Metal-Organic Frameworks Based Dispersive Solid Phase Extraction Of Benzo[a]pyrene And Tetracyclines In Food Samples

The development of new food analytical methods is of great significance for food safety and quality control.At present,highly sensitive food analytical techniques require complex pre-treatment of food samples to reduce interference from complex matrices and lower detection limits.The diversity of food samples and analytical targets also puts forward higher demands on pretreatment techniques.In this paper,dispersive solid phase extraction(d-SPE)was selected as a solution for food sample pretreatment.Metal-organic frameworks(MOFs)with various structures and excellent adsorption properties were used as extractants to establish d-SPE with strategy of “a single MOFs material for a single target,compounded MOFs materials for a variety of targets”.And we explored the adsorption and extraction properties in different solvents,designed and optimized extraction steps such as solvent types and dosage.Followed with high performance liquid chromatography(HPLC)tandem fluorescence detector(FLD)and triple quadrupole mass spectrometry(MS/MS),the methods provided promising application for the pretreatment and determination of edible oil and honey samples.This paper mainly includes the following two parts:(1)MIL-101(Cr)was selected as the extractant because of the pore size consistency,and d-SPE and matrix solid phase dispersion(MSPD)were established for determination of the benzo[a]pyrene(BaP)in edible oil.MIL-101(Cr),MIL-100(Fe)and MIL-53(Al)were synthesized by hydrothermal methods.X-ray diffraction,scanning electron microscopy and BET test were accomplished for characterization of the molecular structure,crystal shape size and specific surface area.HPLC-FLD with the optimal parameters of chromatography and detector was established for BaP determination.The dispersibility and stability of MIL-101(Cr)in solvents such as n-hexane,ethyl acetate,acetone and dichloromethane were investigated.N-hexane and acetone were selected as diluent and eluent,respectively.The amount of extractants and solvents were optimized to establish d-SPE.The linear range of d-SPE-HPLC-FLD method was 1-30 ng/mL,the detection limits(LOD,S/N=3)and limit of quantification(LOQ,S/N=10)were 0.19 ng/mL and 0.56 ng/mL,respectively.The recoveries of practical samples spiked in 3 levels were between 79.6%-117.1%,and the relative standard deviation(RSD)was less than 9.6%.On this basis,MSPD was established by using empty solid phase extraction columns packed after dispersive adsorption.The linear range of MSPD-HPLC-FLD method was 1-50 ng/g,LOD and LOQ were 0.33 ng/g and 1.09 ng/g,respectively.The recoveries were 96.0%-99.9%,and the RSD was 1.2%-9.2%.Both methods have been successfully applied to the determination of practical samples,and they both meet requirement of the limit in national standards.The methods realized the direct extraction with MOFs in oily and fatty food samples and expanded the application in hydrophobic organic solvents.(2)The d-SPE method with compounded MOFs as extractant was established,and the content of four tetracycline(TCs)antibiotics in honey was determined by HPLC-MS/MS.A high performance liquid chromatography tandem triple quadrupole mass spectrometry(HPLC-MS/MS)method was established with the optimized parameters The difference of adsorption and extraction of 4 TCs antibiotics by MOFs and the difference of structure and adsorption properties of 3 MOFs were investigated.The MOFs were compounded in mass ratio 1:1:1,3:1:1,7:1:2,and they were compared by examining the amount of residual TCs after adsorption and recovered TCs.The optimal compounding ratio was 7:1:2,and it was proved that the comprehensive adsorption-extraction ability was better than using a single MOFs.The extraction steps,types and amount of extractants and eluents were designed and optimized.The established d-SPE was used for the pretreatment of the honey samples and the determination of the TCs residues.The d-SPE-HPLC-MS/MS method has LOD of 0.073-0.435 ng/g for four TCs,LOQ of 0.239-1.449 ng/g,and an upper detection limit of 500 ng/g.The method was successfully applied to TCs determination in 5 honey samples with matrix matching method.The recoveries of the 3 spiking levels were between 88.1%-126.2%,which achieved high matrix matching the accuracy.The method realized the improvement of adsorption extraction effect and increased recoveries of multiple targets by compounding extractants.The method provided a strategy for measurement of multi-target enrichment by d-SPE and were also of practical value in honey samples.