【作者】 徐祥书；

【导师】 邓必阳；

【作者基本信息】 广西师范大学 ， 分析化学， 2008， 硕士

【摘要】 牛奶中所含的各种营养元素,与人体营养需求模式最为相似,且易于消化吸收。牛奶是人们日常不可缺少的营养品之一,因此分析牛奶中微量元素非常重要,这不仅因为微量元素可指示环境污染状况,也是有毒金属进入人体的重要途径。电感耦合等离子体光谱(ICP-OES/MS)以其检测限低、精密度高、选择性好、基体效应小、线性范围宽和多元素同时测定等优点得到了广泛的应用。但是随着科学的发展仅靠ICP-OES/MS常规检测已不能满足研究要求,将ICP-OES/MS与其它分析手段联用起来可以在一定程度上将两者优点结合起来,进而提高分析性能,满足分析要求。作为原子光谱/质谱分析中的进样技术之一的氢化物发生法(HG),由于其采用化学反应实现了待测组分与大量基体分离,一方面使其测定可在无基体光谱干扰下进行,另一方面样品以气体的方式引入,进样效率大幅度的提高,大大提高了分析的灵敏度,已成为强有力的分析工具之一。氢化物发生与ICP-OES联用技术扩展了ICP-OES对氢化物形成元素的检测能力,可使氢化物形成元素的检出限改善1~2个数量级,并且几乎消除了干扰,从而开辟了解决复杂基体样品分析新途径。毛细管电泳(CE)具有分离效率高、分析速度快、分析模式多、试剂模式多、试剂用量少、应用范围广、易于自动化等优点,成为复杂体系中成分分析的重要分析方法之一。将CE-ICP-OES联用技术结合了CE分离效能高和ICP-OES具有多元素同时测定和检出限低,线性范围宽等优点,为复杂样品的元素形态分析提供了一种强有力的分析手段。本论文将ICP-OES与氢化物发生和毛细管电泳联用应用于牛奶中有害元素测定、铅烷发生机理和铝形态分析中,论文的主要内容及研究结果如下:1.建立了简单、快速的微波消解-氢化物发生-电感耦合等离子体光发射光谱法同时测定牛奶中的砷、硒、锑和铋。牛奶样品经微波消解、赶酸后,在沸水浴中用6 mol/L盐酸预还原硒40 min,在室温下用盐酸羟胺预还原砷和锑。用酒石酸和柠檬酸消除牛奶样品中共存元素的干扰。砷、硒、锑和铋的检出限分别为0.24μg/L,0.12μg/L,0.06μg/L和0.02μg/L;样品的平均相对标准偏差分别为5.0%、5.7%、4.3%和3.8%。2.为了阐明在Pb(II)-NaBH4-K3Fe(CN)6体系中铅烷发生机理,研究在K3Fe(CN)6参与下Pb(II)和NaBH4反应的中间产物。产生的铅烷用连续流动氢化物发生-电感耦合等离子体光发射光谱法检测。基于实验结果,机理可描述如下:1) Pb(II)和NaBH4反应生成铅烷和黑色单质铅沉淀;2)此黑色铅被K3Fe(CN)6氧化并形成Pb2[Fe(CN)6]络合物,Pb2[Fe(CN)6]进一步与NaBH4反应生成黑色铅和更多的铅烷;3)进行下一轮循环反应,黑色铅不断产生和不断被K3Fe(CN)6氧化形成Pb2[Fe(CN)6]络合物。总之,在Pb(II)-NaBH4-K3Fe(CN)6体系中,黑色单质铅和Pb2[Fe(CN)6]络合物是产生铅烷的关键中间产物。3.把毛细管电泳-电感耦合等离子体光发射光谱联用技术应用于牛奶中铝的形态分析。牛奶中主要有六种形态的铝存在,通过标准铝和柠檬酸铝迁移时间来定位表征牛奶中游离态铝和柠檬酸铝的形态峰,其迁移时间的相对标准偏差小于3%;用峰面积来定量牛奶中柠檬酸铝的含量分别为0.17 mg/L,其相对标准偏差小于5%。采用以上联用技术对牛奶样品中的柠檬酸铝进行加标回收实验,其回收率为96.4%~100.7%,检出限为37μg/L。更多还原

【Abstract】 The various nutrients in milk are the most similar to human nutritional model. The elemental analysis of milk is important because of an indicator of environmental contamination and a significant pathway for toxic metal intake and a source of essential nutrients for humans.Inductively coupled plasma optical emission spectrometry/mass(ICP-OES/MS) is an powerful multi-elements trace analysis technology. It offers extending good advantages in terms of low detection limit, high precision, good selectivity, little matrix effect, wide linear range and simultaneous multi-elements determination, so it is widely used. But the routine determination of ICP-OES/MS couldn’t meet the research demand with scientific development. The hyphenation of ICP-OES/MS with analytical instruments else would combine advantages of them to a certain extent and ulteriorly improves analytical capability.Hydride generation(HG) combined with modern atomic spectrometric detection has become one of the most powerful analytical tools for some elements determination because it has adopted chemical reaction and realized awaiting measuring component separated from a large number of matrix. It makes determination go on in a situation that there is no any basic spectrum interference. HG-ICP-OES enhance detection power of ICP-OES to hydride–forming elements. The detection limits of hydride-forming elements can be improved by one or two orders of magnitude over conventional nebulizer, and nearly elimination interference. Therefore, it provides a new way to solve complex matrix samples analysis.Capillary electrophoresis (CE) has many advantages: high efficiency, quick analysis speed, many analysis modes, little reagent consumption, wide application, easy automation, etc. It become the important components analysis method in a complex system. CE coupled with ICP-OES has the individual advantages of capillary electrophoresis and inductively coupling plasma spectrometry, it realized the combination of efficient separation and element alternative measurement. It was considered as a powerful analytical method.In this paper, the research has been carried on hyphenating of inductively coupled plasma optical emission spectrometry with hydride generation and capillary electrophoresis. The determination for hydride elements, mechanism of plumbane generation and speciation analysis of aluminum have been studied. The main contents and researched results of the paper are as follows:1. A simple and fast analytical method has been developed for the determination of As, Se, Sb and Bi in milk by microwave digestion hydride generation inductively coupled plasma optical emission spectrometry. Milk were firstly pre-reduced with 6 mol/L HCl for 40 min in a boiled water for Se determination after they were digested in microwave oven, and then were driven away acid and pre-reduced by hydroxylamine hydrochloride for determination of As and Sb. Interferences of concomitant elements were eliminated by tartaric acid and citric acid in the samples. The detection limits(3σ) were 0.24, 0.12, 0.06 and 0.02μg/L for As, Se, Sb and Bi, respectively. The average relative standard deviations were 5.0%, 5.7%, 4.3% and 3.8%, respectively.2. To clarify the mechanisms of the generation of plumbane in the Pb(II)-NaBH4-K3Fe(CN)6 system , the intermediates produced through the reaction of lead(II) and NaBH4 in the presence of K3Fe(CN)6 were studied. The plumbane generated was measured by a continuous flow hydride generator-inductively coupled plasma-optical emission spectrometer. Based on the experimental results, the mechanisms can be depicted in the following steps: 1) plumbane and black lead sediment (black Pb) were formed through the reaction of lead(Ⅱ) and NaBH4 ; 2) the black Pb was oxidized by K3Fe(CN)6 to form the Pb2[Fe(CN)6] complex which was then further reacted with NaBH4 to form more plumbane and black Pb; 3) another round started, i.e. the black Pb thus produced continued to be oxidized by K3Fe(CN)6 to form more Pb2[Fe(CN)6] complex to generate more plumbane. In short, the black Pb and the Pb2[Fe(CN)6] complex were the key intermediate products for the generation of plumbane in the Pb(II)-NaBH4-K3Fe(CN)6 system. 3. The speciation of aluminum in milk has been developed by capillary electrophoresis-inductively coupled plasma optical emission spectrometry. The forms of aluminum in milk have six species. The free aluminum and aluminum citrate were identified by spiked the standard of free aluminum and aluminum citrate. The concentration of aluminum citrate quantified by peaks area was 0.17 mg/L in milk. The relative standard deviation of migration time and concentration for aluminum species were less than 3% and 5%, respectively. The recovery and detection limit of aluminum citrate was in the range of 96.4% to 100.7% and 37μg/L, respectively.更多还原