大气压低温等离子体发射光谱检测含磷有毒气体(模拟剂)方法研究

Study on Detecting Method of Toxic Agent Containing Phosphorus(Simulation Agent)by Optical Emission Spectroscopy of Atmospheric Pressure Low-Temperature Plasma

化学气体毒剂杀伤快、易扩散、难处置,一旦使用或泄露将对国家安全和社会稳定造成巨大威胁,因此有必要发展一种可以现场实时检测化学毒害气体的方法。目前,传统气体检测方法主要包括红外吸收光谱、气相色谱/质谱、离子迁移谱和各种气体传感器等,但其便携性、灵敏度、广谱性难以兼得,无法完全满足现场检测需求。基于发射光谱(OES)响应快、灵敏度高、广谱性好、可重复性强的独特优势,提出了一种大气压低温等离子体发射光谱检测技术。分别以纳秒高压脉冲、直流自脉冲和微波作为等离子体激励源,使用毒性较小的甲基膦酸二甲酯(DMMP)作为沙林模拟剂进行发射光谱检测;以乙醇作为环境有机干扰物,对乙醇与DMMP光谱进行了主成分分析;并探究了放电脉冲频率与特征光谱强度的关系。结果表明,三种激励源产生的等离子体都可辨别出DMMP特征光谱:P原子特征谱线波长为213.82和215.09 nm,PO基团谱带波长为253.67和255.6 nm。光谱识别度方面,使用微波激励源时DMMP特征光谱最为明显,而使用纳秒脉冲与直流自脉冲激励源时光谱连续本底强烈。方法适用性方面,微波等离子体无电极污染、但需要氩气维持,可作为建立毒害气体发射光谱数据库的手段;而纳秒脉冲与直流自脉冲激励源可在常压空气环境中直接检测。三种激励形式下等离子体区域都存在气体加热效应,微波等离子体气体温度最高(约1300 K),而纳秒脉冲和直流自脉冲放电气体温度相近(分别约为980和880 K)。研究发现,提升脉冲重复频率可以显著增加DMMP特征光谱强度,其与脉冲频率在1~40 kHz内呈线性关系(相关系数大于0.98)。所提出的大气压等离子体发射光谱检测方法具有响应快、操作简单等优点,可扩展性强、具有小型化潜力,为毒害气体快速检测装备研发提供了技术参考。

Gas chemical agent is fast-killing,highly diffusible,and difficult to decontaminate,threatening national security and social stability if used or leaked.Therefore,it is necessary to develop a gas detection method that can be used in real-time and on-site.Existing gas detection methods include infrared absorption spectroscopy,gas chromatography/mass spectroscopy,ion mobility spectrometry,and different gas sensors.Even so,these methods cannot achieve portability,sensitivity,and broad-spectrum simultaneously and meet the requirement of real-time and on-site detection.Based on the unique advantages of optical emission spectroscopy(OES),such as fast response,high sensitivity,broad-spectrum,and good repeatability,this work proposes a gas detection technology with OES from low-temperature plasma(LTP)at atmospheric pressure.Three excitation sources,i.e.,nanosecond pulse,direct current(DC)self-pulse,and microwave(MW)generate LTP.Dimethyl methylphosphonate(DMMP)is used as the stimulant of sarin,of which OES is obtained.Ethanol is used as the organic interference in the environment.The principal component analysis(PCA)of OES from ethanol and DMMP is carried out.The relationship between pulse repetition rate and OES intensity from DMMP is explored.Results show that three sources can distinguish the characteristic OES from DMMP:the wavelengths of P atom are 213.82 and 215.09 nm,and those of PO radical are 253.67 and 255.6 nm.Regarding spectral discrimination,OES from DMMP in MW plasma is the clearest,while the continuous background is strong when using nanosecond pulse and DC self-pulse.In terms of device applicability,MW plasma,sustained with argon,can avoid electrode contamination and be an effective method to establish an OES database for chemical agents.Nanosecond pulse and DC self-pulse discharges can be directly operated in ambient air.The gas temperature(T_(g))of MW plasma is the highest(about 1300 K),while T_(g) of nanosecond pulse and DC self-pulse is similar(980 K vs 880 K).A linear relationship between OES intensity from DMMP and pulse repetition rate is observed in the range of 1~40 kHz,with correlation coefficients greater than 0.98.The OES detection method proposed in this work has the advantage of fast response and easy operation,and the potential of extensibility and miniaturization.This work verifies the feasibility of OES from LTP for chemical agent detection and provides a technical reference for equipment development in the future.