Separation And Detection Of Aflatoxins And Carotenes In Food Samples

Due to the complexity of sample matrices,the structural diversity of components and the variety and low concentration of risk factors,modern separation and analytical techniques with superior performance are required for ensuring the safety and nutrition of food products.As an effective separation and analysis technique,high-performance liquid chromatography（HPLC）is widely used for the detection and evaluation of nutritional components in food,and the tracing and prevention of hazards and risk factors.In this article,mycotoxins in cereals and carotene in red palm oil were separated and analyzed by HPLC.Main contents are as follows:1.Preparation of chitosan hydrogel by blending strategy and extraction of aflatoxin from cereals:Fe₃O₄ magnetic nanoparticles and metal organic framework Ui O-66-NH₂ were evenly dispersed in the acetic acid solution of chitosan,and then dropped into the alkali solution through a syringe,and Fe₃O₄/Ui O-66@CS chitosan based composite hydrogel was prepared by blending strategy and characterized by SEM,ATR-FTIR,XRD,VSM and TGA,which confirmed the successful preparation of Fe₃O₄/Ui O-66@CS composite gel.Four aflatoxins in cereals were extracted and determined by combining magnetic solid phase extraction（MSPE）and HPLC-FLR.The parameters affecting extraction efficiency were optimized,including amount of adsorbent,extraction time,temperature,solution p H,type of desorption solvent,and desorption time.Under optimized conditions,the established MSPE-HPLC-FLR method had good linearity（AFTB1 and AFTG1,0.5-50.0 ng/m L;AFTB2 and AFTG2,0.1-20.0ng/m L）,with R² ranging from 0.9984 to 0.9997.The detection limits for AFTB1,AFTB2,AFTG1,and AFTG2 are 0.09 ng/m L,0.02 ng/m L,0.10 ng/m L,and 0.01 ng/m L,respectively.This method could be successfully used for the extraction,enrichment,and detection of four aflatoxins in grains（rice,glutinous rice,wheat,and soybean）.The spiked recovery was70.8%～117.0%,and the relative standard deviation was 1.7%～15.0%（n=5）.The results fully meeting the requirement of National Standard GB 2761—2017 for the limited detection of aflatoxins in food.2.Preparation of chitosan hydrogel by in situ method and its extraction performance for aflatoxin from Cereals:Fe₃O₄ magnetic nanoparticles,1-butyl-trimethylimidazole bromide ionic liquid（IL）and metal ion Zr⁴⁺were evenly dispersed in the acetic acid solution of chitosan,and dropped into the alkali solution through a syringe to form chitosan hydrogel.Then the prepared microspheres were combined with the ligand 2-aminoterephthalic acid to generate metal organic framework Ui O-66-NH₂ by solvothermal method,thus obtaining Fe₃O₄/Ui O-66/IL@CS by in-situ synthesis method.The structure and composition of the composite hydrogel were characterized by SEM mapping,ATR-FTIR,VSM,TGA and other advanced technologies.were characterized by SEM,ATR-FTIR,VSM,TGA and other advanced technologies.The composite hydrogel was used as the adsorbent of MSPE,and the important parameters affecting the extraction efficiency（amount of adsorbent,extraction time,ionic strength,type of desorption solvent and desorption time）were optimized.Under optimized conditions,a method for extracting and determining aflatoxin was established by combining with HPLC-FLR.The linear range of AFTB1 and AFTG1 were 0.2～100.0 ng/m L,while the linear range of AFTB2 and AFTG2 were 0.06～30.0 ng/m L,with a correlation coefficient（R²）greater than 0.9982 and a low detection limit（0.01 ng/m L～0.07 ng/m L）.This method could be successfully used for the separation and detection of aflatoxin in grains（rice,glutinous rice,wheat,soybeans,paddy,corn）,and the spiked recovery was 77.3%～118.6%,with the relative standard deviation of 1.0%～11.7%（n=5）.The composite hydrogel prepared by in-situ synthesis was more uniform than that prepared by blending strategy,and the introduction of IL further enriched the interaction sites between the composite hydrogel and aflatoxin.3.High-performance liquid chromatographic separation of four carotene isomers（α-carotene,all-trans-β-carotene,13-cis-β-carotene,9-cis-β-carotene）in red palm oil was optimized in detail.On three chromatographic columns including Inert Sustain C18,Welch Ultimate XB-C30 and YMC-C30,the effects of mobile phase type,elution mode,mobile phase ratio,flow rate,and column temperature on the separation of four target analytes were discussed.The optimized chromatographic conditions were as follows:（YMC-C30 as chromatographic column,dichloromethane/acetonitrile/methanol（20.5/15/64.5,v/v/v）as mobile phase,isocratic elution mode,1.2 m L/min of flow rate,25°C of column temperature）.Under the optimized chromatographic conditions,four carotene isomers in red palm oil were successfully separated and the analytical features of proposed method were evaluated.The method showed a good linear relationship in the range of 0.2～3.0μg/m L with a correlation coefficient（R²）ranging between 0.9996 and 0.9999.The limit of detection,defined as a signal-to-noise ratio（S/N）of 3,was 0.01μg/m L.After being treated by ethanol extraction and saponification,the contents of four carotene isomers in real red palm oil samples were determined.The spiked recoveries of four carotene isomers in red palm oil were91.2%～116.0%,and with the relative standard deviations（RSD）from 2.3%to 8.5%（n=5）.The results indicated that the proposed method could be successfully used for the separation and detection of four carotene isomers in red palm oil,and had great application potential in the quality analysis of red palm oil.