【作者】 吴少尉；

【导师】 金泽祥；

【作者基本信息】 中国地质大学 ， 分析化学， 2004， 硕士

【摘要】 火焰原子吸收光谱法是一种操作特别简单,分析速度快,检出限及精密度能很好满足常规分析检测工作的测试手段。由于常规空气—乙炔火焰温度较低,致使某些易形成难熔氧化物的元素和高熔点、高沸点元素的测定灵敏度较低,干扰严重,有些元素甚至很难测定,可测元素约 30 种。掺氧空气—乙炔火焰是在常规空气—乙炔火焰基础上改进发展起来的一种高温火焰,由于外添氧气和乙炔用量较常规空气—乙炔火焰要多得多,火焰温度提升较高,同时可通过调节氧气、乙炔流量大小及其计量比,适当增强火焰的还原性气氛,这均有利于待测元素氧化物在火焰中有效原子化。拓展了常规空气— 乙炔火焰原子吸收光谱法的应用范围。而近年有关掺氧空气—乙炔火焰原子吸收光谱法的基础研究和实际应用的报道仍很少,可测定元素的具体数目及其分析性能指标缺乏足够的数据和克服干扰的相关资料,潜在的用户对这种高温火焰认识不多。为了更好地为掺氧空气—乙炔火焰原子吸收光谱法的普及提供基础理论数据及指导,作者选择了《掺氧空气—乙炔火焰原子吸收光谱法分析性能的研究》作为硕士研究生论文的研究课题。主要研究成果如下: 一、本文采用镓元素双线吸收法测量了掺氧空气—乙炔火焰的温度。选择了低、中、高温的 30 种元素,从仪器的最佳操作测定条件,存在的干扰及消除,增感效应,可达到的特征浓度、检出限、线性范围等方面进行了系统实验研究。得出掺氧空气—乙炔火焰原子吸收光谱法分析性能的结论为: 1,掺氧空气—乙炔火焰是一种温度在 2300—2900K 的范围内可连续变化调节的火焰。当乙炔量增大至常规空气—乙炔火焰所不能达到的富燃情况时,掺入的氧可与火焰中的碳起氧化作用发生放热反应,燃气与助燃气的用量在单位时间内都相对常规空气—乙炔火焰燃烧状态时增加了 2—4 倍,释放热量加大,从而提高了火焰的温度。选择一定的乙炔和氧气流量,就可获得 2300—2900K 范围内的温度,比常规空气—乙炔火焰的温度高出 300K—500K 左右,这正是掺氧空气—乙炔火焰原子吸收光谱法的分析性能明显优于空气—乙炔火焰原子吸收光谱法不能测定较难挥发和原子化的元素的关键所在。 2、掺氧空气—乙炔火焰保持了较好的还原性气氛。分析测定中,控制乙炔、氧气的流量及其计量比,保持火焰富燃状态,可以很容易增加火焰中 C*、C2*、CH*、CO*等活性含碳自由基,可使元素氧化物很好地解离成气态原子, 使易形成难离解化合物的元素分析性能得以改善。<WP=7>3、掺氧空气—乙炔火焰原子吸收光谱法不适宜测定元素及其氧化物的熔点,沸点在2000K 左右,且氧化物离解能小于 5eV 的低温元素。使用掺氧装置,由于吸收光程缩短及电离效应和气体稀释效应影响,分析效果反而变差。 4、 采用掺氧空气—乙炔火焰原子吸收光谱法测定元素及其氧化物的熔、沸点在 2300—2800K,且氧化物离解能在 4.5—6.0eV 间的中温元素灵敏度都相对常规空气—乙炔火焰原子吸收光谱法有所不同程度的提高,分析性能得以改善。 5、 对元素及其氧化物熔、沸点超过 2800K,且氧化物离解能大于 7.0eV 的高温元素,虽然相对常规空气—乙炔火焰原子吸收光谱法, 掺氧空气—乙炔火焰原子吸收光谱法有了较大改善。但由于掺氧空气—乙炔火焰的温度没超过氧化亚氮—乙炔火焰的温度,而富燃状态的还原气氛也不及氧化亚氮—乙炔火焰强, 测定灵敏度仍不够理想。很难用于实际样品的分析。 二、同时作者也研究了掺氧空气—乙炔火焰原子吸收光谱法测定若干高温元素的实用分析方法,均已公开发表或被录用待刊。 1,掺氧空气–乙炔火焰原子吸收光谱法测定地质样品中的钒。 2,掺氧空气–乙炔火焰原子吸收光谱法测定地质样品中的钛. 3,掺氧空气–乙炔火焰原子吸收光谱法测定地质样品中的痕量铍 光谱学与光谱分析待刊 4,掺氧空气–乙炔火焰原子吸收光谱法测定钢样品中的硅 分析科学学报待刊 最后作者指出,掺氧空气—乙炔火焰原子吸收光谱法在微量进样、悬浮液进样等进样方式,流动注射在线分离富集,以及与色谱联用作元素形态分析等方面,还应有待进一步深入探讨研究。更多还原

【Abstract】 Flame Atomic Absorption Spectrometry (FAAS)is a simple and efficient testingtechnology with good detect limit and precision for daily analysis task. Theconventional air-acetylene FAAS is hard to determine the elements with high meltingpoint and boiling point. The oxygen doped air-acetylene flame is a new type of hightemperature flame. It is developed from the basis of air-acetylene flame. Becauseoxygen is doped and the amount of burning acetylene increased, the temperature offlame is raised. Simultaneously, adjusting the flow proportion of oxygen to acetylenecan enhance the reducing atmosphere of flame. That is all benefit for atomization ofoxide. But the reports for principium research and practical application ofO2-air-C2H2 FAAS is scarce recently, enough data of element determined number andtheir levers of analysis capability are absent, Relative document of excludingdisturbance are infrequent too. Potential users are not familiar with O2-air-C2H2FAAS. I selected the study on analysis capability of O2-air-C2H2 FAAS as my masterdissertation in order to provide principium data and better guide for popularity of it. This paper described two lines absorption way of Gallium to determine thetemperature of O2-air-C2H2 flame and investigated systematically 30 elements withlow, middle, high melting point and boiling point from these aspect:Optimumconditions, the interference effect of coexisting elements, enhancing effect,characteristic concentration, detect limit, linear range. Many conclusions weredrawn. 1. O2-air-C2H2 flame temperature can be adjusted between 2300-2900K by control the flow rate of O2 and C2H2. Doped oxygen can react with surplus acetylene in fuel enriched flame and release heat. So the flame temperature is raised. After the flow rate of oxygen and acetylene are chosen, the relative high temperature can be obtained between 2300 and 2900K. The temperature is 300-500K higher than conventional air-acetylene flame. That is the key reason which O2-air-C2H2 FAAS excel air-C2H2 FAAS for determining the elements of middle temperature of melting and boiling. 2. O2-air-C2H2 flame is a better reducing atmosphere flame than air-C2H2 flame. The amount of free group C*、C2*、CH*、CO*are added by controlling the flow proportion of oxygen and acetylene 3. O2-air-C2H2 FAAS is not suitable for determining the elements whose melting point and boiling point are about 2000K and separation energies of their oxide are not more than 5.0eV. Using apparatus of oxygen doped, the absorption<WP=9>light length is contracted and perhaps there are ionization and dilute effect, the analytical performance get worse4. Those elements whose temperature of melting and boiling lie in 2300— 2800K and separation energies of their oxide lie in 4.5— 6.0eV can be better determined with O2-air-C2H2 FAAS than conventional air-C2H2 FAAS. Because flame temperature and reduction atmosphere are raised.5. Those elements whose melting point and boiling point exceed 2800K and separation energies of their oxide surpass 7.0eV can also be determined with O2-air-C2H2 FAAS. but the temperature addition is limited. The determination sensitivities are not still ideal. It is hardly applied to determining real samplesMoreover, many new methods for determination of trace vanadium、titanium、beryllium in geological samples and trace silicon in steel samples are developedin this paper. Lastly, the development prospect of O2-air-C2H2 atomic absorptionspectrometry is anticipated.更多还原