Accuracy improvement of calibration-free laser-induced breakdown spectroscopy

Abstract

Calibration-free laser-induced breakdown spectroscopy can overcome the matrix effect and the huge application prospects of in situ and on-line measurement, so it has been studied and applied to many analytical samples by numerous researchers since it was first proposed in 1999. However, its accuracy is always lower than other analytical techniques and traditional quantitative analysis methods of laser-induced breakdown spectroscopy. The goal of this paper is to review the improvement of accuracy in the experimental setup and spectral analysis, especially after 2010, but not limited to it. The main contents include the accurate measurement of spectral intensity, the spatial and temporal window of local thermodynamic equilibrium and the accurate calculation of temperature and electron density. Due to the requirement of one or more standard samples, the combination of standard samples and CF-LIBS is discussed as a separate section. Finally, a simple conclusion is offered to relevant researchers who want to use CF-LIBS for quantitative analysis.

Comparison of Mg/Ca Concentration Series from Patella Depressa Limpet Shells Using Cf-Libs and La-Icp-Ms

“…5 a Saha-Boltzmann plot for Mg and Ca corresponding to sample LAN.565 is shown). To assess the LTE conditions, the McWhirter criterion has been used [60]. Plasma temperatures obtained from the Saha-Boltzmann plots (see Table 3) are around 7500 K; from this, minimum electronic density to achieve LTE conditions should be 1.8E16 cm − 3 , while our average value is 5.7E16cm − 3 .…”

“…To assure that the emission lines entering the CF-LIBS algorithm are optically thin, a selection procedure has been implemented, following advice in Fu et al [60]. First, an average spectrum from all measurements in each sample is analyzed, and the emission lines are identified.…”

An Improved Sub-Model PLSR Quantitative Analysis Method Based on SVM Classifier for ChemCam Laser-Induced Breakdown Spectroscopy

“…Above all, we assumed that there were four classes, A, B, C and D. Consequently, according to the above formulas for calculating the number of classifiers, a total of six classifiers needed to be trained by the training set. In addition, for each sample of the testing set, we counted the number of votes received by each class (number A, number B, number C, number D) through the following rules (Equations (3)- (8)…”

“…In the traditional analytical chemistry approaches, the observed element emission lines are compared with the persistent lines from the standard database, such as the National Institute of Standards and Technology (NIST) database [8]. Calibration-free (CF)-LIBS is another analysis approach, which compensates for matrix effects through a model without the need for calibration curves produced by standards [9].…”

From big to strong: growth of the Asian laser-induced breakdown spectroscopy community

“…Among all the papers, the work on fundamental LIBS is relatively less prominent as the end user demand for quantitative analysis has pushed the LIBS community to put more focus on the experimental, data processing and applications study. Still, important work on fundamental LIBS such as femtosecond dual-pulse LIBS on the signal enhancement [8], pressure effects on underwater LIBS in ocean environment [9], accuracy improvement on CF-LIBS [10], self-absorption effect at ungated scheme [11] as well as a review on the mechanism and elimination of self-absorption effect [12] was included in this special issue. Several works on the experimental point of view to optimize the LIBS performance were also included, such as a method of laser focusing control in micro LIBS [13], the effect on lens-to-sample distance [14], experimental parameter settings on the matrix effect [15] and experimental factors affecting the limit of detection [16] etc.…”