The Application Of Deep Eutectic Solvent In The Separation And Photochemical Sensing Of Complex Samples

Due to characteristics of simple synthesis,low toxicity and eco-friendlily,deep eutectic solvent（DES）is known as the new"green solvent"in the new century and has been widely used in the field of separation analysis.DES is mainly composed of hydrogen bond donor and hydrogen bond acceptor in a certain molar ratio.Therefore,functional DESs can be designed and synthesized according to the physical and chemical properties of the analyte,the difference in detection technology and separation method.Designing a new DES containing multiple functional groups to modify nano-magnetic particles and combining magnetic solid-phase extraction（MSPE）technology to separate target analytes in complex samples.It has the advantages of simple operation and high adsorption efficiency.DES with surfactant like properties can be used to build a new aqueous micellar two-phase system（AMTPS）with aqueous two-phase system（ATPS）extraction technology.Moreover,as a fluorescence sensitizer,DES can be applied to establish a new fluorescence sensing detection system with metal nanoclusters.At the same time,enzyme like nanomaterials modified with DES can be devoted to construct enzyme colorimetric probes for colorimetric sensing and detection.In this study,a series of new types of DESs with various functions and special properties were designed and synthesized.Combined with MSPE,ATPE,fluorescence and colorimetric sensing technology,several new systems and methods for the separation and analysis of target analytes in complex samples were constructed.The main research contents are as follows:（1）Magnetic solid-phase extraction for the removal of mercury from water with ternary hydrosulphonyl based deep eutectic solvent modified magnetic graphene oxideA ternary hydrosulphonyl based DES（THS-DES）was prepared and decorated on magnetic graphene oxide to synthesize the magnetic adsorbents（THS-DES@M-GO）.Combined with MSPE,the THS-DES@M-GO was used for the removal of mercury(Hg²⁺)from water.Under the optimal adsorption conditions,the R%of THS-DES@M-GO to Hg²⁺could achieve 99.91%.Methodological investigations showed that the method established in this research had excellent precision,repeatability and stability.Thermodynamic experimental studies revealed that the adsorption mode of Hg²⁺by THS-DES@M-GO fitted well with the Langmuir model,and the maximum adsorption capacity was 215.1 mg·g^-1.Reuse research showed that 94.94%of Hg²⁺could be eluted from the adsorbent.And after 7 repeated,THS-DES@M-GO still maintained a high removal rate of 90.23%for Hg²⁺.The MSPE technology established in this research could be used to remove actual mercury-containing wastewater.（2）Ternary multiple functional groups based deep eutectic solvent modified magnetic Mn Fe₂O₄-multiwalled carbon nanotubes for solid-phase adsorption of trypsinA ternary multiple functional groups DES（TMFG-DES）was prepared and decorated on magnetic multiwalled carbon nanotubes to prepare a multifunctional magnetic composite nano-materials（Mn Fe₂O₄-MWCNTs@DES₁）.Combined with MSPE,Mn Fe₂O₄-MWCNTs@DES₁ were utilized to the adsorb trypsin（Try）.The response surface methodology（RSM）experiments were prepared under Box-Behnken Design,which were applied to optimize the adsorption conditions for Try.RSM result showed that the practical maximum adsorption capacity for Try was 1020.1 mg·g^-1.The kinetics and adsorption isotherms results showed that the second-order kinetic model and Langmuir isotherm model were perfectly matched with the adsorption process.Mechanism exploration proved that electrostatic interaction,hydrogen bonding interaction and chelation interaction were the dominant force for Mn Fe₂O₄-MWCNTs@DES₁ to high-performance adsorption of Try.The activity of Try after elution had been analyzed,and the result illustrated that the enzyme activity,conformation and secondary structure of Try did not change significantly.The proposed method had effective practical applicability to isolation Try from crude bovine pancreas.As a result,the proposed method provided a potential value in the adsorption of biomacromolecule.（3）Aqueous micellar two-phase system composed by deep eutectic solvents for extraction of pigmentsTwo types of DESs with surfactant-like properties were synthesized:DL/PEG400and[N₈₈₈₁]Cl/PEG400.Combined with the ATPS technology,a novel AMTPS based on a hydrophilic/hydrophobic DESs was designed（DES/DES-AMTPS）.Three typical pigments were selected as target analytes to evaluate the application of the DES/DES-AMTPS.Through single factor and RSM,the extraction conditions were systematically optimized.Under the optimal conditions,it was found that almost 95.00%sunset yellow and 99.75%sudan（III）distributed in the micellar-rich phase,whereas nearly all of methylene blue stayed in the micellar-poor phase.Mechanism study proved that the formation of micelles between pigments and DESs by hydrophobic and electrostatic interaction were the dominant force in the separation.In addition,this research not only realized the transfer of the pigments between the two phases,but also recovered and reused of[N₈₈₈₁]Cl/PEG400 in the regeneration studies.（4）Fluorescence determination of iron with copper nanoclusters based on fluorescence enhancement effect of deep eutectic solventA kind of copper nanoclusters（Aci-Cu NCs）based on tartaric acid as protective agent was synthesized.It was found that the surfactant-like DES could form micellar co-aggregation with Aci-Cu NCs,resulting in an increase in fluorescence intensive of Aci-Cu NCs.The fluorescence sensing assay（Aci-Cu NCs@DES）based on DES sensitization was applied for the determination of Fe³⁺.Under the optimum conditions,the assay worked in the Fe³⁺concentration ranges from 1-20μM and had a detection limit（LOD）of 0.0374μM.Selective experiments and practical application research results showed that the Aci-Cu NCs@DES system had specific recognition of Fe³⁺in real water samples.The fluorescence assays offer a new idea for the establishment of a novel fluorescence detection system.（5）A composite prepared from Mn O₂ nanosheets and deep eutectic solvent as an oxidase mimic for the colorimetric determination of DNAA new type of nanomaterial（DES/Mn O₂）with oxidase-like activity was fabricated by modifying the DES on Mn O₂ nanosheets.Owing to the oxidase-like activity of DES/Mn O₂,it could oxidize the colorless 3,3’,5,5’-tetramethylbenzidine（TMB）into a blue product（ox TMB）with an absorption spectrum at 652 nm.DNA was easily adsorbed on the surface of the DES/Mn O₂ by hydrogen bonding and electrostatic interactions,which leading to the oxidation activity of DES/Mn O₂ on TMB was inhibited.Based on the above mechanism,a colorimetric sensing assay for the determination of DNA by DES/Mn O₂-TMB system was established.Under the optimum conditions,the DES/Mn O₂-TMB system could quantitatively detect DNA in a concentration range of 10-100μg·m L^-1 with a LOD of 0.37μg·m L^-1.The selectivity study showed the DES/Mn O₂-TMB system to be highly selective for DNA.The real sample analysis result illustrated that the proposed method could be used for the detection of DNA in bovine whole blood.The DES/Mn O₂-TMB system established in this study holds promising potential applications in sensing and biotechnology.