MOFs Membrane Solid Phase Extraction-UPLC-MS-MS Used In The Detection Of Pesticides And Ultraviolet Absorbers In Environmental Water

Metal Organic Frameworks（MOFs）are a kind of nanoporous materials that formed by metals or metal clusters and organic ligands.Dueto their large specific surface area,high porosity,tunable pore size,and easyfor modification,MOFsshow excellent adsorption performance,and have good application prospects in sample pretreatment and adsorption of water pollutants.In practical applications,to improve the selectivity of MOFs and overcome the complex separation procedure of MOFs due to their powdery crystal form,new MOFs materials such as various modified MOFs materials,MOFs composite materials and MOFs derivative materials are gradually being developed and utilized.Phenoxycarboxylic acid herbicides are widely used because of their low cost and good weeding efficiency.However,they are highly water-soluble and difficult to be degraded in aquatic environments.They will remain for a long time and exhibit potential threats to aquatic organisms and human health.Benzotriazole ultraviolet absorbers are widely used in daily necessities and industrial products.they can effectively absorb ultraviolet rays and reduce the damage caused by ultraviolet rays.However,they have low degradability and bioaccumulation,and have been detected in various environmental water bodies and organisms.Because their concentrations in environmental water bodies are very low,the sample pretreatment process is necessary for the enrichment of analytes before the instrument analysis.In this paper,two MOFs materials were synthesized,and then functionalized and high-temperature carbonized,respectively.finally,were embedded into a mixed matrix membrane.These materials were used as adsorbents in sample pretreatment for phenoxycarboxylic acid herbicides and benzotriazole ultraviolet,combined with ultra-high performance liquid chromatography tandem mass spectrometry detection,the main contents are as follows:（1）The metal organic framework material MIL-101-NH₂was synthesized by hydrothermal method,mixed with polyvinylidene fluoride to prepare the MIL-101-NH₂-PVDF mixedmatrix membrane,and then the mixed matrix membrane was functionalized by quaternary amine using methyl trifluoromethane to prepare a cationic MOF mixed matrix membrane（MIL-101-NMe₃⁺-PVDF MMM）,and the prepared membrane materials were characterized.These membraneswere used as adsorbentsfor mambrane extraction of seven phenoxycarboxylic acid herbicides in water.The conditions that affect the extraction efficiency were optimized.The method for the determination of seven phenoxycarboxylic acid herbicides in environmental water samples by MIL-101-NMe₃⁺-PVDF MMM membrane extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry（UPLC-MS/MS）was developed.The linear range of 2,4-D,MCPA,2,4,5-T,2,4,5-TP and 4-CPA in this method was 1-500 ng/L,and the linearity of 2,4-DB and PB he range was 5-500 ng/L.The limit of detection of this method for 7 analyteswere 0.10-0.90 ng/L,and the intra-day precision（n=5）and inter-day precision（n=5）were 1.4%-9.4%and4.2%-12.6%,respectively.This method was applied to the detection of phenoxycarboxylic acid herbicides in tap water and surface water.The recoveries of tap water samples were 75%-102%;the recoveries of surface water samples were72%-126%.The method has advantages such as,simple operation,low limit of detection,and good accuracy,which could meet the analysis requirements.（2）UiO-66-NH₂was synthesized by solvothermal method and carbonized at800℃to obtain nanoporous carbon material（NPC）,then NPC was embedded into NPC-PVDF mixed matrix membrane and have been characterized.The membraneswere used as adsorbents for the enrichment of benzotriazole ultraviolet absorbers in water,and some conditions that affect the extraction efficiencies including the amount of MOF,extraction time,pH,salinity,eluent type,eluent volume,elution time were optimized.In combination with ultra-high performance liquid chromatography-tandem mass spectrometry detection,a method for the analysis and detection of four benzotriazole ultraviolet absorbers in environmental water samples has been established.The linear range of the established method was 5-1000ng/L,and the limits of detection of the method in ultrapure water,seawater and sewage are 0.23-1.12 ng/L,0.25-1.12 ng/L and 0.32-1.40 ng/L,respectively.The intra-day precision（n=5）and the inter-day precision（n=5）were 3.0%-12.2%and4.9%-13.3%,respectively.The method was applied to the detection of benzotriazole ultraviolet absorbers in seawater and domestic sewage.The recoveries of seawater samples were 64.2%-92.7%,and the recoveries of sewage samples were71.9%-102.8%.