【作者】 杨慧；

【导师】 王富华；

【作者基本信息】 华中农业大学 ， 植物营养学， 2009， 硕士

【摘要】 砷是自然界中常见的元素,也是长期以来被认为对人体健康有负面影响的元素。近年来,随着对砷研究的深入开展,人们发现砷元素的毒性大小是随着化合物的形态不同而变化的,用总量评价砷的毒性和环境污染无法真实反映砷污染状况,因此应该对砷的各种形态进行定性定量分析。本研究选择环境中最常见的毒性较强的四种砷形态(包括As(Ⅲ)、As(Ⅴ)、MMA、DMA)作为分析对象,首次建立了蔬菜中不同形态砷的测定方法。目前,常用的砷形态检测方法包括:高效液相色谱-等离子体质谱法(HPLC-ICP-MS)、氢化物-电感耦合等离子体-原子吸收光谱法(HG-ICP-AAS)、高效液相色谱-氢化物-原子荧光光谱法(HPLC-HG-AFS)。其中,HPLC-HG-AFS具有灵敏度高、价格低廉、稳定性好等优点,是近几年报道最多、应用最广的联用检测方法。本课题优化和建立了HPLC-HG-AFS测定蔬菜中不同形态砷的方法,主要包括以下几个方面:第一,确立研究对象。收集不同种类的蔬菜样品,通过总砷的测定,选择其中砷含量较高的蕨菜作为方法的研究对象。第二,确立仪器条件。包括三个方面:1.分离系统条件的优化。主要考察高效液相色谱分离条件,以磷酸氢二铵作为流动相,在其浓度为15mmol/L、pH为6.0时谱峰得到最好的分离。2.氢化物发生条件的优化。使用盐酸为载流、硼氢化钾为氢化发生还原剂,在盐酸浓度为7%(v/v)、硼氢化钾的浓度为1.5%(w/v)时信噪比达到最佳。3.检测系统条件的优化。主要考察原子荧光检测条件,当光电倍增管负高压为290V、灯电流为100mA、原子化器温度为200℃、载气流速为300ml/min、屏蔽气流速为600ml/min时信噪比达到最佳。第三,前处理方法的选择。以1:1(v/v)甲醇水为提取剂,采用超声(20min)+离心(20min)对蔬菜样品连续提取3次达到最佳效果。第四,方法评价。测定四种形态砷检出限为As(Ⅲ)2μg/L、DMA 4μg/L、MMA 4μg/L、As(Ⅴ)10μg/L,方法平均回收率在82.3%-88.3%之间,相对标准偏差分别为As(Ⅲ)1.01%、DMA2.51%、MMA4.76%、As(Ⅴ)4.67%。四种形态砷表现出良好的线性关系,相关系数均大于0.999。说明方法具有检出限低、准确性好、稳定性高、线性关系显著等特点。本课题的另一部分工作是将优化后的方法应用于蔬菜样品的测定。通过调查市场上常见的陆生蔬菜和水生蔬菜,结果表明:(1)水生蔬菜(海生蔬菜)砷含量普遍高于陆生蔬菜;(2)陆生蔬菜砷含量较低,主要以无机砷形态为主;(3)水生蔬菜(海生蔬菜)砷含量较高,但主要以无毒的有机砷为主,无机砷含量较低:(4)砷富集蔬菜(如蕨菜、污染区油菜等)的砷含量很高,且以毒性最强的无机砷形态存在。更多还原

【Abstract】 Arsenic is one of the ordinary elements in the nature. It has a century-long reputation of being poisonous. Recently, as the development of investigating on arsenic, people know that the toxicity of arsenic is greatly dependent on its chemical form. So the total content of arsenic could not reflect the real influence of it on environment. It is qualitative and quantitative analysis of different arsenic species. Our study selects As（III）、As（V）、MMA、DMA, which have toxicity and universality, as analytical subject to establish speciation method of vegetables for the first time.Now, arsenic speciation analysis is achieved by High Pressure Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry （HPLC-ICP-MS）, Hydride Generation-Inductively Coupled Plasma-Atomic Absorption Spectroscopy （HG-ICP-AAS） and High Pressure Liquid Chromatography-Hydride Generation-Atomic Fluorescence Spectroscopy （HPLC-HG-AFS）. HPLC-HG-AFS is the most reported and the most widely used. It has high accuracy, stability and sensitivity. We want to find a method that used to Arsenic Speciation Analysis of vegetables.Firstly, the object of study is established. We collect different types of vegetable samples and detect the total arsenic content of samples. Bracken is identified as research subjects, because it’s higher arsenic content.Secondly, the equipment condition is optimized. Include three aspects: 1 .Optimization of separation system. The main study is for HPLC separation conditions. The concentration is 15 mmol/L, the pH is 6.0, and （NH₄）₂HPO₄ is used as mobile phase. The four arsenic species are baseline separated. 2. Optimization of HG. Carrier solution is 7 % （v/v） Hcl, reducing agent of HG is 1.5% （m/v） KBH₄ solution. 3. Optimization of detection system. The main study is for AFS detection system. The best conditions include that: the photomultiplier tube of negative high voltage is 290 V, lamp current is 100 mA, atomization temperate is 200℃, carrier gas’s flow rate is 300 ml/min, and shielding gas’s flow rate is 600 ml/min.Thirdly, pre-treatment method is chose. Extract is 1:1 （v/v） methanol-water solution. Ultrasound （20 min） - centrifugal （20 min） through 3 consecutive times extraction is the extraction method.Fourthly, the method is evaluated. Independently, the DL are: As（III） 2μg/L、DMA 4μg/L、MMA 4μg/L、As（ V） 10μg/L, the recovery is between 82.3%-88.3%, and the RSD are: As（III） 1.01%, DMA 2.51%, MMA4.76%, As（V） 4.67%. It shows that the four arsenic species has good linearity, correlation coefficient> 0.999. It indicates that the method has the characteristic of high sensitivity, good accuracy, stability and wide range of linearity.Another part of the study is to make optimized method apply in the vegetables sample determination. Through investigation market in common terrestrial vegetables and aquatic vegetables, finally indicated: （1） The aquatic vegetables arsenic content is higher than the terrestrial vegetables general; （2） The terrestrial vegetables arsenic content is lower and mainly by inorganic arsenic shape primarily; （3） The aquatic vegetables arsenic content is higher, but by the non-toxic organic arsenic primarily, the inorganic arsenic content is mainly low; （4） The Arsenic-rich vegetables （such as bracken, rapes in contaminated areas, etc.） the arsenic content is very high and by toxic strongest inorganic arsenic forms existence.更多还原