea drink samples.The limits of detection for the analytes were 0.05-0.15 ng mL-1 for water sample and 0.30-0.50 ng mL-1 for drink samples.Satisfactory recoveries of spiked target compounds were in the range of 84.6%-105%for water sample and 80.3%-102%for tea drink samples.Finally,the M-TpDAB based method was successfully used to determine phenylurea herbicides in tea drinks and water samples,demonstrating a good alternative for analyzing trace level of phenylurea herbicides in water samples.