Plasma Image-Calibrated Double-Pulse Laser-Induced Breakdown Spectroscopy for High-Precision Quantification of Light Rare Earth Elements in Geological Matrix
来源：ACS Publications
As critical strategic resources for modern high-tech industries, accurate quantitative analysis of light rare earth elements (LREEs) holds significant importance in resource exploration, new energy materials research, and ecological monitoring. Traditional laser-induced breakdown spectroscopy (LIBS) suffers from matrix effects and spectral interference, posing challenges to achieve high quantitative accuracy in low-concentration LREEs detection in geological matrices. This study proposes a novel double-pulse LIBS (DP-LIBS) spectral calibration method integrating plasma imaging information. DP-LIBS was employed to enhance the spectral intensity of trace elements in natural rock samples. An ICCD camera was used to capture plasma images simultaneously with spectral acquisition. By establishing a correlation between the plasma temperature and image brightness, correction factors were calculated to calibrate the original signals. Quantitative analysis of the calibrated spectra reveals the determination coefficients (R2) for LREEs reached up to 99.86%, the root-mean-square error (RMSE) was as low as 0.10, and the optimal relative standard deviation (RSD) was 0.95% (Pr). After calibration, the limits of detection (LODs) for La, Ce, Pr, Nd, Eu, and Sm were 6.24, 9.56, 4.25, 1.27, 0.57, and 3.58 ppm, respectively. In addition, spike-and-recovery experiments were conducted, and the recovery values of the six LREEs were generally within the range of 92.04 to 119.18%. In summary, this spectral calibration method overcomes the limitations of traditional LIBS in ultraprecise quantitative analysis of trace elements, effectively suppresses matrix effects, and provides a new paradigm for the accurate analysis of LREEs in complex matrices.
In conclusion, these results demonstrate that this method effectively mitigates matrix effects and spectral overlapping interferences in traditional LIBS, showing substantial quantitative advantages, particularly for low-concentration samples (e.g., Eu). However, incorporating plasma temperature calculations yields only a little improvement when analyzing elements with limited spectral lines. This study demonstrates that DP-LIBS integrated with plasma image calibration offers a novel approach for analysis of LREEs in complex geological matrices, holding significant application potential in rare earth resource exploration and field-based rapid detection. For field or real-world sample testing using this method, this method is also plagued by issues such as unstable spectral signals of low-concentration elements and a lack of universality in its analytical algorithms. Future research could optimize the quantitative model by incorporating signal enhancement techniques or machine learning algorithms. This would further improve the signal-to-noise ratio (SNR) of ultralow concentration rare earth elements and enhance the analytical performance of the method.