Novel Extraction Techniques Based On Deep Eutectic Solvents And Their Application In Environment Analysis

Heavy metal pollution has become one of the most serious environmental pollution problems today.Excessive heavy metal elements in the environment not only cause great harm to human beings but also affect the virtuous cycle of the ecosystem.Therefore,it is very important to implement effective testing for various environmental samples.As a key step in the sample analysis process,the sample preparation technology is responsible for the enrichment and separation of the analyte from the complex original matrix into the solvent,which determines the reliability of the final analysis results.After decades of development,the sample preparation technology has become increasingly simple and convenient from the early time-consuming and labor-intensive work,and the analytical performance has also been greatly improved.However,these innovations were carried out at the methodological level,and cannot completely solve the problem of pollution in the analysis method itself.Deep eutectic solvents(DESs)were considered as a new type of green solvents that can replace traditional organic solvents.DESs not only have the characteristics of low cost,easy synthesis,and green but also have good solubility and adjustable physical and chemical properties.In this paper,two simple,green,and efficient methods for the analysis of heavy metal elements in various environmental samples were proposed by using eutectic solvent as extractant combined with MSPE and SFO-LPME.The main work was summarized as follows:1、Choline chloride(ChCl)was used as the hydrogen bond acceptor(HBA),and a variety of alcohols,amines,and carboxylic acids were used as hydrogen bond donors(HBD)to synthesized extractants DESs.Due to the hydrophilicity of DESs,magnetic nanoparticles of ferric oxide(nano-Fe3O4)were used as extractant carrier for recovery,combined with inductively coupled plasma-atomic emission spectrometry(ICP-OES)to analyze copper and lead in environmental samples.During the elution process,the HNO3 solution was selected to elute the metal ions captured by the adsorbent.After several experimental conditions were optimized,the limit of detection(LOD)were 0.29 ng mL-1 and 0.51 ng mL-1,and the maximum adsorption capacity of the adsorbent were 21.67 mg g-1 and 31.36 mg g-1 for copper and lead,respectively.Finally,the method was successfully applied to the detection of trace copper and lead in a variety of real environmental samples with recoveries between 94.9%-102%.2、Tetrabutylammonium bromide(TBAB)was used as HBA,and a series of carboxylic acids were used as HBD to synthesized DESs.According to the requirements of SFO-LPME for extractants,DES with a suitable melting point,density,and water solubility were selected as extractants,combined with flame atomic absorption spectroscopy(FAAS)for the analysis of lead and cadmium in environmental water samples.During the extraction process,dithizone was added to the solution as ligands which can form a hydrophobic complex with metal ions.After several experimental conditions were optimized,the limits of detection(LOD)were 0.73 ng mL-1 and 0.18 ng mL-1,and enrichment factors(EF)were 179 and 175 for Pb and Cd,respectively.Finally,the proposed method has been successfully applied to the detection of trace lead and cadmium in a variety of real environmental water samples with recoveries between 96.2%and 106%.