【作者】 马良；

【导师】 李培武；

【作者基本信息】 中国农业科学院 ， 农产品质量与食物安全， 2007， 博士

【摘要】 黄曲霉毒素B₁（Aflatoxin B₁，AFB₁）危害极大，广泛存在于各种农产品、食品和饲料中，严重威胁人类和动物的生命安全。世界各国设置极其严格的限量标准，造成技术性贸易壁垒，研究建立高灵敏度的AFB₁检测技术，对实施从农田到餐桌的农产品质量控制管理措施，破解技术壁垒，及时发现和剔出受AFB₁污染的产品，防止AFB₁含量超标的产品进入食物链具有重要意义。本研究根据AFB₁的荧光特性，研究提高AFB₁检测灵敏度的方法：采用激光光源进行激光诱导荧光，建立高灵敏度LIF-HPCE AFB₁检测技术；提出AFB₁配合物的荧光增强效应，研究新型HgCl₂荧光增强剂；建立高灵敏度HPLC柱后HgCl₂衍生AFB₁检测技术；应用HgCl₂的荧光增强效应，建立AFB₁免疫亲和柱净化-荧光快速定量检测技术。主要结论如下：1．采用375nm小功率（20mW）半导体泵浦固体激光器作为新型的激发光源，与HPCE耦合，搭建了AFB₁高灵敏度检测平台，以MECC分离模式对AFB₁检测，大大提高灵敏度。缓冲溶液：50mmol／L NaDC，6mmol／L Na₂8₄O₇，10mmol／LNa₂HPO₄，10％乙腈；λex=375nm，λem=440nm，操作电压15kV，电流104μA，毛细管柱直径75μm，柱长度57 cm，到检测窗口距离50cm。方法精密度RSD＜3％，重复性RSD＜5％，回收率为84.1％-96.1％，R²=0.9988。最低检出质量0.17pg，最低定量限0.56pg，绝对检出量的灵敏度提高了3个数量级，显著高于其他方法。2．通过研究AFB₁与多种金属离子荧光体系荧光值变化情况，确定HgCl₂是一种新型的AFB₁荧光增强剂。室温下Hg（Ⅱ）与AFB₁混匀，反应摩尔比大于1：1时，荧光增强反应体系2min内快速、稳定达到平衡，完成最大增强。比传统的荧光增强剂Br₂水增强程度高2倍以上，大大提高了AFB₁的检测灵敏度；验证了Hg（Ⅱ）离子与AFB₁形成配合物荧光增强效应，发生AFB₁到Hg（Ⅱ）的LMCT跃迁，通过光氧化还原反应，形成稳定的配合产物，使反应物体系中刚性结构加强，共轭体系增加，荧光效率提高，荧光值大大增强。3．采用HgCl₂对AFT特别是AFB₁、AFG₁、AFM₁进行柱后衍生，建立高灵敏度HPLC柱后HgCl₂衍生检测技术。流动相为甲醇—乙腈—水（22：18：60 v：v：v），荧光检测器检测（λex=365nm，λem=440nm），柱温30℃，流动相流速0.8mL／min；柱后衍生试剂流速0.4mL／min，进样量10μL，可以在13min内同时分离检测五种主要的AFT（B₁，B₂，G₁，G₂和M₁）。AFB₁的最低检出限和最低定量限分别达到了0.05μg／kg和0.17μg／kg，最低检出质量为0.5pg，绝对检出量的灵敏度提高超过了2个数量级。重复性RSD为1.81％，低于5％；精密度RSD为4.28％，在5％以下；回收率为84.67-91.10％，RSD＜5％。方法成功分析污染花生，花生酱，花生油，大米，玉米等农产品中的黄曲霉毒素，是检测农产品和食品中黄曲霉毒素可靠有效的方法。4．将HgCl₂荧光增强效应引入AFB₁免疫亲和快速测定技术中，建立了一套快速、准确、简易的IAC前处理技术，用于农产品及食品中AFB₁，大大提高了速测技术的检测灵敏度，最低定量限0.3μg／kg，同收率＞90％，单个样品制备在40min之内，RSD＜3％，R²＞0.99，具有操作简单，速度最快，费用最低，准确度高，检测结果直接读数的特点，对环境及检验人员安全性最高，适于现场和口岸检测。更多还原

【Abstract】 Aflatoxin B₁ （AFB₁） seriously threatened human and animal healthy or life safety. AFB₁ commonly contaminates agricultural commodities, food and animal feedstuffs, which is an important problem all through. Standard of AFB₁ limits and technical barriers to trade （TBT） were set by many countries. TBT led to impeded export of agricultural production and damaged the interests of farmers. Development of high sensitivity test method for AFB₁ determination is important and crucial to break out TBT. Detection technology with high sensitivity must be studied in order to guarantee agro-food quality control and management from farm to table, find out the contaminated production in time and prevent the production contained excess the standard AFB₁ into food chain.Based on the fluorescence characteristic of AFB₁, study on how to improve the sensitivity of detection technology was done. First, laser was introduced into the detection technology to induce fluorescence and laser induced fluorescence （LIF）-high performance capillary electrophoresis （HPCE） was developed with high sensitivity. Besides of laser lamp-house researchment, the new fluorescence enhancer of AFB₁ was researched and its scientific hypothesis of AFB₁ chelation fluorescence enhancement was established and deduced from experiments. The novel post-column derivatization method by high performance liquid chromatography （HPLC） was developed with high sensitivity by applied the new fluorescence enhancer. As fluorescence enhancer, HgCl₂ may be induced into IAC fast test method and improved sensitivity. The main conclusions were as follow.1. Laser diode double-pumped solid laser of 375nm wavelength was studied for a new excitation light source and coupled HPCE to detect AFB₁ in MECC separation mode. The optimized conditions were as follow. Buffer was composed of 50mmol/L NaDC, 6mmol/L Na₂B₄O₇, 10mmol/L Na₂HPO₄, 10% Acetonitrile. Excitation wavelength was at 375nm and detected emission wavelength was at 440nm. The applied voltage was 15kV and the current was 104μA. The capillary （75μm i.d., 57 cm total length, 50 cm length to detector） was chosen. The concentration of AFB₁ in samples was determined by LIF-HPCE. The results showed that repeatability expressed as RSD values was under 5% and intermediate precision expressed as RSD values was under 3%. Recovery was in the range of 84.1-96.1%. The data also fit the line y= 10⁶x + 319847 （R²=0.9988） in the linear range of AFB₁. For sample injection volume being little, the absolute limit of detection （0.17pg） and quantitative limit of AFB₁ （0.56pg） were far lower than other method. The absolute mass detection sensitivity of LIF-HPCE improved three magnitudes relatived to AFB₁ detection method2. Fluorescence spectrums and fluorescence signal changes of fluorescence system were researched and fluorescence enhancement technology chelated by metal ions was introduced into AFB₁ fluorescence detection. The result showed that HgCl₂ solvent could be a new enhancer to AFB₁ being enhanced the fluorescence intensity of AFB₁ rapidly, steadily, intensively in the room temperature. The enhanced condition influenced fluorescence system of AFB₁-Hg （II） was studied. The room temperature was accepted. The fluorescence enhancement reaction could balance and complete basically within the 2min when the molar ratio of Hg （II） and AFB₁ should exceed 1:1. In the same condition, enhanced fluorescence intensity by HgCl₂ was stronger than that of Br₂. The sensitivity of AFB₁ detection was improved by HgCl₂ enhancement. Fluorescence enhancement hypothesis of AFB₁ chelation with HgCl₂ was established and deduced. In the process of AFB₁ fluorescence enhancement, octahedral chelated resultant came into being and light redox reaction in LMCT occured and formed steady chelated products. Steady chelated products could extend rigidity plane or conjugate structure and fluorescence intensity was enhanced greatly by fluorescence efficiency being improved3. A novel post-column derivatization method for simultaneous enhancement of aflatoxin B₁, B₂, G₁, G₂, and M₁ by HPLC was developed. The aqueous solution of Mercuric Chloride was utilized as a new fluorescence enhancer for aflatoxin B₁, G₁, and M₁ in post-column. Full separation of five aflatoxins with fluorescence detector （λax=365nm,λam=440nm） could be achieved in the baseline by the mobile phase composed of methanol-acetonitrile-water （22:18:60 v:v:v） within 13 minutes. The flow rate of flow phase was 0.8mL/min and the flow rate of enhancer was 0.4mL/min. Sample injection was 10μL. The sensitivity was improved by the fluorescence intensity enhancement of HgCl₂. The limit of detection of AFB₁ was 0.05μg/kg and limit of quantitative of AFB₁ was 0.17μg/kg. The absolute mass detection sensitivity improved above two magnitudes relatived to AFB₁ detection method. Repeatability expressed as RSD values was 1.81% and intermediate precision expressed as RSD values was 4.28%. Recovery was in the range of 84.67-91.10%. The new method was proven to be an efficient method with high sensitivity, high accuracy and high repeatability for simultaneous determination of aflatoxins and successfully applied to analyze aflatoxins in contaminated peanut, rice, corn, peanut oil, and peanut butter.4. Fluorescence enhancement of HgCl₂ may be induced into IAC fast test method and sample pretreatment technology was developed for AFB₁ determination accurately, fast, conveniently in agricultural production and food. The limit of quantitative was 0.3μg/kg. The recovery of AFB₁ in spiked samples was above 90%. Repeatability expressed as RSD values was under 3% and R² was 0.99. The test time was shorter than 40min of single sample. The pretreatment process was simple and timesaving for whole process time of single sample being within 40min and the time was shorter when sample amount increased. The fast test method fit for test in spot and port etc with highlighted advantages such as high accuracy, low-cost, simple-manipulation, fast-run, high safety and so on.更多还原