水体重金属电解液阴极脉冲放电光谱低检出限检测研究

Electrolyte cathode atmospheric pressure glow discharge-atomic emission spectrometry (ELCAD-AES) is a new technique to on-line detect metal elements in aqueous solutions in recent years. It has many notable advantages, such as working at atmospheric pressure, simple injection, small size, low operating costs, and detection multi-metal-elements at the same time. However, this technique operates high detection limit for heavy metal elements, which limits its detection capability. Therefore, in the present project, we intend to carry on atmospheric pressure electrolyte cathode discharge spectroscopy sustained by a pulse power supply: the pulse power supply will be employed to generate plasma in order to improve electron excitation temperature of plasma, which will promote atomization and stimulated efficiency of heavy metal elements, and then enhance the stability of plasma and eliminate the background spectral interference by optimizing electrode structure and gas blowing. The detection limit of ELCAD-AES for heavy metals in aqueous solutions will become lower by these improvements. We will study the effects of high voltage pulsed discharge on the atomic radiation intensities of heavy metals and plasma parameters (such as electron excitation temperature, electron density, etc.), and explore the migration mechanisms of heavy metal ions in solution-plasma interface as well as the recombination and excitation mechanisms in the plasma region, and reveal the basic properties of the electrode cathode discharge plasma, and obtain the methods to improve spectral radiation intensity, signal to noise ratio and detection sensitivity. The research results will provide important experimental references and instrument parameters for developing miniature, low-cost heavy metals online detection equipment in aqueous solutions.

电解液阴极放电光谱是近年来出现的一种在线检测水体金属元素的新方法。该技术具有开放大气环境工作，进样简便，体积小，运行费用低，可同时检测多种金属元素等显著特征。但该方法对重金属元素的检出限偏高，限制了对重金属的检测能力。为此，本项目拟开展脉冲电源维持的大气压电解液阴极放电光谱技术研究：采用高压脉冲电源驱动，提高等离子体的电子激发温度，促进重金属元素的原子化和被激发，结合电极结构优化和气体吹动等措施，增强等离子体稳定性、消除背景光谱干扰，实现水体重金属的低检出限检测。本项目将研究高压脉冲放电对重金属原子辐射和等离子体的电子激发温度、电子密度等参数的影响；探索重金属离子在溶液-等离子体界面上的迁移机理和在等离子体区内的复合激发机理，揭示电解液阴极放电等离子体的基本特性，获得提高光谱辐射强度、信噪比和检测灵敏度的方法。研究结果将为开发微型、低成本的水体重金属在线检测设备提供重要实验依据和仪器参数。

电解液阴极放电光谱是近年来出现的一种在线检测水体金属元素的新方法。它在大气压下工作，不需要复杂的真空系统、气体压力以及温度控制系统；采用待测溶液为放电的一极，直接解决了发射光谱(如ICP-AES)中一直困扰人们的液体样品的进样问题，不需要复杂的进样喷嘴系统。电解液阴极构建简单，极大的简化了发射光谱的光源发生系统，使得发射光谱技术有可能在实验室之外的条件下使用。项目组自行设计、加工并安装调试了电解液阴极辉光放电光谱检测实验装置。在交流脉冲电源和交流调制正脉冲电源的驱动下，产生了稳定的脉冲放电等离子体，实验研究了电极形状和尺寸对的脉冲放电等离子体的影响，获得了稳定放电的电极结构；研究样品流速、电解质种类和浓度等参数以及放电电压、电流和频率对对金属元素发射光谱强度的影响，获得了最佳的光谱探测条件，实现了水体金属离子的痕量检测。在金属电极-电解液平面结构下，首次获得了大气压交流脉冲自组织放电斑图模式，放电可产生单环、双环和等离子体点三种模式，并获得了两种不同结构的等离子体点斑图模式。实验研究了电源频率、电极间距、电源功率和电解质电导率对放电不同模式的影响。提出了电解液阴极辉光放电-脉冲激光激发等离子体光谱技术，实现了对水体中痕量汞元素的检测。在国内外期刊上发表学术论文15篇，申请专利5项，参加国内外学术会议7次，培养研究生10名。