银饰品中铜杂质含量的激光剥离—激光诱导击穿光谱定量分析

正交双波长双脉冲的激光剥离—激光诱导击穿光谱技术能够在较少样品烧蚀的前提下获得高的光谱分析灵敏度，因此该技术可以从根本上解决在单脉冲激光诱导击穿光谱技术中空间分辨本领与光谱分析灵敏度之间的矛盾。为了消除在该光谱技术中的实验参数对光谱信号强度及其定量分析结果的影响，实验研究了银饰品中杂质铜的光谱信号与银元素的光谱信号的相关性。研究结果表明：324.75 nm的铜原子辐射线与328.07 nm的银原子辐射线的强度呈很高的线性相关性，因此选择以银328.07 nm的光谱线作为内标线，采用内标法就可以消除双光束激光的空间几何配置以及剥离激光脉冲能量等实验参数对铜原子辐射信号的影响，从而可以采用正交双波长双脉冲激光剥离——激光诱导击穿光谱技术开展银饰品中铜杂质含量的定量分析。选择银328.07 nm的光谱线作为内标线，基于内标法建立了铜的校正曲线。当激光烧蚀坑洞直径约为17 μm时, 当前实验条件下银饰品中铜元素的检出限可以达到44 ppm。

Quantitative Analysis of Copper Impurity in Silver Jewellery by Laser-Ablation Laser-Induced Breakdown Spectroscopy

High spectral analysis sensitivity can be achieved with orthogonal dual-wavelength dual-pulse laser-ablation laser-induced breakdown spectroscopy under minimal sample ablation. Therefore, the contradiction between spatial resolution and analytical sensitivity existed in single-pulse laser-induced breakdown spectroscopy can be resolved fundamentally in this technique. In order to eliminate the influence of different experimental parameters to the signal intensities and final results of quantitative analysis, the correlation between copper atomicemission and silver atomic emission was studied experimentally in this technique for silver jewellery samples. It was demonstrated that the intensity of atomicemission of copper at 324.75 nm and that of silver at 328.07 nm was linearly correlated with high correlation coefficient. Therefore, it was possible to eliminate the influence of different experimental parameters, such as geometrical arrangement and pulse energy of the ablation laser to the signal of copper atomic emission by selecting 328.07 nm line of silver as internal standard. A quantitative analysis of copper impurity in silver jewellery can be realized by using orthogonal dual-wavelength dual-pulse laser-ablation laser-induced breakdownspectroscopy. A calibration curve of copper was successfully built based on internal standard method while selecting 328.07 nm line of silver as internal standard. The limit of detection of copper in silver matrix was determined to be 44 ppm in this technique when the crater’s diameter was about 17 μm under currentexperimental condition.