土壤-果蔬中重金属元素的微型液体阴极辉光放电光谱信号增强机理与高精度检测研究

Miniaturization of excitation source is a key technology for developing miniaturized emission spectrometer system. Recently, the electrolyte cathode discharge (ELCAD) has provided a direction for miniaturization of excitation source due to its more compact and portable instrument, lower power consumption, no inert gas requirement. In this project, to meet the trend of miniaturization in analytical instrument and the requirement of on-line detection in field for accidental heavy metal pollution events, a novel miniaturized liquid cathode glow discharge-atomic emission spectrometry (LCGD-AES) is constructed as a rapid and on-line analysis system based on the principle of original ELCAD and characteristic of point discharge. Using the proposed analysis system, we will investigate how to improve the precision and speed of analysis, explore the effect of all kinds of experimental conditions (discharge power, solution pH, solution flow rate, supporting electrolyte, organic reagent as matrix modifier, interfering substance, etc) on the emission intensity and plasma stability, and determine the optimal experimental conditions. Then, the signal enhancement mechanism of organic reagent as matrix modifier is clarified by the transient evolution image of ICCD and spectrum data. Using this technique, we will detect the heavy metals in soil, vegetable and fruit from wastewater-irrigated areas in Baiyin, Gansu province, by using the external standard method, internal standard method and standard addition method. The determination results above three methods will be compared with the values measured by inductively coupled plasma (ICP). Finally, we will determine the optimal method for suitable detection of heavy metals in complex samples by LCGD-AES. This project is of great value to develop miniaturized ELCAD-AES instrument and improve analytical precision. The corresponding result of signal enhancement mechanism is helpful to enrich the interaction theory between plasma and solution.

发射光谱仪的微型化关键是激发源的微型化，而电解液阴极放电(ELCAD)由于具有体积小、能耗低、无气体消耗等优点，为激发源的微型化提供了方向。本项目针对分析仪器的微型化趋势和重金属污染突发事件的现场检测需求，基于ELCAD的原理和尖端放电的特点，通过改进激发源，建立一种新型的微型液体阴极辉光放电原子发射光谱(LCGD-AES)在线快速检测系统。利用该系统，研究提高光谱分析精度和速度的方法，探索各种实验条件对谱线强度和放电稳定性的影响规律，确定元素分析的最优实验条件。通过ICCD相机拍摄的瞬态图像结合光谱数据，阐明有机增敏剂的光谱信号增强机理。用外标法、内标法、标准加入法分析甘肃白银地区土壤-果蔬中的重金属元素，并与ICP测量值比对研究提高测量精度的最优方法。本项目的实施，对研发微型ELCAD-AES仪器和提高分析精度有重要的价值，相关信号增强机理研究有助于丰富等离子体与溶液的相互作用理论。