【作者】 胡美华；

【导师】 吴芳英； 黄鹏程；

【作者基本信息】 南昌大学 ， 分析化学， 2019， 博士

【摘要】 磁性纳米材料（Magnetic nanoparticles,MNPs）不仅具有比表面积大可提高吸附容量和超顺磁性易于快速分离的特性,而且具有环境友好、制备简单、可多次重复使用等优点。此外,MNPs表面有较多活性基团,可对其表面进行功能化修饰,实现对目标化合物高选择性吸附富集,在样品前处理和分析应用中受到广泛关注。本文以Fe₃O₄纳米材料（Fe₃O₄ nanoparticles,Fe₃O₄ NPs）为核,设计研究了几种核-壳结构的功能化Fe₃O₄ NPs,并结合液相色谱法（High-performance liquid chromatography,HPLC）,构建了用于食品和环境样品中碱性橙类染料、赭曲霉毒素及黄曲霉毒素B的分离富集与定量分析方法。其主要研究结果如下:1、表面功能化Fe₃O₄在食品中碱性橙类染料的应用研究1)以Fe₃O₄ NPs为载体,将阴离子型表面活性剂-十二烷基磺酸钠（Sodium dodecyl sulfonate,SDS）修饰于其表面,制备了十二烷基磺酸钠-Fe₃O₄纳米材料（Fe₃O₄ NPs@SDS）。以此功能化材料为吸附剂,在酸性溶液（pH 4.5）条件下,对腐竹、黄鱼、饮料和葡萄酒等食品中阳离子型染料碱性橙21（Basic orange 21,BO21）和碱性橙22（Basic orange 22,BO22）进行吸附富集,通过外加磁场作用,实现快速分离。随后,以1 mL甲醇解吸,HPLC法定量检测。结果显示,BO21和BO22均在0.02-5μg/mL范围内具有良好的线性关系（相关系数r为0.9999）,最低检出限分别为0.88和0.53μg/kg,加标回收率在72.0-98.0%之间。该前处理方法操作简单、富集效率高（BO21和BO22的最大吸附容量分别为75.8 mg/g和93.5 mg/g）,且整个萃取过程不超过13 min,比国家标准方法（60 min）缩短了4倍多。2)以碱性橙2（Basic orange 2,BO2）为模板分子,利用多巴胺的自聚合作用,在Fe₃O₄ NPs表面形成聚合物层,再选用3%乙酸-20%乙腈混合液（v/v）洗脱模板分子,合成了高选择性识别BO2的磁分子印迹材料（BO2-Fe₃O₄@PDA MIPs）。通过对材料用量、pH、超声时间及解吸液种类和体积等萃取条件的探讨和优化,实现了对腐竹、黄鱼、饮料、辣椒粉和葡萄酒等实际样品中BO2的选择性萃取。结果发现,最佳实验条件为BO2-Fe₃O₄@PDA MIPs用量为15 mg,pH为5.6,超声时间为5 min,解吸液为2（1+1）mL乙醇时,BO2检测浓度范围在0.04-1μg/mL之间,相关系数为0.9991,最低检出限为5.8 ng/mL,实际样品中加标回收率为73.3-90.0%,相对标准偏差在3.1-8.1%之间。另外,该复合材料对BO2的最大吸附容量为24.4 mg/g。该方法简单有效,充分展示了磁分子印迹材料的特异性吸附性能和比表面积大的特点。2、表面功能化Fe₃O₄应用于赭曲霉毒素提取分析研究1)将阳离子型表面活性剂-氯化十六烷基吡啶（Cetylpyridinium chloride,CPC）修饰在Fe₃O₄/SiO₂纳米材料（Fe₃O₄/SiO₂ NPs）表面,形成了混合半胶束磁性吸附材料（Fe₃O₄/SiO₂ NPs@CPC）。基于混合半胶束体系与赭曲霉毒素A（Ochratoxin A,OTA）之间的静电作用和疏水作用,建立了环境水样中OTA的前处理方法,并对影响萃取效率的条件进行了研究和探讨。实验结果阐明,在溶液pH为9时,20 mg Fe₃O₄/SiO₂ NPs与0.18 mL 0.5 mg/mL CPC形成的混合半胶束体系,成功用于200 mL水样中OTA的萃取富集。OTA在2.5-250 ng/L浓度范围内,呈现良好的线性相关性,相关系数为0.9995,最低检出限为0.83ng/L。应用该材料对四种实际水样（井水、实验室水、废水和河水）中OTA进行萃取富集,以HPLC法定量检测,得到回收率在90.0-96.7%范围,相对标准偏差为1.5-3.5%。与传统固相萃取材料相比,该前处理材料富集能力强,对OTA最大吸附容量为5.95 mg/g。同时,实验结果还表明,Fe₃O₄/SiO₂ NPs展示了较好的稳定性,可重复使用6次以上,大大降低使用成本。2)以Fe₃O₄ NPs为核,在多巴胺的自聚合作用下,将模板分子OTA印迹在其表面,再选择适当的洗脱溶液将OTA洗脱下来,制备了专一性较强的磁性分子印迹材料（OTA-Fe₃O₄@PDA MIPs）,并采用IR和TEM技术进行结构表征。利用该材料与模板分子在空间构型上相匹配的空腔,用于OTA、OTB和OTC的同时有效萃取与富集。以Langmuir吸附等温模式评价该磁性分子印迹材料的吸附能力,得出对OTA、OTB和OTC的最大吸附容量分别为1.8、0.23和0.17mg/g,其中对OTA的最大吸附容量远高于我国对谷类中OTA限量要求（5μg/kg）。在最优萃取条件下,OTA、OTB和OTC浓度分别为0.01-1 ng/mL,0.02-2ng/mL和0.002-0.2 ng/mL时,均呈现出良好的线性相关性,最低检出限在1.8-18pg/mL之间。该材料可对3种赭曲霉毒素连续7次重复萃取,结合HPLC法定量分析,获得回收率为70.0-90.0%范围,实现了有效快速对大米和葡萄酒中3种赭曲霉毒素的萃取富集。该方法应用成本低廉,为3种赭曲霉毒素同时测定的国家标准制定提供实验依据。3、Fe₃O₄表面印迹材料在食品中黄曲霉毒素B萃取研究利用多巴胺在弱碱性条件下形成的聚多巴胺,通过π-π键和氢键作用,一步法将模板分子黄曲霉毒素B₁（Aflatoxin B₁,AFB₁）印迹于Fe₃O₄ NPs表面,去除模板分子后,成功制备了高特异性磁性分子印迹材料（AFB₁-Fe₃O₄@PDA MIPs）。再与配有大体积流通池的超高效液相色谱法（Ultra high-performance liquid chromatography,UHPLC）联用,免去黄曲霉毒素B的衍生步骤,构建了磁分子印迹-超高效液相色谱法对大米、玉米、花生和食用油中AFB₁和AFB₂的萃取富集与定量分析。实验对洗脱剂种类进行了研究,并优化了影响萃取效率的因素。实验表明,AFB₁和AFB₂分别在2.5-500 pg/mL和0.5-100 pg/mL浓度范围内,相关系数为0.9994和0.9995,最低检出限为0.12和0.025 pg/mL,均低于国家标准方法的检出限,回收率在83.0-110.0%之间。该方法前处理过程简单,分离速度快,无需衍生化反应可直接定量检测,减少了实验过程中产生的误差。更多还原

【Abstract】 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 0.02-5μg/mL with r of 0.9999.The detection limits were 0.88μg/kg for BO21 and 0.53μg/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 0.04-1μg/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（5μg/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 ofπ-πbonds 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.更多还原