Preparation Of Functionalized Fe₃O₄ Nanoparticles And Their Applications In Recognition And Enrichment Of Dyes And Mycotoxins In Food And Environment Samples

Magnetic nanoparticles?MNPs?not only have intrinsic characteristics with a high surface area-to-volume ratio,promising a much greater extraction capacity,and superparamagnet,separating easily under an external magnetic field,but also have other advantages,like environment friendly,easy preparation and good reusability.In addition,the surfaces of MNPs have many active groups,which enable facile functionalization to extract and enrich target compounds selectively.Thus,the MNPs are attracted much attention in pretreatment and analysis of samples.In our work,several kinds of functionalized core-shell Fe₃O₄ NPs were prepared and applied to the separation and enrichment of basic orange,ochratoxins and aflatoxin B from food and environment samples prior to determination by high-performance liquid chromatography?HPLC?.The main results are shown below:1.Research on functionalized Fe₃O₄ nanoparticles as adsorbents for removal of basic orange in foods with high-performance liquid chromatography analysis1)Sodium dodecyl sulfonate?SDS?coated Fe₃O₄ nanoparticles?Fe₃O₄NPs@SDS?were synthesized through using Fe₃O₄ nanoparticles as a carrier.Fe₃O₄NPs@SDS were used to extract and enrich cationic compounds basic orange 21?BO21?and basic orange 22?BO22?in dried beancurd stick,yellow fish,drinks and wine in the acid solution with pH 4.5,then separated quickly via an external magnetic field.BO21 and BO22 from Fe₃O₄ NPs@SDS were desorbed by 1 mL methanol and determined by HPLC.The results show that the good linearities for the two dyes were in the range of 0.02-5?g/mL with r of 0.9999.The detection limits were 0.88?g/kg for BO21 and 0.53?g/kg for BO22.The recoveries were in the range of 72.0-98.0%.The pretreatment method is simple operation,high enrichment efficiency with the maximum adsorption capacities of BO21 and BO22 for 76.8 and 93.5 mg/g,respectively.And the whole extraction time is no more than 13 min,which is more than 4 times shorter than that of the national standard method of China?60 min?.2)Magnetic molecularly imprinted polymers?BO2-Fe₃O₄@PDA MIPs?were prepared by self-polymerization of dopamine,forming the polymers layers with basic orange 2?BO2?as the template molecular on the surface of Fe₃O₄ NPs.Then the template molecular was eluted by 3%acetic acid-20%acetonitrile solution?v/v?.Through the study and optimization of the amount of the polymers,pH value,ultrasonic time and desorption,BO2 was extracted successfully by BO2-Fe₃O₄@PDA MIPs in food samples,such as dried beancurd stick,yellow fish,drinks,chilli powder and wine.Under the optimized conditions including 15 mg of BO2-Fe₃O₄@PDA MIPs,5.6 of pH,5 min of ultrasonic time and 2?1+1?mL of ethanol,the good linearity for BO2 was in the range of 0.04-1?g/mL with r of 0.9991.The detection limit was 5.8 ng/mL.The recoveries were 73.3-90.0%with relative standard deviation of 3.1-8.1%in food samples.And the maximum adsorption capacity of the polymers for BO2 was 24.4 mg/g.The simple and effective method fully shows the magnetic molecularly imprinted polymers characters with a specific adsorption property and a high surface area-to-volume ratio.2.Research on functionalized Fe₃O₄ nanoparticles as adsorbents for recognition and enrichment of ochratoxins prior to their determination by high-performance liquid chromatography1)The magnetic adsorbents of mixed hemimicelles?Fe₃O₄/SiO₂ NPs@CPC?were formed through functionalizing the surfaces of silica-coated Fe₃O₄ NPs with cetylpyridinium chloride?CPC?.Based on electrostatic and hydrophobic interactions between the mixed hemimicelles and ochratoxin A?OTA?,the pretreatment method was developed for extraction and enrichment of OTA.Various factors affecting the extraction efficiencies were investigated.The results give that the mixed hemimicells system,formed by 20 mg of Fe₃O₄/SiO₂ NPs and 0.18 mL 0.5 mg/mL CPC under the solution with pH 9,was used to extract and enrich OTA in water samples with 200mL volumes.A good linearity for OTA was obtained in the range from 2.5 to 250ng/L with r of 0.9995.The detection limit was 0.83 ng/L.OTA from well water,lab water,waste water and river water were extracted successfully by the materials and quantified by HPLC.The recoveries were in the range of 90.0-96.7%,RSDs were1.5-3.5%.Compared to the traditional solid-phase extraction,the pretreatment materials have stronger extraction abilities,the maximum adsorption capacity was5.95 mg/g.Additionally,the Fe₃O₄/SiO₂ NPs have satisfied stability with at least six successive cycles,saving experimental cost.2)The magnetic molecularly imprinted polymers?OTA-Fe₃O₄@PDA MIPs?were developed based on self-polymerization of dopamine on the surface of Fe₃O₄NPs with OTA as the template molecular.And OTA from the polymers was eluted by a certain solution.The magnetic molecularly imprinted polymers were characterized by IR and TEM.Based on the cavities with the template molecular matching in spatial structure,OTA,OTB and OTC were recognized and enriched by OTA-Fe₃O₄@PDA MIPs simultaneously.The maximum adsorption capacities were evaluated by Langmuir model with 1.8 mg/g for OTA which is much higher than the national standard limit of China in cereals?5?g/kg?,0.23 mg/g for OTB and 0.17mg/g for OTC.Under the optimized experimental conditions,the good linearities for OTA,OTB and OTC were in the range of 0.01-1 ng/mL,0.02-2 ng/mL and 0.002-0.2ng/mL,respectively.The detection limits were in the range of 1.8-18 pg/mL.The OTA-Fe₃O₄@PDA MIPs can be re-used for at least 7 consecutive adsorption-desorption cycles.3 kinds of ochratoxins were extracted and enriched by the OTA-Fe₃O₄@PDA MIPs in rice and wine samples effectively and determined by HPLC,and the recoveries were 70.0-90.0%.The pretreatment method coupled to HPLC,which the experimental cost is cheaper,will provide theoretical data to draw up the national standard in China with the determination of OTA,OTB and OTC simultaneously.3.Research on Fe₃O₄ molecularly imprinted polymers as adsorption for extraction of aflatoxin B in food samplesFe₃O₄ molecularly imprinted polymers?AFB₁-Fe₃O₄@PDA MIPs?were synthesized by one step through the interactions of?-?bonds and hydrogen bonds between aflatoxin B₁?AFB₁?as template molecular and polydopamine formed via self-polymerization of dopamine in a weak alkaline solution on the surface of Fe₃O₄NPs.The analytical method was developed for extraction and enrichment of AFB₁and AFB₂ in rice,corn,peanut and edible vegetable oil through AFB₁-Fe₃O₄@PDA MIPs as adsorbents,and determination without derivation by ultra high-performance liquid chromatography?UHPLC?with a large flow cell.In this work,the elution solutions for removal of the template molecular and factors affecting extraction efficiencies were studied.The results show that two calibration plots were linear in the range of 2.5-500 pg/mL AFB₁ and 0.5-100 pg/mL AFB₂ with correlation coefficient of the calibration curves of 0.9994 and 0.9995,respectively.The detection limits of AFB₁ and AFB₂ were 0.12 pg/mL and 0.025 pg/mL,respectively,which were lower than these of the national standard method of China.The recoveries were in the range of 83.0-110.0%.The developed method has several advantages,such as simplification,rapid separation for the pretreatment process and quantitative accuracy without derivation,decreasing the error during the whole experiment.