Laser-Induced Breakdown Spectroscopy Coupled with Multivariate Chemometrics for Variety Discrimination of Soil

Abstract

The aim of this work was to analyze the variety of soil by laser-induced breakdown spectroscopy (LIBS) coupled with chemometrics methods. 6 certified reference materials (CRMs) of soil samples were selected and their LIBS spectra were captured. Characteristic emission lines of main elements were identified based on the LIBS curves and corresponding contents. From the identified emission lines, LIBS spectra in 7 lines with high signal-to-noise ratio (SNR) were chosen for further analysis. Principal component analysis (PCA) was carried out using the LIBS spectra at 7 selected lines and an obvious cluster of 6 soils was observed. Soft independent modeling of class analogy (SIMCA) and least-squares support vector machine (LS-SVM) were introduced to establish discriminant models for classifying the 6 types of soils, and they offered the correct discrimination rates of 90% and 100%, respectively. Receiver operating characteristic (ROC) curve was used to evaluate the performance of models and the results demonstrated that the LS-SVM model was promising. Lastly, 8 types of soils from different places were gathered to conduct the same experiments for verifying the selected 7 emission lines and LS-SVM model. The research revealed that LIBS technology coupled with chemometrics could conduct the variety discrimination of soil.

Discrimination of Grape Seeds Using Laser-Induced Breakdown Spectroscopy in Combination with Region Selection and Supervised Classification Methods

“…These new PCs are orthogonal to each other and are sorted according to the explained variance. Generally, the first few PCs explaining most of the total variance are often used for pattern identification [9,16]. PCA is a useful tool to give an easy visualization of the distribution of samples [17,18].…”

“…As the excited species return to the ground state during de-excitation, the emission lines at characteristic wavelengths are collected by the spectrometer, thus allowing analysis of the elemental composition of the sample [8]. In recent decades, the LIBS technique has become very popular thanks to its rapid analysis, high spatial resolution, and the potential to perform in situ and stand-off analysis [9]. Some attempts have been made to verify the feasibility of the LIBS technique to detect elemental composition and identify specific species of agricultural seeds.…”

Chemometrics in laser‐induced breakdown spectroscopy

“…Furthermore, a joint analysis of PLS‐DA and the SVM model was designed, and with this method, 95% of the validation spectra are correctly classified, while no unclassified spectra were observed. Yu et al introduced SIMCA and LSSVM to establish discriminant models for classifying 6 types of soils, and their performances were evaluated on the basis of the Receiver operating characteristic (ROC) curve. The optimal LSSVM model was applied for discriminating the different types of soils and achieved outstanding discrimination results.…”

Analysis of Salt Mixture Contamination on Insulators via Laser-Induced Breakdown Spectroscopy

“…LIBS has been widely applied as a tool for mineral analysis, archaeology, biomedical analysis, aerospace exploration, etc. [6][7][8]. The basic experimental process involves exciting plasma with a high-energy laser and collecting its characteristic spectral information to obtain the elemental composition and surface condition of the target material.…”