Matrix effect suppressing in the element analysis of soils by laser-induced breakdown spectroscopy with acoustic correction

Laser-induced breakdown spectroscopy (LIBS) has been used for soil analysis, but its measurement accuracy is often influenced by matrix effects of different kinds of soils. In this work, a method for matrix effect suppressing was developed using laser-induced plasma acoustic signals to correct the original spectrum, thereby improving the analysis accuracy of the soil elements. A good linear relationship was investigated firstly between the original spectral intensity and the acoustic signals. The relative standard deviations (RSDs) of Mg, Ca, Sr, and Ba elements were then calculated for both the original spectrum and the spectrum with the acoustic correction, and the RSDs were significantly reduced with the acoustic correction. Finally, calibration curves of Mg I 285.213 nm, Ca I 422.673 nm, Sr I 460.733 nm and Ba II 455.403 nm were established to assess the analytical performance of the proposed acoustic correction method. The values of the determination coefficient (R²) of the calibration curves for Mg, Ca, Sr, and Ba elements, corrected by the acoustic amplitude, are improved from 0.9845, 0.9588, 0.6165, and 0.6490 to 0.9876, 0.9677, 0.8768, and 0.8209, respectively. The values of R² of the calibration curves corrected by the acoustic energy are further improved to 0.9917, 0.9827, 0.8835, and 0.8694, respectively. These results suggest that the matrix effect of LIBS on soils can be clearly improved by using acoustic correction, and acoustic energy correction works more efficiently than acoustic amplitude correction. This work provides a simple and efficient method for correcting matrix effects in the element analysis of soils by acoustic signals.