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

本研究的目的是开发能够对环境污染物进行高灵敏度和高选择性检测的紧凑型原子发射探测（AED）装置，因为我们注意到利用无线电波（200-300kHz）易于产生小型化和稳定的氦等离子体。首次研制了一种对某些有机硫化合物具有高灵敏度的AED装置。光度测量系统采用雪崩光电二极管（APD）模块。选择合适的干扰滤光片后，用APD模块检测了硫中921 ~ 923nm的典型原子发射。通过优化电极内径、电极间距、应用功率和频率、等离子体气体流量等因素，实现了GC检测器对硫的灵敏度达到pg/s。然后，研制了一种更小、更节能的同轴双管微型等离子体炬AED装置。使用AED装置，功率低于1W，等离子体气体浓度为几mL/min，即可产生等离子体。将AED装置安装在气相色谱系统上，优化应用功率、频率和等离子体气流量后，CCD光谱仪对有机磷和硫化合物的检测灵敏度更高。在此基础上，研制了另一种同轴微型等离子体炬的AED装置。硫的检出限为8pg/sec，磷的检出限为12pg/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.