Determination of boron in aqueous solution using a method combining laser ablation molecular isotopic spectrometry with molecular laser-induced fluorescence and isotopic dilution

Abstract

Laser-induced breakdown spectroscopy (LIBS) has been applied in quantitative and isotopic detection of boron. However, the inhomogeneous distribution and possible loss of substance affect the accuracy of quantitative analysis in aqueous solution when using surface-enhanced LIBS (SENLIBS). In this work, a method combining laser ablation molecular isotopic spectrometry enhanced by molecular laser-induced fluorescence and isotopic dilution (ID-LAMIS-MLIF) was proposed to accurately determine boron in aqueous solution. The mechanism of determination of the isotopic abundance ratio (IAR) from the isotopic fluorescence ratio (IFR) in LAMIS-MLIF was discussed and isotopic analysis of boron was carried out using boron monoxide (BO) spectra. The use of isotopic fluorescence ratio reduced the measurement uncertainty from above 15% to below 10%. The best R² of the isotopic abundance ratio calibration curve of 0.999 was reached. Combined with the theory of isotopic dilution analysis, the measured concentration was 1011.2 μg mL⁻¹ for an actual value of 1000 μg mL⁻¹. For 4 solutions under test, the average relative error was 3.76%. These results were much better than those of conventional LIBS to our best knowledge. This work demonstrates that ID-LAMIS-MLIF can be a powerful and potential tool for precise quantitative analysis of boron in aqueous solution.