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Rapid And Sensitive Detection Of New Red By Surface-enhanced Raman Spectroscopy Combined With Molecularly Imprinted Technique

Posted on:2021-02-08Degree:MasterType:Thesis
Country:ChinaCandidate:K Y XuFull Text:PDF
GTID:2381330623967459Subject:Food processing and safety
Abstract/Summary:PDF Full Text Request
New Red pigment has been widely used in food industry due to its advantages of good stability,strong coloring power and low cost.However,illegal traders often add excessive New Red to some food products,which cause potential hazards to human body such as allergic sensitization,mutagenicity,carcinogenicity and hyperactivity of children.There are many deficiencies in the current detection methods of New Red including complicated operation,time-consuming pretreatment process,not portable instrument,high detection cost,difficulty in outdoor field detection,etc.Therefore,it is of great significance to establish a simple,rapid,high sensitivity and high selectivity analysis method for on-site detection of New Red.Surface-enhanced Raman spectroscopy?SERS?is a fast,on-site detection technique featured with high sensitivity,short detection time,simple operation and portable instruments.However,SERS suffers from the interference in complex food matrix,which is difficult to identify and detect target analytes with high selectivity.Molecularly imprinted hydrogels?MIHs?prepared by molecularly imprinted technique?MIT?have high selectivity and can efficiently identify,extract and enrich target analytes in complex matrices.Based on the above background,this work combines the highly sensitive SERS technique with the highly selective MIHs technique.A molecularly imprinted hydrogel containing positively charged gold nanoparticles and negatively charged New Red molecules resulted from its sulfonate?SO3-?group was constructed via electrostatic force.The MIHs were then used as a SERS active substrate for highly sensitive,selective,low-cost,on-site and rapid detection technique of New Red.The thesis primarily covers following aspects:?1?Negatively charged gold nanoparticles based on sodium citrate reduction method and positively charged gold nanoparticles via mercaptoethylamine modification were prepared.The two types of gold nanoparticles were characterized by transmission electron microscope?TEM?,dynamic light scattering?DLS?,energy dispersive X-ray?EDX?spectroscopy and SERS,etc.The results show that positively charged gold nanoparticles have significant SERS enhancement effect on New Red molecules,while negatively charged gold nanoparticles have no SERS enhancement effect.The positively charged gold nanoparticles with an average particle size of 49.0nm showed the highest enhancement effect.These positively charged gold nanoparticle was used as SERS substrate to directly detect the New Red aqueous solution.The corresponding detection limit was 6.25 ng/mL with the detection linear range of 0.10-10.0?g/mL.The sample recovery rate was 99.3%-102.0%,and the relative standard deviation?RSD?was 0.5%-6.4%.?2?A New Red molecularly imprinted hydrogel containing positively charged gold nanoparticles using acrylamide?AM?as the functional monomer,New Red pigment as the template molecule,N,N'-methylene bisacrylamide as the cross linker,potassium persulfate as the initiator were prepared by free radical polymerization.The imprinted hydrogels were evaluated by selective adsorption and specific adsorption experiments.The imprinted hydrogels were further employed as the SERS substrate to adsorb and detect New Red in aqueous solution.The corresponding detection limit of New Red was 0.10?g/mL with the detection linear range of 1.0-100.0?g/mL.The sample recovery rate was 86.3%-100.6%and the relative standard deviation?RSD?was 2.3%-7.7%.?3?The molecularly imprinted hydrogels were also applied to adsorb and detect New Red in the complex matrix?New Red spiked in sports drinks?.The detection recovery rate of the sample was 91.0%-97.1%,and the relative standard deviation?RSD?was 1.8%-7.7%.The good recovery rate and low relative standard deviation value of samples show that the MIHs prepared in this work is suitable for the detection of New Red in real samples.
Keywords/Search Tags:surface enhanced Raman spectroscopy, molecularly imprinted hydrogels, detection, New Red, gold nanoparticles
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