Preparation Of New Magnetic Nano-Solid-Phase Extraction Agents Fe₃O₄/PAMAM And Their Application In The Detection Of Heavy Metals

With the rapid development of industry,agriculture and transportation,environmental pollution caused by the use and discharge of heavy metal ions has become increasingly prominent,which has seriously affected human living environment and physical health.Therefore,it is of great significance to study the technologies related to the removal and detection of heavy metal ions to control environmental pollution,and improve the quality of human living environment as well as human living standards.Task to detect the content of heavy metal ions accurately has become very important and challenging.Due to the detect limitation of modern analytical instruments,the measurement of trace and ultra-trace elements often has the problems of undetectable and inaccurate measurement.While improving the detection level of modern analytical instruments,the development of sample pretreatment technology is one of the effective ways to improve the detection level.Magnetic-solid-phase extraction is one of the most promising sample pretreatment technologies for its simple operation,short extraction time,low amount of extractant,no column loading,and no clogging during extraction.However,there are not many practical magnetic-solid-phase extraction agents at present,and the main disadvantages of practical magnetic solid-phase extraction agents are low extraction efficiency and poor selective extraction for heavy metal ions.In this thesis,aiming at the trace analysis of heavy metal ions and the shortcomings of traditional magnetic solid-phase extraction technology,we attempted to graft dendrimers with multiful groups onto the surface of magnetic nanomaterials to design and prepare functional core-shell-structure dendrimer magnetic nano-solid-phase extraction agents.A new method for the detection of trace heavy metal ions in the presence of magnetic nano-solid-phase extraction agents coupling with inductively coupled plasma emission spectrometers（ICP-OES）.The main research contents and conclusions are as follows:（1）Using Fe（NO₃）₃·9H₂O and sodium acetate trihydrate as raw materials,Fe₃O₄magnetic nanomaterials with a single grain size of 6-10 nm,higher saturation magnetization（M_s）,lower residual magnetism（M_r）and coercive force（H_c）were prepared by solvothermal method.Fe₃O₄magnetic nanomaterials also show superparamagnetic characteristics,and have achieved a good balance between morphology and magnetic properties,which meets the requirements of Fe₃O₄magnetic nano-solid-phase extraction agents as magnetic cores,the higher M_svalue and lower M_rvalue are beneficial to the recovery of the samples as well as the dispersion in the solution,and the higher specific area is beneficial to the subsequent modification of different functional groups.（2）Using self-made Fe₃O₄magnetic nanomaterials as the magnetic core,and its surface was modified with dopamine.The 2.0 G polyamide-amine（PAMAM）dendrimer was successfully grafted to prepare ammonia-terminated magnetic nano-solid-phase extraction agents,Fe₃O₄/PAMAM-NH₂（referred to as the solid-phase extraction agent FPP-NH₂）,and coupled with ICP-OES for the detection of heavy metal ions Pb²⁺and Cd²⁺.By optimizing the extraction process and elution process,the extraction ability for Pb²⁺and Cd²⁺was improved.The experimental results showed that the solid-phase extraction agent FPP-NH₂can be reused multiple times,and has a higher enrichment factor（100）and a lower method detection limit for heavy metal ions Pb²⁺and Cd²⁺(MDL for heavy metal ions Pb²⁺and Cd²⁺were 0.68and 0.13 ng·m L^-1).The method precision was good(relative standard deviation for metal ions Pb²⁺and Cd²⁺were 1.99%and 2.22%).The spiked recoveries meet relevant standards(the spiked recoveries for heavy metal ions Pb²⁺and Cd²⁺were between 97%-108%).（3）Carboxy-terminated magnetic nano-solid-phase extraction agents（referred to as the solid-phase extraction agent FPP-COOH）were prepared by self-made ammonia-terminated magnetic nano-solid-phase extraction agent（FPP-NH2）as a raw material through carboxylation thereof,and coupled with ICP-OES for the detection of heavy metal ions Pb²⁺and Cd²⁺.By optimizing the extraction process and elution process,the extraction ability for Pb²⁺and Cd²⁺was improved.The experimental results showed that the solid-phase extraction agent FPP-COOH can be reused multiple times,and has a higher theoretical enrichment factor（100）and a lower method detection limit for heavy metal ions Pb²⁺and Cd²⁺(MDL for heavy metal ions Pb²⁺and Cd²⁺were 0.61 and 0.25 ng·m L^-1).The method precision was good(relative standard deviation for metal ions Pb²⁺and Cd²⁺were 2.25%and 2.51%).The spiked recoveries meet relevant standards(the spiked recoveries for heavy metal ions Pb²⁺and Cd²⁺were between 98%-108%).（4）New magnetic nano-solid-phase magnetic extraction agents FPP-NH₂and FPP-COOH were coupled with ICP-OES to detect heavy metal ions Pb²⁺and Cd²⁺.The method has the advantages of high method detection limit,good precision and high recovery rate.