College of Instrumentation & Electrical Engineering, Jilin University, Changchun 130061, China.
Anal Methods. 2021 Mar 28;13(12):1502-1510. doi: 10.1039/d1ay00237f. Epub 2021 Mar 10.
Laser-induced breakdown spectroscopy (LIBS) is a rapid, no-sample preparation, remote detection method that has been applied widely in the area of heavy metal detection in the soil. However, the promotion of LIBS is limited by its disadvantages, such as low precision analysis, a high detection limit, and so on. In recent years, many studies have been conducted to improve the LIBS spectral intensity. The double-pulse LIBS (DP-LIBS) is a representative technology in this area. Most of the research work focuses on the analytical methods of DP-LIBS, including the spatial configuration, the inter-pulse time, and the effect of signal enhancement of the DP-LIBS. However, there are few reports about the effect of the energy proportion of the two lasers and the contribution of different laser energies on the signal enhancement, and the inter-pulse time under the conditions of different laser energies. Moreover, DP-LIBS is mostly evaluated by the enhancement factor of the spectral signal, and there are few reports on the quantitative analysis of double-pulse LIBS. This study, which mainly detects Cu, Ni, and Pb in the soil, focuses on the contribution of the signal enhancement by adjusting the energy ratio of the two lasers and the best inter-pulse time under the conditions of different laser energies. Then, quantitative analysis of spectral signals obtained by single-pulse LIBS (SP-LIBS) and DP-LIBS are performed based on the random forest (RF) model. The results demonstrate that DP-LIBS shows better analytical performance than SP-LIBS, the coefficients of determination (R) of the test have great improvement, the root-mean-squared error (RMSE) is much decreased and the relative error is much improved. Thus, this study shows that DP-LIBS is an effective method for the quantitative analysis of heavy metals in the soil.
激光诱导击穿光谱（LIBS）是一种快速、无需样品制备、远程检测方法，已广泛应用于土壤中重金属检测领域。然而，LIBS 的推广受到其缺点的限制，例如低精度分析、高检测限等。近年来，许多研究致力于提高 LIBS 光谱强度。双脉冲 LIBS（DP-LIBS）是该领域的代表性技术。大多数研究工作集中在 DP-LIBS 的分析方法上，包括 DP-LIBS 的空间配置、脉冲间时间以及信号增强的效果。然而，关于双激光能量比例以及不同激光能量对信号增强的贡献和脉冲间时间的研究较少，而且 DP-LIBS 主要通过光谱信号的增强因子进行评估，关于双脉冲 LIBS 的定量分析的报道较少。本研究主要检测土壤中的 Cu、Ni 和 Pb，重点研究通过调整双激光的能量比以及不同激光能量条件下的最佳脉冲间时间来增强信号。然后，基于随机森林（RF）模型对单脉冲 LIBS（SP-LIBS）和 DP-LIBS 获得的光谱信号进行定量分析。结果表明，DP-LIBS 比 SP-LIBS 具有更好的分析性能，测试的决定系数（R）有很大提高，均方根误差（RMSE）大大降低，相对误差大大提高。因此，本研究表明 DP-LIBS 是一种有效的土壤重金属定量分析方法。
