Application Of Magnetic Nanocomposites In Detection And Removal Of Mycotoxins In Typicalagricultural Products

The country is people-oriented,the people are food oriented,and food safety and quality come first.The quality and safety of agricultural products is directly related to the life safety,the healthy development of agriculture and stability of society.Mycotoxins are toxic secondary metabolites formed and released by many fungal species,its toxic effects can be divided into teratogenic,carcinogenic and mutagenic.Most of these mycotoxins are chemically stable and highly resistant even when cooked at high temperatures.Therefore,mycotoxins can easily enter the feed and food chain.At the same time,multiple mycotoxins may exist in the same sample leading to additive or even synergistic effects and increased toxic,resulting in a serious threat to human and animal health.As a powerful analytical tool,UPLC-MS/MS has frequently been used due to its high accuracy,specificity,and selectivity for the identification and quantification of multiple mycotoxins.The pretreatment technology is a necessary and key step in the whole process of sample analysis.The quality of pretreatment technology directly determines the selectivity,accuracy and sensitivity of analysis methods.Physical adsorptionis the most promising mycotoxin removal method forthe specificity,low cost,and high removal efficiency.This work focuseson development of accurate,efficient and sensitive detection and removal methods formycotoxins in agricultural products,and start with improving the sample pretreatment efficiency and adsorption efficiency,developthe pretreatment method and physical adsorption method based on magnetically controlled carbon nanomaterials,and realize the accurate,efficient and sensitive detection and removal of mycotoxins in agricultural products.The main research contents and results are as follows:（1）Firstly,the UPLC-MS/MS analysis method of multiple mycotoxins was established.Sample analysis was performed using a Waters ACQUITY UPLC system coupled to a triple quadrupole MS with an orthogonal Z-spray electrospray ion-ization（ESI）interface.The LC separation of 33 mycotoxins was performed on an ACQUITY CORTECS UPLC C18 column.Positive ion and negative ion modes were also implemented according to the structural features of the sample.The liquid phase conditions are as follows:column temperature 40℃,sample chamber temperature 4℃,injection volume 5μL.The mobile phase consisted of 1 m M NH₄AC（A）and Me OH（B）with a water flow of 0.3 m L/minin Milli-Q water.The established method can achieve accurate quantitative analysis of 33 mycotoxins within 9 minutes,and laid a methodological foundation for the study of mycotoxin sample pretreatment.（2）In this chapter,a series of different types of Fe₃O₄based nanoparticles modified with multiwalled carbon nanotubes（Fe₃O₄-MWCNTs）were designed as modified QuEChERS adsorbents forthe pretreatment of multiple mycotoxins in cereals.The extraction solvent type,type and amount of the Fe₃O₄-MWCNTs were systematically optimized.The method for the simultaneous determination of multiple mycotoxins in cereals was established by combining optimized modified QuEChERS method with UPLC-MS/MS.Under optimal conditions,the method was validated and showed satisfactory linearity（r²≥0.9965）,good recovery（73.5–112.9%）,good precision（1.3–12.7%）,and excellent sensitivity（ranging from 0.0021 to 5.4457 ng/g）.Therefore,Fe₃O₄-MWCNTs was selected as modified QuEChERS purification material,at the same time,Fe₃O₄-MWCNTs have good purification performance and magnetic separation characteristics,which can effectively shorten the sample pretreatment time and improve the sample pretreatment efficiency.The improved QuEChERS-UPLC-MS/MS analytical technology is simplicity,rapidity,economy and high efficiency,which can realize the simultaneous detection of multiple mycotoxins in large quantities of agricultural products.（3）During the work of risk assessment of agricultural products,it was found that agricultural products such as corn and wheat were serious polluted by ZEN and its isomer（α-ZOL,α-ZAL,β-ZAL,β-ZOL,ZAN）,and the prepared Fe₃O₄-MWCNTs cannot achieve effective pretreatment and purification for these mycotoxins with polyhydroxy.In order to realize the simultaneous detection of mycotoxins with polyhydroxy in agricultural products,Fe₃O₄/g-C₃N₄ nanocomposites were fabricated to employ as modified QuEChERS adsorbent.In addition,it is also used in conjunction with UPLC-MS/MS,an accurate quantitative approach to analyze 27 mycotoxins in agricultural products has been developed.Experiments proved that this method could exhibit good linearity under the appropriate and optimal external environment（r²≥0.9954）,high sensitivity（the limit of detection is 0.0004–0.6226 ng/g and the limit of quantitation is 0.0014–2.0753 ng/g）,adequate recoveries（77.81–115.21%）,and excellent repeatability（with a threshold of intra-day precision of 1.5–10.8%and inter-day precision in the range of 2.9–12.5%）.The 10 mycotoxins detected,including AFB1,OTA,and ZEN,were all higher than the national standard when the technique was later implemented to the detection of corn samples in practice.In order to improve food safety,the technique introduced in this study can also be utilized in the detection of a variety of mycotoxins in other agricultural products（e.g.rice,wheat and coix seed）.（4）Mycotoxins in plant-derived agricultural products are inevitable and widespread.It is very urgent and necessary to study effective detoxification technology of mycotoxins.In order to realize the effective removal of mycotoxin,the key is to design magnetic controlled nanomaterials with high specificity,good biocompatibility,strong adsorption capacity and reusable.In this chapter,the Fe3O4@Si O2-SH adsorbent was designed to remove PAT.The adsorption conditions,adsorption kinetics and adsorption thermodynamics were studied.The results showed that the adsorption process was spontaneous and endothermic,which could be well described by the Pseudo-second order model and Freundlich isotherm model.The maximum adsorption capacity was 2.463μg/mg,and the adsorption time was 8 h.After five cycle adsorption-desorption,Fe3O4@Si O2-SH still had high adsorption capacity for PAT,had no obvious toxicity to NIH 3T3 cells,and would not lead to the deterioration of the taste and quality of fruit juice.Therefore,the excellent adsorption performance,good repeatability,safety and applicability,which can ensure the application Fe3O4@Si O2-SH in PAT adsorption in actual apple juice industry.