Study And Application Of Metal-organic Nanotubes Combined With Dispersive Solid-phase Extraction For Detection Of Persistent Organic Pollutants In Water

POPs（persistent organic pollutants）,refers to the organic contaminants of natural or artificially synthetic which can migrate for long a distance with the help of environmental media（water,air,organisms,etc.）and can be persistent in the environment and human body.They can cause serious damages on the environment and human health.POPs persist in the environment for a long time and do harm to human beings through food chain amplification.Therefore,the development of sensitive rapid and low cost methods to determine a variety of POPs is of great importance for human health and environmental protection.In this study,we synthesize a novel adsorbent material:the lead（II）-based metal organic nanotubes,and based on this adsorbent,we developed a dispersive solid-phase extraction method coupled with GC-MS/MS and GC-NCI-MS to determinate PCBs and PBDEs in the environmental water samples.The applicability of this method was tested.Besides,its adsorption capacity for malachite green in water was discussed.The research details and results are as follows:Firstly,porous lead lead（II）-based metal organic nanotubes were synthesized by a biphasic solvothermal method usingβ-cyclodextrin,PbCl₂ and triethylamine as materials,cyclohexanol as framework.The translucent nanotubes were obtained after heated at certain temperature and pressure for three days.Scanning electron microscopy,Fourier transform infrared spectroscopy and X-ray diffraction were adopted to characterize the nanotubes.Then we developed a d-SPE method with Pb-MONTs as absorbent,coupled with GC-NCI-MS for the detection of seven PBDEs from environmental water samples.The extraction conditions（amount of adsorbent,ionic strength,extraction time and pH）were optimized through response methodology,while the desorption conditions（the type and volume of desorption solvent）were optimized separately.The method validation and the analysis of real samples were conducted under the optimal conditions.Besides,the comparison was conducted between the developed method and traditional methods.Results showed that the novel adsorbent had great robustness and chemical stability,and it has great adsorption capacity towards trace PBDEs in water samples.The recoveries ranged from 80.5%to 119.2%,which demonstrated the superiority compared with other reported methods.Second,the novel adsorbent was synthesized under a optimized conditions and used for detection of polychlorinated biphenyls in water samples.A new d-SPE-GC-MS/MS method was developed to determinate trace PCBs.We took single factor optimization method to optimize the desorption conditions（type of desorption solvent）,and response methodology was used to optimized adsorption condition（amount of adsorbent,extraction time and iron strength）in order to get the optimal experimental conditions.The methodology validation and the analysis of real samples were conducted under the optimal conditions.Meanwhile,we took the new MONTs compared with existing materials and discussed the possible adsorption mechanism.The experimental results showed that the Pb-MONTs have a good performance for detection of trace PCBs in drinking water.Results showed that the d-SPE-GC-NCI-MS method achieved low LODs(0.26-0.82 ng L^-1),wide linear range(5-1000 ng L^-1)and good repeatability（RSD<5.5%）.Finally,several kinds of organic pollutants were selected as target compounds,including PBDEs,chlorobenzenes and HBCDs,to investigate the possible extraction mechanism of Pb-MONTs.Results showed that compounds with delocalizedπsystem can be easily adsorbed as the existence of cation-πbonds.Static adsorption for malachite green was conducted and it shows that Pb-MONTs have great adsorption efficiency and the saturated adsorption for malachite green is 476.2 mg/g.Experiments show that second-order reaction kinetics and the Langmuir isothermal model are more suitable for isothermal adsorption.