【作者】 朱振利；

【导师】 张新荣；

【作者基本信息】 清华大学 ， 化学， 2009， 博士

【摘要】 分析系统的小型化是分析化学的一个重要研究方向。微等离子体因为具有体积小、能耗低、气体损耗小、制造费用低廉等优点引起了广泛关注。在本博士论文中,提出了利用微等离子体来建立新型的原子化与离子化方法。本论文主要的研究内容如下:1.提出了基于介质阻挡放电微等离子体的新型氢化物原子化器。与常规的AAS电热石英管原子化器高温下原子化不同,该原子化器能够在低温、低功率消耗下实现氢化物的原子化。另外该原子化器还具有体积小、易于制作、对水蒸气耐受力强的优点。它不仅仅能够实现砷化氢的原子化,还能将有机砷氢化物原子化,可以与HPLC联用实现砷的形态分析。在此实验的基础上,我们还发展了适用于AFS的低温原子化器并应用于As、Se、Pb等元素的分析。2.研究了微等离子体在原子发射光谱中的应用。利用液体阴极放电微等离子体建立了一种新型的汞蒸汽发生技术。该方法不需要任何还原剂,液体中溶解的汞就能够直接被还原为Hg蒸汽,进而用ICP-AES进行检测。该方法具有很高的蒸汽发生效率,还原过程也是瞬时发生的,而且它能够不需要预先将有机汞转化为无机汞,实现有机汞的直接蒸汽发生。此外,我们建立了基于介质阻挡放电的微等离子体发射源,并应用于汞的原子发射光谱检测。该微等离子体对水蒸气有很好的耐受能力,可以不去除水蒸气对冷蒸汽发生引入的Hg激发进行检测。该发射源体积小、功耗低,而且Hg发射线附近的发射背景低且无其它谱线干扰,可以仅仅借助滤光片而不需要其他的分光系统对Hg实现检测。3.建立了一种新型的基于微等离子体射流的大气压解吸附离子源。该离子源通过毛细管内产生的DBD等离子体射流对样品表面的物质进行离子化。它可以对许多常见的有机物(包括极性的和非极性)实现离子化而进行质谱检测。利用该解吸附离子源,我们对药片中的有效组分实现了直接分析,而且还对香烟中的尼古丁、大蒜中的蒜氨酸、以及咖啡豆中的咖啡因实现了直接测定。我们还实现了滤纸表面农药的直接检测。由于该方法不需要复杂的样品处理,不需要溶剂,是一种非常有前景的大气压离子化技术。更多还原

【Abstract】 The development of miniaturized chemical analysis systems is an important trend in analytical chemistry. Recently, microplasmas have attracted attention as potential detection devices for microfluidic systems because of their small size, reduced gas and power consumption, and relatively low manufacturing cost. In the present dissertation, microplasmas have been investigated to develop new atomization and ionization methods. The main contents of the present dissertation are as follows:1. A novel hydride atomizer for AAS based on atmospheric pressure dielectric barrier discharge (DBD) microplasma has been developed. This atomizer offers the advantages of low operation temperature and low power consumption in comparison with the currently used electrothermal quartz atomization operated at 900 0C with a power supply of several hundred watts. The present technique has additional advantages: small size, easiness for fabrication, and good tolerance to residue moisture. Moreover, results indicated that DBD could be used not only for the atomization of arsine, but also for the atomization of hydrides of MMA and DMA. Thus it was coupled to HPLC for the speciation of arsenic. This atomizer was also extended to the atomization of other volatile elements (Sb, Se, and Sn). Based on this study, a low temperature atomizer for AFS has also been developed and applied for the analysis of As, Se, Pb, and Sb.2. New method for mercury analysis based on microplasma sources has been developed for atomic emission spectrometry. First, a new vapor-generation technique is reported for mercury determination in aqueous solutions. Without need for a chemical reducing agent, dissolved mercury species are converted to volatile Hg vapor using a solution cathode glow discharge. In addition, it is applicable to both inorganic and organic Hg determination and has high generation efficiency. Second, microplasma emission source based on DBD has been developed for the determination of Hg. It offers several important advantages over other emission sources: low power consumption (<1W), small size and ease of fabrication, low gas consumption. The DBD microplasma has a relatively modest gas temperature (N2+ rotational temperature of 578±92K) and low continuum and structured background emission. This simple spectral background suggests that Hg emission could be detected effectively with a simple interference filter. The DBD microplasma is also tolerant of residual water vapor within the sample gas stream, making it attractive for use with cold vapor generation sample introduction. Further, the small plasma dimensions, in-line flow cell style, and high plasma stability make the DBD attractive for use with flow injection strategies. These studies suggest that a portable, miniature, automated atomic emission spectrometer based on the DBD would be attractive for the determination of mercury in the field.3. A novel plasma-based desorption/ionization method that can yield mass spectral information under ambient conditions from a range of surfaces without the requirement for sample preparation or additives is reported. The source is carried out by generating a nonthermal DBD plasma jet which interacts directly with the surface of the analyte. Desorption and ionization then occurs at the surface, and ions are sampled by the mass spectrometer. The technique is demonstrated for the detection of active ingredients in pharmaceutical formulations. It has also been successfully applied to the analysis of nicotine in cigarette, thiosulfates in garlic and caffeine in coffee beans. Moreover, it can be applied to the direct analysis of pesticides on the surface. Without the need for prior sample preparation, solvents, it is a promising technique for high-throughput screening in pharmaceutical or food safety analysis.更多还原