基于放电辅助激光诱导击穿光谱技术的水中痕量金属元素检测分析  

Analysis of Trace Metal Elements in Water Based on Discharge-Assisted Laser-Induced Breakdown Spectroscopy

作　　者：许博坪 刘颖华 刘在浩 尹培琪 汤洁[1,2] Xu Boping;Liu Yinghua;Liu Zaihao;Yin Peiqi;Tang Jie(State Key Laboratory of Transient Optics and Photonics Xi'an Institute of Optics and Precision Mechanics of CAS,Xi'an 710119 China;University of Chinese Academy of Sciences,Beijing 100049 China)

机构地区：[1]中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室,西安710119 [2]中国科学院大学,北京100049

出　　处：《电工技术学报》2023年第17期4757-4766,共10页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金(52177166,51877210);陕西省自然科学基金(2020JM-309)资助项目。

摘　　要：有毒金属离子引起的水污染已经成为一个严重的环境问题。激光诱导击穿光谱(LIBS)技术作为一种新型分析技术,可用于检测任何形态的样品。然而,液体中等离子体快速淬灭、液面波动造成的污染,以及激光能量的有限吸收,均导致LIBS技术在探测水体中痕量元素时光谱强度弱、信噪比差、检测灵敏度低。为此,该文提出一种放电辅助LIBS技术(D-LIBS)用于提升LIBS技术在水体中的痕量探测性能。利用中速滤纸对待测溶液进行快速采样。与传统单脉冲LIBS技术(C-LIBS)相比,由于额外电能的注入,D-LIBS极大增强了等离子体的光谱强度。在最优条件下,D-LIBS使Ba离子光谱强度和信噪比分别提升至C-LIBS的30倍和56倍。凭借D-LIBS的显著光谱增强效应,Ba元素检出限降低至0.26mg/L,检测灵敏度提升至C-LIBS的48倍。Heavy metal ion-induced water pollution has become a severe environment in the world.Laser-induced breakdown spectroscopy(LIBS)is a novel analytical technique based on the atomic emission spectroscopy,which can be used for the target in any state.Thus,LIBS is widely applied in various applications,including environmental pollution monitoring,food safety,and chemical engineering production.However,for liquid sample detection, the rapid quenching of the plasma, the contamination of the optical system by the unstable liquid level, and the limited laser energy absorption of the plasma have limited the further development of LIBS technology. Here, a discharge-assisted LIBS technique (D-LIBS) for the detection of trace elements in solutions is proposed and compared with the conventional LIBS (C-LIBS). Rapid sampling of mixed BaCl2 and NaCl2 solutions is performed using medium-speed filter paper. A Nd:YAG laser is implemented to generate plasmas containing the target elements on the filter paper. A discharge assistance consists mainly of a high voltage DC power supply, a capacitor, and a pair of rod electrodes. The capacitor is first charged by the high voltage DC power supply. The electrodes are respectively connected to the positive and negative terminals of the capacitor, and placed horizontally on the surface of the filter paper. Once the sample surface is ablated by the focused laser beam, the pre-existing plasma between the electrodes acts as the seed charged particles in the discharge gap, which rapidly ignites a strong discharge there. Compared to the time-integrated spectra in C-LIBS and D-LIBS, the LIBS signal has been greatly increased by using the discharge assistance. Emission lines of BaⅡ455.40 nm and NaⅠ588.99 nm are respectively enhanced to 30-fold and 6-fold. The spectral intensities in C-LIBS and D-LIBS are positively correlated with laser energy. However, the spectral enhancement factors show higher values at small laser energy conditions, and the BaⅡ spectral enhancement factor decreases from 3

关 键 词：放电辅助激光诱导击穿光谱 滤纸采样 水溶液 痕量金属元素 

分 类 号：O433[机械工程—光学工程] TM89[理学—光学]