【作者】 林涛；

【导师】 侯贤灯；

【作者基本信息】 四川大学 ， 分析化学， 2023， 博士

【摘要】 原子光谱分析法日益成熟,拓宽传统原子光谱分析技术的应用范围已成为一个重要研究方向。火焰和等离子体是原子光谱分析中重要的原子化器和激发源,基于其实现两种或多种原子光谱信号的同时采集,能够反映相应激发源中更多的物理化学信息,进而通过这种多维光谱信号有望实现新的分析用途。此外,在燃烧学和等离子体分析领域,基于光谱分析技术的高温和等离子体物理参数诊断研究一直备受关注。本论文的主要研究工作围绕火焰和等离子体原子光谱分析技术开展,以火焰或等离子体为原子化器或激发源,结合不同的进样方式构建了多种原子光谱分析检测系统,从理论原理出发结合原子光谱信号的同时采集建立了新的高温测量方法。并成功地将新开发的光谱采集系统应用到高温测量、火焰和等离子体的原子化机理探究以及痕量重金属的检测中。本论文研究工作主要包括以下五个方面:(1)火焰温度测量:双元素原子吸收双线法。为解决传统的原子吸收双线法进行温度测量时吸光度值较小的谱线易受系统误差干扰而影响结果准确性的问题,开发了一种双元素原子吸收双线测温法。通过将火焰原子吸收光谱仪的检测器替换为便携式电荷耦合器件(Charge Coupled Device,CCD)光谱仪并使用双元素空心阴极灯作为辐射光源,构建了双元素原子吸收光谱同时测量系统。以Cu和Fe为温标元素结合双元素原子吸收双线法,实现了空气-乙炔火焰温度的测量,并与传统的铟-原子吸收双线法进行了对比,验证了该测温方法的可行性和准确性。通过控制两种元素的浓度,可以实现两条谱线的吸收信号都达到较强信号值范围,从而有效地减少了吸收信号测量过程中由于系统误差造成的火焰温度测量结果的不准确性。该方法有望成为一种替代传统原子吸收双线法的高温测量方法,且可有效避免传统原子吸收双线法易受干扰的问题。(2)原子吸收-发射光谱同时测量:高温测量和原子化行为探究。为实现火焰温度的准确测量以及更好地表征高温火焰的热力学平衡状态,开发了一种原子吸收-发射光谱同时测量的温度测量方法,并基于商业化的火焰原子化器构建了原子吸收和原子发射光谱同时测量系统,实现了多种火焰温度的测量。与此同时,通过原子吸收和发射光谱的同时测量得到火焰内分析物原子化和激发过程的影响因素,其主要受火焰温度和氧化还原氛围的影响。该同时测量系统和温度测量方法有望被应用于原子化和激发机理探究以及高温诊断测量,且该测温方法相对于传统原子光谱测温法由于综合考虑了基态和激发态原子布居,进而更能反映火焰的热力学状态。(3)氢气增强的氢化物发生-介质阻挡放电-原子吸收光谱分析法:仪器装置、机理探究和分析应用。本工作首先构建了以平板构型介质阻挡放电(Dielectric Barrier Discharge,DBD)为原子化器的小型化原子吸收光谱分析仪器,以Zn、Cd和Hg为范例元素,探究了辅助氢气对DBD原子吸收光谱信号的增强效果,并通过一系列表征技术深入探究了氢气的作用机理。使用电感耦合等离子体质谱和X射线光电子能谱技术对在线原子化过程中沉积在原子化器石英管壁上分析物的含量和化学形态进行了分析,结果表明分析物在原子化过程中发生了氧化反应,而外部引入的氢气能够抑制该反应的进行。通过发射光谱法发现氢气的引入会显著提升DBD微等离子体的激发能力。结果表明由于氢气的引入而形成的还原性氛围和DBD微等离子体激发能力的提升是氢气增强其原子吸收信号的主要原因。此外,基于该系统实现了痕量Cd的测定,显现了该系统的分析应用前景。该方法为后续构建基于微等离子体的小型化原子光谱分析仪器提供了一种新的思路。(4)基于介质阻挡放电原子化器/激发源的原子吸收-发射光谱同时测量法研究。常规的原子光谱法仅采集单一种类的原子光谱信号,而二维或多维光谱信号的采集由于能够同时表征基态和激发态自由原子的布居,因此对原子化器或激发源的原子化与激发机理探究具有重要意义。为此构建了DBD微等离子体为原子化器/激发源的原子吸收和发射光谱同时测量系统。以元素Hg为模型元素,从等离子体的物理特性和原子化与激发过程变化差异性出发,探究了氢化物发生和光化学蒸气发生两种进样方式以及双原子分子气体氮气与氢气对氩和氦两种惰性气体形成的微等离子体的影响。该原子吸收-发射光谱同时测定策略因可同时反映基态和激发态布居,为微等离子体的原子化和激发机理研究提供了新的视野。(5)小型化氢化物发生-介质阻挡放电-原子发射光谱法测定中草药汤剂中痕量汞和铅。为拓宽氢化物发生进样结合介质阻挡放电激发源的应用范围,本工作构建了一种新型的空心电极进样的介质阻挡放电原子发射光谱仪,并实现了中药汤剂中重金属的快速现场分析。结合氢化物发生进样系统实现了中药汤剂中Hg和Pb的含量测定,并进一步探究了进样过程中水蒸气和共生氢气对微等离子体激发能力的影响。在最优实验条件下考察了该方法的分析性能,并通过标准物质及中药汤剂加标样品的分析验证了该方法的准确性和分析应用的可行性。该系统具有装置简单、体积小、能耗低、分析性能优异等优点,在现场分析中具有一定的应用前景。更多还原

【Abstract】 Nowadays,atomic spectrometric techniques are considered to be matured,while broadening their application range has been an important research trend.Flame and plasma are conventional atomizers and excitation sources for atomic spectrometry,and simultaneous acquisition of two or more types of atomic spectral signals can provide more comprehensive physical and chemical information about these excitation sources,and it is expected to realize new analytical applications through the acquisition of multidimensional spectral signals.In addition,the diagnosis of high temperature and plasma physical parameters based on spectral analytical techniques has been the focus in the field of combustion and plasma spectral analysis.The aim of this dissertation mainly focuses on flame and plasma atomic spectral analytical techniques.A variety of atomic spectral analytical systems are constructed by using flame or plasma as the atomizer or excitation source combined with different sampling and spectral detection systems.Based on the theoretical principles and the simultaneous acquisition of atomic spectral signals,novel high-temperature measurement methods are established.The newly developed spectral detection systems are successfully applied to the hightemperature measurement,flame and plasma atomization mechanisms exploration,and the detection of trace heavy metals.This dissertation mainly includes the following five projects:(1)Flame temperature measurement: dual-line atomic absorption spectrometry of two elements.To solve the dilemma that the measurement error of spectral line with the low absorbance will significantly affect the accuracy of the measurement when the traditional two-line atomic absorption method is used for temperature measurement,a novel two-line atomic absorption method based on two thermometric elements was developed.A dual-element atomic absorption signals simultaneous measurement system was constructed by replacing the detector with a portable charge coupled device(CCD)spectrometer and using a dual-element hollow cathode lamp as a radiation source.The temperature of air-acetylene flame was measured with Cu and Fe as the thermometrical elements.The feasibility and accuracy of the proposed method were verified by comparing with the traditional two-line atomic absorption method of In.By controlling the concentration of these two thermometric elements,the absorption signals can reach a strong signal range,thus effectively reducing the inaccuracy of flame temperature measurement results caused by systematic errors in the absorption signal measurement process.This method is expected to be an alternative to the traditional two-line atomic absorption method,and it can effectively avoid the interference problem of the traditional double-line atomic absorption method.(2)Simultaneous measurements of atomic absorption and emission spectra: hightemperature measurement and atomization behavior exploration.To achieve an accurate measurement of flame temperature and better characterize the thermodynamic equilibrium state of high-temperature flame,a temperature measurement method based on simultaneous measurement of atomic absorptionemission spectral signals was developed.A simultaneous measurement system for atomic absorption-emission spectra was constructed based on a commercial flame atomizer and the temperature measurement of various flames was realized.Simultaneous measurement of atomic absorption and emission spectra also reveals that the analytes’ atomization and excitation processes were mainly affected by the flame temperature and redox atmosphere.The simultaneous measurement system and temperature measurement method are expected to be applied for atomization and excitation mechanism exploration and high-temperature diagnosis,and the simultaneous detection method can better reflect the thermodynamic state of flame.(3)Hydrogen enhanced hydride generation-dielectric barrier discharge-atomic absorption spectrometry: Instrument,mechanism exploration and analytical application.In this chapter,a miniaturized atomic absorption spectrometer using planar dielectric barrier discharge(DBD)as the atomizer was constructed,the enhancement effect of auxiliary hydrogen on the signals of argon DBD-AAS was explored with Zn,Cd,and Hg as the model elements,and the mechanism of hydrogen enhancement effect was further studied through a series of characterization techniques.The content and chemical state of the analytes deposited on the quartz tube during the online atomization process were analyzed by inductively coupled plasma-mass spectrometry(ICP-MS)and X-ray photoelectron spectroscopy(XPS).The results showed that oxidizing reaction would occur during the atomization process,and auxiliary hydrogen could inhibit the reaction process.It has been found that hydrogen can significantly improve the excitation capability of DBD microplasma.It is concluded that the main reasons for the enhancement effect of hydrogen are the generation of a reducing atmosphere and the improvement of DBD microplasma excitation capability.In addition,taking Cd as an example,the analytical application prospect of the hydrogen-enhanced DBD atomic absorption spectrometer was further explored.This method provides a new idea for the construction of miniaturized atomic spectrometers based on microplasma.(4)A simultaneous atomic absorption and emission spectrometer with dielectric barrier discharge for atomization and excitation.Conventional atomic spectrometers only collect one type of atomic spectral signal,while simultaneous detection of twodimensional or even multidimensional spectral signals is of great significance for the exploration of atomization and excitation mechanisms of an atomizer or an excitation source because it can simultaneously characterize the population of the ground state and excited state free atoms.To this end,an atomic absorption and emission spectra simultaneous detection system was constructed by sharing one DBD microplasma as the atomization/excitation source.Taking element Hg as the model element,the effects of sampling methods of hydride generation and photochemical vapor generation,as well as diatomic molecular gases nitrogen and hydrogen on the microplasma physical properties and atomization and excitation processes of the microplasmas formed by argon and helium gases were investigated.Because the ground state and excited state population can be characterized simultaneously,the simultaneous detection strategy provides a new horizon for the exploration of microplasma atomization and excitation mechanism.(5)Miniaturized hydride generation-dielectric barrier discharge-optical emission spectrometer for the determination of Hg and Pb in traditional Chinese medicine decoction.In order to broaden the application range of hydride generation coupled with a dielectric barrier discharge excitation source,a novel type dielectric barrier discharge atomic emission spectrometer with a hollow electrode was constructed,and then the in-suit analysis of trace heavy elements in traditional Chinese medicine decoctions was realized.The contents of Hg and Pb in decoctions were detected through a hydride generation sampling system,and the effect of water vapor and cogenerated hydrogen on the microplasma excitation capability was investigated by optical emission spectrometry.The analytical performance of this system was investigated under optimized experimental conditions,and the accuracy and feasibility were verified by analyzing the Certified Reference Materials and spiked decoction samples.Due to the advantages of simple device,small size,low energy consumption,and satisfactory analytical performance,the developed system has promising application in field analysis.更多还原