关键词: 硼同位素, BO₂ 分子光谱, 微波等离子体炬, 偏最小二乘回归

Abstract: To meet the demand for rapid analysis of boron isotope ratios in solution systems, this study established a Microwave Plasma Torch Molecular Isotopic Spectrometry (MPT-MIS) method for the quantitative determination of boron isotope ratios in solutions. The method employs a microwave plasma torch (MPT) to excite the emission spectrum of BO2 molecules and combines partial least squares regression (PLSR) to extract boron isotopic abundance information from full-spectral shape information, enabling rapid measurement of boron isotope ratios. The memory effect of boron was effectively reduced by using a quartz inner tube, and the spectral preprocessing methods as well as the wavelength range were systematically optimized based on leave-one-out cross validation (LOOCV). Under the optimal preprocessing combination (first derivative + area normalization + 25-point smoothing) and the optimal wavelength range (464–589 nm), only two latent variables (LVs) were needed to sufficiently extract the spectral information related to isotope abundance. On the three samples in the validation set, the maximum relative bias of the model-predicted 11B/10B ratio was 2.04%, and the prediction precision was 1–2% (2σ). Furthermore, it was found experimentally that the BO2 molecular spectral intensity exhibited a good linear relationship with total boron concentration in the range of 5–3000 μg·mL?1 (R2 > 0.999), indicating the potential of this method for simultaneous determination of total boron concentration. This provides a simple and low-cost new approach for the online simultaneous analysis of boron isotope ratios and total boron concentration in scenarios such as the nuclear industry.

Key words: Boron isotope, BO₂ molecular spectroscopy, Microwave plasma torch, Partial least squares regression