Study On Enrichment Of Arsenic And Mercury By Ultrasonic Assisted Enzymatic Extraction And Magnetic Solid Phase Extraction Technology

For the accuracy of heavy metal detection in Complex or ultratrace samples,the chose of suitable pretreatment is of great significance.Herein,current situation and the risk of heavy metal and several pretreatment technologies were summarized.Besides,the application of ultrasonic-assisted enzymatic digestion and magnetic nano-materials were described in detail.Meanwhile,The experiment about extraction and enrichment of As in Chinese medicine by ultrasonic assisted enzymatic extraction,and As and Hg in simulated water by magnetic solid phase extraction,which combined with atomic fluorescence spectrometry were carried out.The contents are as follows:Firstly,ultrasonic was applied to improve the traditional extraction of As in Codonopsis pilosula.The factors such as the type of extractant,the concentration of extractants,extract time,operating temperature and ultrasonic conditions were optimized.Under the optimal conditions,the extraction efficiency of As was incresed to 96.37%with the ultrasonic assisted enzyme extraction,which showed an only68.15%percentage extraction value of As in Codonopsis pilosula with solvent extraction.Besides,when ultrasonic assisted enzyme extraction is used,with the increase of ultrasonic power from 30W to 100W,an increase of 72.16%on extraction efficiency was observed.Moreover,the further digested was applied after ultrasonic assisted enzyme extraction suggested an increase on the stability of the detection and a decrease on interfere,which caused by residue after enzymatic hydrolysis.Secondly,Fe₃O₄@Au magnetic materials were obtained successfully by self-assembly method,and characterized by XRD,SEM,TEM and FT-IR.It was found that the size of Fe₃O₄ particle was about 500 nm,and the size of Au particle was about 10nm.The material was then applied into the extraction of Hg?II?,As?III?and As?V?in simulated water,which detected by atomic fluorescence spectrometry.The results showed that the fluorescence signal is in good linearity?R²>0.99?in the range of 0.2-2.5?g L^-1,0.2-2.5?g L^-1 and 0.02-0.8?g L^-1 for As?III?,As?V?and Hg?II?after an enrichment of 16 min,respectively.With the combination of hydride vapor generation and atomic fluorescence spectrometry,the detection limits for Hg?II?,As?III?and As?V?were 9.2 ng L^-1,8.5 ng L^-1 and 2.5 ng L^-1,and the relative standard deviations were 1.83%,2.74%and 3.94%,respectively,the recovery of Hg?II?,As?III?and As?V?were 94.9%¹02.4%.Finally,Fe₃O₄@g-C₃N₄ synthesized by solvothermal method.Through the characterization of XRD,SEM,TEM and FT-IR,it is indicated that the prepared g-C₃N₄ has a layered structure,and the Fe₃O₄@g-C₃N₄ composite with a particle size of about 200nm has been successfully obtained.The material was then shown to adsorb ultratrace Hg?II?species in simulated water combined with atomic fluorescence spectrometry.The result suggested that the Fe₃O₄ with 30%percentage of g-C₃N₄ obtained at 200?for 6 h showed an 95.46%percentage extraction value of Hg?II?in simulated water.The expeinment conditions were then optimized,under the optimal conditions,the enrichment efficiency of the material is higher than 99%.The recovery of Hg?II?was still above 80%when the material reused after three times.