水稻重金属的MA-LIBS快速微区扫描痕量检测方法研究

Heavy metals pollution of paddy has become a common phenomenon in China. Microanalysis is important link for heavy metals in rice research. The rapid and high efficiency microanalysis is a technical problem for the administration of pollution of heavy metals in rice. Laser induced breakdown spectroscopy (LIBS) has been widely used in the detection of heavy metal elements due to its advantages of rapid, high efficiency, low price and simplicity of operator, and unfortunately, also have the bottleneck problem of achieving an adequate balance between spatial resolution and detection sensitivity. For this reason, in this proposal the technology of Microwave Assisted–Laser Induced Breakdown Spectroscopy (MA-LIBS) will be used to enhance the sensitivity of LIBS by controlling effectively excited by microwave for heavy metals of rice. the threshold of electron density is determined by theory of dispersion and experimentation. The enhancement mechanism of MA-LIBS is explored. electron kinetic energy is next changed. Analytical lines of Cd, Cr and Pb are effectively excited by principle of impact excitation. The micro spot focusing system is designed by software according to parameter of laser. The MA-LIBS, micro spot focusing system and high precision mobile platform are used to solve the contradiction of spatial resolution and detection sensitivity. The high spatial resolution and high sensitivity scanning microanalysis are realized. The results will provide a new tool for rapid, scanning and microanalysis in plant in the future.

近年来，稻谷重金属污染现象日趋普遍，对其进行微区分析是开展水稻重金属研究的关键环节。然而目前的微区检测手段过程繁琐、价格昂贵，无法简便地对水稻重金属进行微区检测。激光诱导击穿光谱(LIBS)在微区分析方面具有快速扫描分析且设备价廉易于操作的优点，缺点是检测灵敏度与空间分辨率相矛盾。本项目提出通过微波辅助的激光诱导击穿光谱技术（MA-LIBS）提高检测灵敏度。基于色散关系理论和实验，确定微波耦合等离子体电子密度阈值；通过研究等离子体参数对信号的影响，探索MA-LIBS信号增强机制；调节微波功率，实现重金属Cd、Cr、Pb的分析线有效激发；实现在少量的激光烧蚀量下，提高检测灵敏度。根据激光器的参数设计微斑聚焦系统。MA-LIBS、微斑聚焦系统和高精密移动平台相结合解决灵敏度与空间分辨率的矛盾，实现水稻重金属的高分辨率、高灵敏度的微区扫描检测，本项目的实施能够为植物快速微区扫描分析提供新手段。

重金属和矿质元素对水稻生长具有重要作用，对矿质元素和重金属进行微区分析是开展水稻研究的关键环节。然而目前的微区检测手段过程繁琐、价格昂贵，无法简便地对水稻金属元素进行微区检测。本项目采用共线双脉冲激光诱导击穿光谱技术提高检测灵敏度。.1）设计具有高空间分辨能力的微光斑聚焦系统，能够消除532nm和1064nm色差，实现焦距50mm，最小20微米的检测。.2）通过图像清晰度评价、自动聚焦算法和三维移动平台相结合实现样品自动聚焦功能。实验验证发现：原子谱线的稳定性高于离子谱线；采用自动聚焦系统，光谱强度的相对标准偏差（RSD）从16.7%降低到6.7%；测量精度大幅提高。 .3）改变两束不同激光波长的时序，开展DP-LIBS相对于SP-LIBS光谱信号强度随两脉冲间隔影响的研究。原子谱线最高可以增强15倍，离子线可以增强4.5倍。.4）对水稻根、茎、叶和叶鞘的矿质元素相互作用关系进行分析研究，研究结果表明：Al、Cu、P、Na和Zn元素在根中含量较高，Si和Mg元素在叶鞘中含量较高。在一定的浓度范围，Al、Cu、P、Na和Zn之间存在协同关系；而K和Ca之间存在拮抗作用。研究了K和Na元素在籽粒中微区分布规律，同时还对水稻籽粒中的矿质元素和重金属进行定量分析研究。.本项目的开展为提高LIBS技术的实现水稻金属元素的高分辨率、高灵敏度的微区扫描检测，本项目的实施能够为植物金属元素快速微区扫描分析提供新手段和研究方法，项目资助发表相关论文5篇，撰写专利7项，其中授权发明专利1项。培养在读研究生1名。