Development Of Measurement Technology And Certified Reference Materials Of Endocrine Disruptors And Aflatoxins In Typical Food

Contaminants in food is a key food safety concern worldwide.Endogenous exogenous contaminants are a serious health hazard due to their widespread contamination and long-term effects.Among them,aflatoxins are of great concern due to their high toxicity.Traditional liquid-liquid extraction,solid-phase extraction and gel permeation chromatography methods have low extraction efficiency and cumbersome operation,so the establishment of convenient and effective methods is a hot research topic.The establishment of simultaneous detection techniques for multiple types of endocrine disruptors is of great significance in addressing the accurate measurement of endocrine disruptors in food.Focusing on the needs of contaminant detection and metrological traceability,this thesis investigates the highly accurate measurement methods for aflatoxins in vegetable oil matrix and multi-component endocrine disruptors in milk powder.In order to guarantee the accuracy,reliability and traceability of typical contaminant detection results,certified reference materials were also highly needed.The main elements are as follows:1.Development of a rapid and accurate method for the accurate quantification of aflatoxin B₁（AFB₁）,aflatoxin B₂（AFB₂）,aflatoxin G₁（AFG₁）,aflatoxin G₂（AFG₂）in vegetable oils based on magnetic solid phase extraction（MSPE）-isotope dilution mass spectrometry（IDMS）.A novel cobalt magnetic based nanomaterial Co@Si O2@C was synthesised and characterised by XPS spectroscopy,transmission electron microscopy and Raman spectroscopy.The linear range of the four aflatoxins was 0.5μg/kg～50μg/kg with linearity coefficients greater than 0.99.The limits of quantification were 0.1～0.2μg/kg,and the recoveries ranged from 95.3～103.5%.The recoveries ranged from95.3 to 103.5%with the precision less than 4.3%.The results indicate that this method can meet the requirements for the analysis of aflatoxins in vegetable oils.Compared with the conventional method,the material showed good specificity and the matrix effect was less than 11%.The method provides a novel material for rapid pre-treatment of aflatoxins in food.2.Standard reference materials are essential for the accurate determination of endocrine disrupters in milk powder.Among them,purity reference standards are the source of metrological traceability.To overcome the lack of purity standards,this study was carried out to investigate the purity of 4-n-octylphenol,4-nonylphenol,ethinylestradiol,hexestrol and dienestrol using differential scanning calorimetry（DSC）.The study focused on optimising the heating procedure,heating rate and weighing volume.The results show that compounds such as 4-nonylphenol,which are thermally stable and have a simple structure,can be used for purity determination by DSC and the results are in good agreement with liquid chromatography.However,for thermally unstable substances,which are susceptible to thermal decomposition during melting,the purity cannot be determined by the DSC method.This work is the first to apply the DSC method to the purity determination of new impurities such as 4-n-octylphenol and 4-nonylphenol,and provides technical support for the development of purity standards3.In order to accurately quantify multi-component endocrine disruptors,an analytical method was developed for the accurate determination of 12endocrine disruptors from four major groups,including bisphenols,alkylphenols,endogenous estrogens and hormones,in milk powder using a dual-phase salinisation-solid-phase extraction clean-up method combined with isotope dilution high-performance liquid chromatography-mass spectrometry（IDMS-HPLC-MS/MS）.The effects of the mass spectrometric detection method,the chromatographic separation conditions,the extraction and purification methods and the type of filter membrane on the measurement results were investigated in detail.The method solves the problem of detecting a single type of endocrine disruptor and fills the gap for the simultaneous detection of multiple components of endocrine disruptors.The method laid the foundation for the subsequent development of multi-component endocrine disruptor standards.4.The reference material of four endocrine disruptor（hexestrol,dexamethasone,17β-estradiol and estriol）in milk powder was developed.The samples were purified by biphasic salting and solid phase extraction and determined by high performance liquid chromatography-isotope dilution mass spectrometry（HPLC-ID-MS/MS）,and the homogeneity and stability of the milk powder samples were checked and the uncertainties assessed.The homogeneity and stability of the standard were good,and the determination met the specifications and traceability requirements,filling the gap of multi-component matrix standards in China.The standard is suitable for method validation and quality control of relevant components in milk powder.