Development of compact emission detection devices for the measurement of environmental pollutants using helium radio-frequency plasma

本研究的目的是利用射频（200- 300 kHz）产生的氦等离子体易于实现小型化和稳定化，从而开发出能够对环境污染物进行高灵敏度和高选择性检测的小型原子发射检测器（AED）。雪崩光电二极管（APD）模块用于光度系统。通过选择合适的干涉滤光片，APD模块探测到了硫的一些典型原子发射（921- 923 nm）。通过优化电极的内径和它们之间的距离，所施加的功率和频率，以及等离子体气体的流速等，实现了pg/秒的灵敏度作为GC检测器。接下来，一个更小的和节能的AED装置配备了同轴双管型微等离子体炬新开发。等离子体能够通过使用AED装置以低于1 W的施加功率和几mL/min的等离子体气体产生。将该装置与气相色谱仪联用，通过优化等离子体气体的流量、放电功率、放电频率等参数，提高了CCD光谱仪对有机磷和硫化合物的检测灵敏度，并研制了一种同轴式微等离子体炬电极管对置的AED装置。硫和磷的检出限分别达到8 pg/sec和12 pg/sec。

The purpose of this study was that the development of compact atomic emission detection (AED) devices capable of performing high-sensitive and high-selective detections for environmental pollutants because we paid attention to the easy generation of miniaturized and stable helium plasma by applying radio-wave (200-300kHz).An AED device with high-sensitivity for some organic sulfur compounds was firstly developed. An avalanche photodiode (APD) module was used for the photometric system. Some typical atomic emissions (921-923nm)from sulfur were detected by the APD module after selecting by a suitable interference filter. The pg/sec sensitivity for sulfur was achieved as a GC detector by optimizing the inner diameter of electrodes and the distance between them, the applied power and frequency, and the flow rate of plasma gas etc.Next, a smaller and power-saving AED device equipped with a coaxial double-tube type micro plasma torch was newly developed. The plasma was capable of being generated by using the AED device with below 1W of applied power and a few mL/min of plasma gas. When the AED device was equipped on a GC system, more highly sensitive detection of organic phosphorus and sulfur compounds was performed with a CCD spectrometer after the optimization of applied power and frequency, and the flow rate of plasma gas.Furthermore, another AED device with a coaxial type micro plasma torch with face-to-face positioned electrode tubes was developed. 8pg/sec for sulfur and 12pg/sec for phosphorus as the detection limit were achieved, respectively.