Study On Determination Method And Risk Assessment Of Mycotoxins

Mycotoxins are secondary metabolites produced by several toxigenic fungi under suitable conditions,which can directly contaminate grains,fruits,vegetables and traditional Chinese medicines,causing the adverse effects on animal and human health through the food chain.Due to the favorable temperature and humidity conditions conducive to the production of fungi,mycotoxins contamination easily occurs in the Yangtze River Delta region.Therefore,it is important to establish rapid,sensitive and accurate analytical methods,reasonable risk assessment models and effective degradation technologies of mycotoxins for food and drug quality control and further safeguarding human health.However,there are still some technical difficulties in the existing research.First,there are a few rapid detection technologies for mycotoxins based on portable instrument with no need for requiring laborious pretreatment process and large equipments,which remains highly in point-of-use test systems challenging;Second,more than 400 mycotoxins have been identified,and it is common to be contaminated by multiple mycotoxins in different matrix.But most of research only focused on one or one type mycotoxins,the new types of mycotoxins(unknown toxins,the new mycotoxins found in different agricultural products)were neglected,thus it is still lack of appropriate efficient broad-spectrum screening methods for mycotoxins in different matrices;In addition,the current risk assessment models for mycotoxins are only for the single toxin,ignoring the cumulative risks of the co-cotamination of multiple mycotoxins.Finally,using physical,chemical and biological methods to reduce the contamination of common mycotoxins may cause additional contaminations and be restricted by large-scale application,so it is more important to adopt green,efficient and safe degradation technology.In this thesis,we established the 174 mycotoxins database,and non-targeted screening technology for common and new mycotoxins in gains and traditional Chinese medicine.According the results,we also built an electrochemical detection technology for rapid detection of patulin which is commonly contaminated in hawthorn.These high sensitive and rapid detection methods of mycotoxins can be applied in mycotoxins early warning.Then,we established the risk assessment models to evaluate the cumulative risks of co-contaminations of different mycotoxins,predicting the exposure risks of people to a variety of mycotoxins.Finally,the photodegradation method was developed to degrade and reduce the side effects of the typical mycotoxin in gain samples.The main research contents and results are as follows:1.An ultra-high performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry(UHPLC-Q-TOF-MS)screening technique for 174mycotoxins(prototype,novel and related derivatives)was established.The samples were extracted with acetonitrile containing 1%acetic acid and purified with Qu ECh ERS.An acquity UPLC BEH C₁₈ chromatographic column(100 mm×2.1 mm,1.7 mm)was used for separation.The mobile phase consisted of(A)water containing 1%formic acid and 3mmol/L ammonium acetate and(B)acetonitrile with the linear gradient elution program,followed by analysis with Q-TOF-MS.According to the high resolution molecular ion peak,isotope distribution and characteristic ion information of mycotoxins,the 174 kinds of mycotoxins database was established,and the Master View software was used to achieve the qualitative detection.The quantification of 20 mycotoxins was also investigated by UHPLC-Q-TOF-MS.The results indicated that the 20 mycotoxins had good linear relationships(R²>0.97),and the accurate mass errors were lower than 5 ppm in wheat,corn and hawthorn sample.The limit of quantification ranged from 0.5?g/kg to 20?g/kg,the recovery is 70.16-119.7%with the relative standard deviation of 0.21-14.97%.The established method was used to analyse the multipul mycotoxins in 119wheat samples,32 corn samples and 31 hawthorn samples,and 41,22 and 27 kinds of mycotoxins were contaminted,respectively.This method could provide an important basis for the high-throughput and confirmatory method for the determination of multipul mycotoxin in cereals and traditional Chinese medicines.2.Rapid detection of patulin in juice by electrochemical sensor.An innovative approach based on a surface functional monomer-directing strategy for the construction of a sensitive and selective molecularly imprinted electrochemical sensor for patulin recognition is proposed.A patulin imprinted platinum nanoparticle(Pt NP)-coated poly(thionine)film was grown on a pre-formed thionine tailed surface of Pt NP-nitrogen-doped graphene(NGE)by electropolymerization,which provided high capacity and fast kinetics to uptake patulin molecules.Thionine acted not only as a functional monomer for molecularly imprinted polymer(MIP),but also as a signal indicator.Enhanced sensitivity was obtained by combining the excellent electric conductivity of Pt NPs,NGE and thionine with multi-signal amplification.The designed sensor displayed excellent performance for patulin detection over the range of 0.002-2 ng/m L(R²=0.995)with a detection limit of 0.001 ng/m L for patulin.In addition,the sensor showed good stability and high repeatability and selectivity.Furthermore,the feasibility of its applications has also been demonstrated in the analysis of real samples,providing novel tactics for the rational design of MIP-based electrochemical sensors to detect a growing number of deleterious substances.3.Exposure assessment and cumulative health risk assessment of multiple mycotoxin biomarkers in residents of the Yangtze River Delta,China.This biomonitoring study was conducted to investigate exposure to 23 mycotoxins/metabolites and their determinants in 227 adults(aged 20-88 years)in the Yangtze River Delta(China)by UHPLC-MS/MS method.Eight mycotoxins were detected in 110 urine samples,and multiple mycotoxins co-occurred in 51/227(22.47%)of urine samples,with deoxynivalenol(DON),fumonisin B1(FB1),and zearalenone(ZEN)being the most frequently occurring.For single mycotoxin risk assessment,the FB1,ZEN,aflatoxin B1(AFB1)and ochratoxin A(OTA)all showed potential adverse effects.However,for the12 samples containing DON and ZEN,in which none had a hazard risk,the combination of both mycotoxins in 2 samples was considered to pose potential endocrine disrupting risks to humans by hazard index(HI)method.The combined margin of exposure(MOE_T)for the AFB1 and FB1 could constitute a potential health concern and AFB1 was the main contributor.Our approach provides a blueprint for evaluating the cumulative risks related to different types of mycotoxins,and opens a new horizon for the accurate interpretation of epidemiological health outcomes related to multi-mycotoxin exposure.4.The photodegradation behaviors and mechanisms of tentoxin(TEN),an important mycotoxin frequently found in agro-foods were investigated in water environment.After investigation of different light sources,radiation times,initial concentrations and p H values,the highest degradation rate of TEN is shown under the full band spectrum condition rather than UV and visible light irradiation,and the concentrations of TEN decreased with the extension of degradation time.However,light intensity and p H value of the solution exibited no significant relationship with the degradation of TEN.When p H was 6,the initial concententration of toxin was 1.0?g/m L and the Xenon lamp power was 540 W,the degradation rate of TEN was 55.90%.Then,UHPLC-Q-TOF-MS was used to identify the degradation products.It was found that TEN would rearrange itself under light conditions and generate trans isomers.The products were less toxic than TEN and showed partial detoxification effects.