【作者】 丁兰；

【导师】 金钦汉；

【作者基本信息】 吉林大学 ， 分析化学， 2000， 博士

【摘要】 制约ICP-AES检出限改善的一个最重要因素是样品的引入技术。通常,在ICP-AES中经常使用的样品引入系统为气动雾化系统,包括气动雾化器和雾室。在此系统中待测物传输至等离子体中的效率仅为1%-3%。实验证明热雾化器雾化效率高,是一种更有效的样品引入技术。因此使用热雾化器可以获得更高的信号发射强度和更低的检出限。但是传统热雾化器不适合用于酸性介质、含盐量较高以及悬浆样品。最近,有人提出了一种使用微波来加热强酸性样品溶液的新型热雾化器。该雾化器具有许多传统热雾化器的优点,同时克服了它的一些缺点。但该微波热雾化器所需微波功率较高（300W）,所用聚焦微波炉体积也大,不利于与HPLC连用。本研究则最先提出了一种新型的采用TM₀₁₀谐振腔的低功率微波热雾化器（MWTN）并对其性能进行了较详细和系统的考察。 本研究所设计的低功率微波热雾化器由一段长300mm左右,内径0.5mm,外径1.3mm聚四氟乙烯毛细管缠绕成长约25mm的绕管,该绕管的一端与蠕动泵相连接,另一端固定一小段内径更小的石英或玻璃毛细管（长度小于15mm,内径小于0.15mm）。将该绕管放置于TM₀₁₀谐振腔中心处,酸性样品溶液在该处被加热,雾在毛细管出口处产生。由于在该雾化器中,仅仅在毛细管出口处内径减小,因此在聚四氟乙烯毛细管内的压力低于常规热雾化器毛细管内的压力,因而可以用ICP光谱仪上所使用的蠕动泵来输送样品溶液,而不需要常规热雾化器中所必须的高压泵。产生的雾被送入到加热雾室中,经过水冷凝器冷凝后,干气溶胶被引入到等离子体中。 该雾化器的优点是,用微波谐振腔(TM₀₁₀)作为加热源。由于谐振腔的加热效率好于聚焦微波炉,因此雾化时所需的加热功率大大降更多还原

【Abstract】 One of the major barriers to achieving improved detection limits in inductively coupled plasma atomic emission spectroscopy (ICP-AES) arises from limitations inherent in traditional sample introduction techniques. A typical combination of a pneumatic nebulizer (PN) and spray chamber used for ICP-AES results in analyte transport efficiencies to the plasma in the range of 1 to 2%. Thermospray nebulization (TN) has been demonstrated to be a good means for aerosol generation and of better sample transport efficiency. This increase in efficiency leads to higher signals and improved DLs. Nevertheless, the traditional TN is not well suited to working with acidic or high salt content solutions and slurries. Recently, a new thermospray nebulizer based on the absorption of microwave radiation (MWTN) by aqueous solutions of strong acids was presented. This type of nebulization features many of the advantages of the conventional TN and overcomes some of its drawbacks. In this thesis a novel low-powered microwave thermospray nebulizer for liquid sample introdution into ICP-AES was put forward and its analytical performance was evaluated.In this newly developed system, a microwave resonance cavity (TM010 cavity) was used as the microwave coupling device. Because the efficiency of the resonance cavity was better than that of a focused microwave oven. The power needed to generate the spray was much reduced. A forward power of about 60 W was enough to generate very fine aerosols. Moreover, the system size was reduced, which made it easy to be coupled with a spectrometer.The low MWTN used consists of a knotted PTFE capillary (i.d., 0.5 mm; o.d., 1.3 mm; about 300 mm long) and a short narrow quartz capillary (about 15 mm long; i.d., shorter than 0.15 mm), which was fixed at the outlet of the PTFE capillary by means of a PTFE union. The small narrower quartz capillary is called the outlet capillary. The knotted PTFE capillarywas placed in the central hole of the cavity, where the sample solution was heated and a thermospary took place at the end of the quartz outlet capillary. Because only the outlet capillary is narrow, the pressure inside PTFE capillary is not as high as traditional TN system. Therefore, a peristaltic pump, which was a component of the ICP spectrometer, was enough to push the sample. No high pressure pump was needed. The aerosols produced then entered into the heated spray chamber. After being condensed by a condenser with tap water, the dry aerosols were introduced into the plasma. The low powered microwave thermospray system was coupled with an ICP-AES. The influence of several experimental variables, such as microwave forward powered, acid nature and acid concentration in solutions, sample uptake rate, carrier gas flow rate, the irradiated capillary length in the central hole of the cavity, outlet capillary inner diameter, the temperature of desolvation system and so on, on the emission intensity of elements was evaluated and selected. Under selected optimized conditions, the nebulized efficiency, memory effect, long-term and short-term stability, the DLs and analytical linearity ranges for the studied elements of the low-powered MWTN were studied. In addition, the analytical performance of three sample introduction systems, a low-microwave-powered thermospray nebulizer, a cross-flow pneumatic nebulizer and concentric nebulizer coupled to the same inductively coupled plasma atomic emission spectrometer, was compared. Several parameters including the RF power, the sample uptake rate, the carrier gas flow rate and the observation height(above the load coil) were optimized and compared. Under optimized conditions, the background equivalent concentration of Mn257.610 nm, memory effect, HC1 concentration effect on emission intensity of some selected elements, detection limits(DLs) and relative standard deviation(RSD) for Cd, Co, Cr, Mn, La with these nebulizers were compared. The DLs obtained with MWTN are lower than those with PN, but the RSDs are worse with MWTN than with PN.更多还原