Design And Synthesis Of Triazine-based Porous Organic Polymers And Their Application In Solid-phase Microextraction Of Organic Pollutants In Environment And Food

Organic pollutants are easy to migrate,highly toxic and difficult to degrade,which are one of the main causes of environmental and food pollution.Owing to the complex matrix in real samples,the sample pretreatment techniques are necessary to carry out prior to their instrumental detection,which separate and enrich the target analytes as well as reduce or eliminate the possible matrix interference.Solid phase microextraction(SPME)integrates sampling,extraction,enrichment and injection into one step.This technique features with the characteristics of simple operation and environmental-friendliness.Recently,the triazine-based porous organic polymers(TPOPs)-based SPME methods have been applied for enrichment of trace organic pollutants in environment and food samples,which has become one of the research hotspots in the field of sample pretreatment techniques.In this manuscript,a variety of triazine-based porous organic polymers were designed and synthesized,and their analytical properties in the field of SPME were explored.Combined with gas chromatography(GC)or gas chromatography mass spectrometry(GC-MS),the TPOPs-based SPME methods have applied for the analysis of various organic pollutants in food and environment.The main research contents of this paper are as follows:1.A triazine-based covalent organic polymer,CC-TSB,was constructed from the monomers cyanuric chloride(CC)and trans-stilbene(TSB)via the Friedel-Crafts reaction and thereafter used as SPME fiber coating for the extraction of polycyclic aromatic hydrocarbons(PAHs)and their nitrated and oxygenated derivatives.The CC-TSB-based SPME method coupled with gas chromatography/flame ionization detection gives enhancement factors of 548-1236 and limit of detections of 0.40-2.81 ng L-1 for the determination of PAHs and their derivatives.The precision expressed as relative standard deviations(RSDs)for five replicate determinations of the analytes with a single fiber and the fiber-to-fiber RSDs for three parallel prepared fibers were in the range of 4.6-9.4%,and 6.2-10.9%,respectively.The relative recoveries of the analytes for environmental water samples were in the range of 88.6-106.4%with the RSDs ranging from 4.0%to 11.7%(n=5).2.Three covalent triazine-based frameworks(CTFs)were constructed by facile Friedel-Crafts reactions of cyanuric chloride(CC),with triptycene(TPC),fluorene,and 1,3,5-triphenylbenzene,respectively.The CTFs materials were then employed as solid-phase microextraction coatings for the extraction of PAEs.Benefiting from the large surface area and high pore volume,the newly-synthesized CC-TPC-based SPME method exhibited large enrichment factors(978-2157),low limits of detection(0.027-0.084 ng g-1),satisfactory linear ranges(0.09-20 ng g-1),acceptable repeatabilities(4.3-9.6%)and high relative recoveries(92.0-104.6%).Finally,the developed SPME method was demonstrated to be sensitive,reliable,and practical in the analysis of PAEs from food-contacted plastics.3.A covalent organic framework named N-COF was successfully constructed by the aldehyde-amine condensation reaction between 2,4,6-tris(4-formyl phenoxy)-1,3,5-triazine and 1,3-bis(4-aminophenyl)urea for the first time.The prepared N-COF exhibited good stability and high affinity to organochlorine pesticides(OCPs).Thus,the N-COF was served as solid phase microextraction fiber coating for extraction of six OCPs from vegetables and fruits including romaine lettuce,cabbage,Chinese cabbage,apple,pear and peach,followed by quantitation with gas chromatography-electron capture detector(GC-ECD).Under the optimal conditions,good linearities for the OCPs existed in the ranges from 0.1-1.0 ng g-1 to-100.0 ng g-1 for the samples.The low limits of detection for analytes were obtained in the range of 0.03-0.3 ng g-1.The present work can offer new alternative for sensitive analysis of trace level of OCPs in vegetables and fruits.4.Mxene/COF composites were successfully synthesized.By covalently assembling covalent organic frameworks(COF)on MXene nanosheets,the chemical space of MXene lamellar heterostructures was expanded.It not only successfully solves the shortcomings of MXenes materials such as oxidation and collapse,but also retains the excellent properties of porous polymers.Mxene/COF material was successfully made into solid-phase microextraction fiber coating by physical adhesion method.Combined with GC-MS,it was used to determine OCPs in fruit and vegetable samples with satisfactory results.Under the optimum experimental conditions,the SPME method based on MXene/COF has a wide linear range(0.12-20.0 ng g-1),low LODs(0.036-0.090 ng g-1)and good reproducibility(RSDs<9.8%).By comparing the adsorption properties of MXene/COF,COF and MXene,it is proved that MXene/COF composites have a good application prospect in the field of adsorption and separation.