Study On Rapid Identification Of Endogenous Quality And Exogenous Heavy Metals In Food And Herb Based On Nano-effect Fluorescence Sensing

The quality and safety of food and herb is a major issue concerning the national economy and people's livelihood,as well as the major national strategic needs(the four aspects should be implemented,especially the life and health of the people).Endogenous quality and exogenous heavy metal pollution are important problems in the quality and safety of food and herb.Among them,endogenous quality(the quality differences of endogenous components,functional characteristics,flavor,and taste)is mainly affected by different origins,brands,and aging years.Exogenous heavy metal pollution mainly comes from environmental factors such as sewage irrigation and waste gas discharge.Therefore,it is of great practical significance and value to develop sensitive,specific,and convenient methods for the rapid and accurate detection of endogenous quality and exogenous heavy metal pollution of food and herb for improving food and herb safety.This paper summarizes the recent worldwide literature on the detection and analysis of endogenous quality and exogenous heavy metals in food and herb.Accordingly,a series of new methods based on nano-effect fluorescence sensing analysis was developed and successfully applied to the rapid detection of food and herb endogenous quality and exogenous heavy metal pollution.The main research contents were as follows:(1)Firstly,the home and abroad modern instrumental analysis methods and their advantages and disadvantages for the identification of endogenous quality and exogenous heavy metals of food and herb were summarized.Then,the current research status and development direction of the fluorescence sensing method and its application in food and herb quality and safety detection were described.Finally,the research content and characteristics of this paper were put forward.(2)The traditional single fluorescence spectrum detection method in endogenous quality of food and herb identification has the problems of serious peak overlap and difficulty in the extraction and screening of subtle spectral difference information.In this study,36 kinds of CRP from different origins and18 kinds of CRC from different aging years were used as research objects.Combining with the partial least squares discriminant analysis(PLSDA),a novel nano-effect splicing fluorescence sensing method based on Cd Te and Au NPs was established.The results showed that the recognition accuracy of origin and aging year of CRP and CRC could be increased from 95.10%and 66.67%to100%and 98.04%,respectively.Further studies showed that the specificity and sensitivity of the mentioned fluorescence sensing were mainly due to the interaction between the nanometer sensing materials(Cd Te and Au NPs)and polymethoxylated flavones in CRP,as well as the integration and amplification of the differential information of fluorescence spectrum by the splicing strategy.Compared with the single original fluorescence spectrometric method,this method improves the specificity of sensing and the amount of information extracted from food and herb samples and can obtain a better identification effect.It provides a new idea for the rapid identification and analysis of food and herb endogenous quality.(3)Based on maintaining high accuracy in the identification method of food and herb endogenous quality,the portability of the instrument needed for the detection method of the nano-effect fluorescence spectrum was improved.In this work,a novel fluorescence colorimetric array sensing method based on acid-sensitive Cd Te quantum dots was established by combining the classical hierarchical cluster analysis(HCA)and partial least squares discriminant analysis(PLSDA)with 32 kinds of Chinese traditional grain vinegar of different brands and aging years.The results showed that the method used the RGB signal in the colorimetric array to simultaneously characterize the different information of characteristic components in different CTCV samples.It realized the rapid identification of CTCV of different brands and aging years,and the discriminant result reached 100%.The specificity of this system is reflected in the polymerization effect of Cd Te quantum dots under acidic conditions and the interaction between Cd Te quantum dots and acid ions.This method is simple,convenient and rapid,and only needs portable devices such as cameras or smartphones.It is expected to be extended to the endogenous quality identification system of food and herb rich in organic acids,such as salvia miltiorrhiza,honeysuckle,and angelica.(4)In order to further improve the visual effect of the fluorescence colorimetric array sensing method,a new visual fluorescence sensing method based on the aluminum-gold nanocluster(Al@Au NCs)complex was established with 60 batches of chrysanthemum morifolium from different origins as the research object.The results showed that the method could amplify the difference information of the characteristic components of flavonoids in chrysanthemum morifolium from different origins to produce rich color changes,and then obtain more obvious visual signals of fluorescent color changes(ranging from orange to purple and green)for intuitive qualitative discrimination.At the same time,PLSDA model was combined to verify the effect of the visual color change.The discriminant analysis results of the model based on Al@Au NCs visual fluorescence color difference can be improved from 46.15%of the original fluorescence color difference to 100%,which successfully realized the rapid and accurate identification of chrysanthemum from different origins.The specificity of the above mentioned method is mainly due to the excited state intramolecular proton transfer effect between 3-hydroxyflavone derivatives and Al³⁺,and the competitive interaction between flavonoids and Al@Au NCs.This method has the advantages of high sensitivity,high specificity,and good visualization effect,and can provide a new strategy for the visual identification of endogenous quality of food and herb rich in 3-hydroxyflavone derivatives.(5)The identification method of endogenous quality of food and herb mainly requires effective characterization and analysis of the overall differentiation characteristic information of chemical components rich in different samples.However,the identification methods of exogenous heavy metals need to put forward high requirements on the detection limit and selectivity of target detection substances.In this study,we established a highly sensitive and highly selective dual-QDs ratio fluorescence sensing method for the detection of Ag⁺contamination in food and herb.By using the ratio fluorescence self-correction and the interaction of surface functional groups of dual-QDs,we realized the accurate identification of Ag⁺contamination in complex samples such as CRP and tea.The results showed that the linear range of Ag⁺detection was 0-800 nmol/L,with a LOD of 7.7 nmol/L,far below the limit of 900 nmol/L set by the U.S.Environmental Protection Agency(EPA).In this research,Ag⁺aggregates on the surface of the dual-QDs through the electron transfer effect,which reduces the stability and activity of the dual-QDs,and makes the fluorescence in the turn-off sensing mode to achieve the detection purpose.Compared with traditional single quantum dot sensing,this method has a stronger anti-interference ability and higher specificity,which provides a new way for the detection of Ag⁺in complex food and herb samples.(6)To further optimize the specificity of the turn-off sensing method based on fluorescence,enhance the anti-interference ability of the detection of heavy metals.In this study,a new reversible fluorescence turn-off-on sensing method based on sulfur-doping carbon dots(SCDs)and thiophanate methyl(TM)was established to accurately identify Hg²⁺contamination in complex samples such as CRP and grape juice.The results showed that the linear range and LOD of Hg²⁺can reach 50.0-5800 nmol/L and 33.3 nmol/L,respectively,which met the requirements of the Chinese national standard(50-500 nmol/L).In this system,SCDs fluorescence turn-off-on sensing mode generated by the reversible S-Hg bond in SCDs-Hg-TM and TM-Hg precipitation generated by the specific polymerization between TM and Hg²⁺,thus achieving the dual purpose of rapid detection and removal of Hg²⁺.This method can provide theoretical guidance and new ideas for the rapid detection and impurity removal process of Hg²⁺in food and herb complex systems.(7)For the realization of the simultaneous visual detection of various heavy metal contamination in food and herb with Cd²⁺,Pb²⁺,and Hg²⁺pollution as the research object.Based on the previously established nano-effect fluorescence sensing methods,a new three-channel visualized fluorescence array sensing method consisting of gold nanoclusters(Au NCs)nitrogen-doping carbon dots(NCDs)and their complexes(Au NCs@NCDs)was designed and constructed.The direct visual semi-quantitative identification of Cd²⁺,Pb²⁺,and Hg²⁺in complex samples of CRP,chrysanthemum,lily and atractylodes was realized.At the same time,the visual discrimination effect was verified and the accurate quantitative analysis was realized by combining it with chemometrics.The results showed that the linear range and LOD of the three heavy metals were0.38-338?mol/L and 0.15?mol/L(Cd²⁺),0.75-60?mol/L and 0.20?mol/L(Pb²⁺),0.15-7.50?mol/L and 0.09?mol/L(Hg²⁺),respectively,which met the requirements of the Chinese national standard.This research system is based on the aggregation induced fluorescence enhancement(AIE)effect of Au NCs,electron transfer(ET)effect of NCDs,and fluorescence resonance energy transfer(FRET)effect between Au NCs@NCDs to realize the simultaneous visual and specific recognition of a variety of heavy metals.At the same time,in the process of recognition of Cd²⁺and Pb²⁺by Au NCs,an obvious Tyndall effect was produced,and the removal of Cd²⁺and Pb²⁺could be achieved by simple centrifugation or static treatment.This method is simple,rapid,sensitive,highly selective,and has the characteristics of visual effect and impurity removal at the same time.It is expected to be widely used as an on-site or real-time detection technology for the monitoring of heavy metals in various foods and herbs.