Study On Identification And Pollution Of Typical Mycotoxins In Grains In Yangtze River Delta Region

Mycotoxins are a class of secondary metabolites produced by fungi under appropriate temperature and humidity conditions.They may form on grains and seriously affect the quality of the grains.Due to the high incidences of mycotoxins in the natural environment and its difficulty in natural degradation,they could be continuously accumulated in the host,and then be transmitted and accumulated in animals and humans through the food chain pathway,leading to severe liver and kidney function damage,carcinogenesis,teratogenicity,and other huge toxic hazards.Therefore,it is an critical issue to establish the high-sensitivity and high-throughput analytical methods for simultaneous determination of multi-mycotoxin to effectively monitor the level of mycotoxins in agricultural products,so as to reduce the risk of human exposure.The main researches are described in details as follows:1. Establishment of an ultra-high performance liquid chromatography-tandem mass spectrometry method for simultaneous detection of 40 mycotoxins in grainsIn the present study,an analytical method for simultaneous determination of 40mycotoxins in different crops was developed based on a Qu ECh ERS pretreatment procedure coupled with ultra-high performance liquid chromatography-tandem mass spectrometry?UHPLC-MS/MS?.The samples were extracted with 5 m L water and 8m L acetonitrile containing 1%?v/v?formic acid.An aliquot of the supernatant was dried by nitrogen gas,re-dissolved in 1 m L water containing 5 mmol L^-1 ammonium acetate-acetonitrile?80:20,v/v?,and analyzed by UHPLC-MS/MS.Accurate quantification was achieved by matrix-matched calibration curves and isotope internal standards.The recovery ranges of different mycotoxins in spiked wheat,maize and rice samples were75.8?111.4%,73.7?117.8%and 75.2?111.6%,respectively?n=5?.Good linear relationships were obtained and the correlation coefficients?R²?were greater than 0.99.The limits of detection?LODs,S/N=3?and the limits of quantification?LOQs,S/N=10?in different matrices ranged from 0.2?g L^-1 to 5?g L^-1 and from 0.5?g L^-1 to 10 ?g L^-1,respectively with the precisions in the range of 1.1?16.0%.The proposed method is simple and rapid which could provide a powerful tool for quantitative analysis of the 40 mycotoxins in various grain samples compared with the national standard.2. Pollution of multi-mycotoxins in grains in Yangtze River Delta RegionIn order to figure out the contamination of mycotoxins in grains,360 grain samples including wheat?120?,maize?120?and rice?120?were collected from 4 provinces?Anhui,Jiangsu,Shanghai and Zhejiang?in Yangtze River Delta region in 2019.In wheat,the most frequently found mycotoxins were altenuene?ALT?,tentoxin?TEN?and tenuazonic acid?Te A?with the incidence of 100.00%and the average concentrations of 31.27,20.50 and 91.19?g kg^-1,respectively.The exceeding rate of deoxynevalenol?DON?in wheat was 0.83%(1002.20?g kg^-1).In maize,the highest incidence of mycotoxin was found for ALT?98.33%?with an average concentration10.83?g kg^-1.A total of 5.00%samples contained AFB₁ with the concentrations over the regulations.ALT was found to be the most frequent contaminant with the incidence of 100.00%in rice,and the average concentration of 12.11?g kg^-1.The grain samples surveyed in this study were all contaminated with more than one mycotoxins,even up to 15 kinds of mycotoxins,indicating that the presence of multiple mycotoxins in grains may cause harmful effects to human health.3. Development of an electrochemical method for rapid simultaneous detection of zearalenone and fumonisin B₁ in maizeBased on the investigations of mycotoxins in grains in Yangtze River Delta,zearalenone?ZEN?and fumonisin B₁?FB₁?were frequently found in maize,with the incidences of of 53.33%and 81.67%,respectively.In this study,co-reduced molybdenum disulfide and gold nanoparticles?r Mo S₂-Au?were designed and used for the first time as an efficient platform endowing electrochemical electrodes with superior electron transfer rates,large surface areas and strong abilities to firmly couple with large amounts of different aptamers.After further modification with thionine?Thi?and6-?Ferrocenyl?hexanethiol?FC6S?,a platform enabling sensitive,selective and simultaneous determination of two important mycotoxins,zearalenone?ZEN?and fumonisin B₁?FB₁?,was achieved.The established aptasensor showed excellent linear relationships?R²>0.99?when ZEN and FB₁ concentrations were in the range of 1×10^-3?10² ng m L^-1 and 1×10^-3?1×10 ng m L^-1,respectively.High sensitivity of ZEN and FB₁ with a limit of detection as low as 5×10^-4 ng m L^-1was obtained with excellent selectivity and stability.The effectiveness of the aptasensor was verified in real maize samples,and satisfactory recoveries were attained.The established platform could be easily expanded to other aptamer-based multiplex screening protocols in biochemical research and clinical diagnosis.