A method for improving the accuracy of calibration-free laser-induced breakdown spectroscopy by exploiting self-absorption

Simplified LIBS-based intensity-ratio approach for concentration estimation (SLICE): an approach for elemental analysis using laser induced breakdown spectroscopy

We propose what we believe to be a new approach for elemental analysis using laser induced breakdown spectroscopy (LIBS). This method offers enhanced convenience and simplicity for elemental analysis as it eliminates the necessity of Boltzmann/ Saha-Boltzmann plot. It is an intensity-ratio based approach that provides several notable advantages. One of the key benefits is its ability to perform comprehensive elemental analysis using only a few spectral lines; specifically, only n + 1 emission lines are sufficient for a sample containing n elemental species. This offers a great flexibility in the choice of emission lines which do not suffer from self-absorption. Further, high accuracy can be obtained as many repeated estimations from a single measurement are possible. We demonstrate the theory and working procedure of this technique by experimentally recording the data of two samples (binary and ternary copper alloys). A nanosecond Nd:YAG pulsed laser of ∼7 ns pulse duration and 532 nm incident wavelength is used. The results are in good agreement with CF-LIBS and Energy-dispersive X-ray spectroscopy (EDS).

Accurate determination of plasma temperature and electron density using a reference target: one-point calibration LIBS elemental analysis of alloy samples

Elemental analysis of aluminum alloy samples with calibration-free laser-induced breakdown spectroscopy (CF-LIBS) encounters two difficulties: the inconvenience of determining accurate temperature and electron density of the plasma and the influence of self-absorption of the observed aluminum lines. To solve this problem, target-enhanced orthogonal double-pulse laser-induced breakdown spectroscopy in the reheating regime combined with the one-point calibration method was proposed in this work. A mixture of copper powders and K H C O 3 grains was pressed to a pellet and used as the target. Accurate determination of plasma temperature and electron density can be obtained using a reference target. The plasma temperature could be determined with Saha-Boltzmann plot of copper, and the electron density of the plasma could be determined according to the Stark broadening of the H α line of hydrogen. Aluminum alloy samples were analyzed with a relative error of better than 0.02% for a major element. This approach provides a convenient way to determine the temperature and electron density of the plasma more accurately and is able to reduce the influence of self-absorption, which is helpful for realizing quantitative elemental analysis of different samples while using a calibration-free algorithm.

Quantitative elemental analysis of bismuth brass with target-enhanced orthogonal double-pulse LIBS combined with variant one-point calibration

Self-absorption and unknown transition probabilities of the analytical lines hinder the accurate quantitative elemental analysis of bismuth brass with conventional calibration-free laser-induced breakdown spectroscopy (LIBS). In this work, target-enhanced orthogonal double-pulse LIBS combined with a variant one-point calibration method was used to solve this problem and realize quantitative elemental analysis of bismuth brass with a relative error of less than 4%. This approach is able to reduce the influence of self-absorption and capable of using analytical lines with unknown transition probabilities while using a calibration-free algorithm, which is helpful for accurate quantitative elemental analysis of bismuth brass and other samples.

Self-absorption correction method for one-point calibration laser-induced breakdown spectroscopy

As an important variant of calibration-free laser-induced breakdown spectroscopy (CF-LIBS), one-point calibration LIBS (OPC-LIBS) corrects the Boltzmann plot of the unknown sample by using one known sample and obtains higher quantitative accuracy than CF-LIBS. However, the self-absorption effect restricts its accuracy. In this work, a new self-absorption correction (SAC) method for OPC-LIBS is proposed to solve this problem. This method uses an algorithm to correct the self-absorption and does not require the calculation of the self-absorption coefficient. To verify the effectiveness of this SAC method, Ti, V, and Al elements in two titanium alloys were determined by classical OPC-LIBS and OPC-LIBS with SAC. The average relative errors (AREs) of all elements in the two samples were decreased from 8.78% and 9.28% to 8.07% and 7.56%, respectively. The results demonstrated the effectiveness of this SAC method for OPC-LIBS.

Accurate elemental analysis with variant one-point calibration laser-induced breakdown spectroscopy capable of using analytical lines with unknown transition probabilities

Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is a very useful elemental analysis technique. However, it requires knowledge of transition probabilities of the analytical lines. To solve this problem, a variant one-point calibration (OPC) LIBS method was proposed. Quantitative elemental analysis on Cu-Zn-Ag-Au alloys was realized with this method capable of using zinc analytical lines with unknown transition probabilities. The relative error was demonstrated to be less than 3.3%. This variant OPC method will be helpful for quantitative elemental analysis of different samples using CF-LIBS, no matter whether the transition probabilities of the observed lines are known or unknown.

Accuracy improvement of single-sample calibration laser-induced breakdown spectroscopy with self-absorption correction

The single sample calibration laser-induced breakdown spectroscopy (SSC-LIBS) is quite suitable for the fields where the standard sample is hard to obtain, including space exploration, geology, archaeology, and jewelry identification. But in practice, the self-absorption effect of plasma destroys the linear relationship of spectral intensity and element concentration based on the Lomakin-Scherbe formula which is the guarantee of the high accuracy of the SSC-LIBS. Thus, the self-absorption effect limits the quantitative accuracy of SSC-LIBS greatly. In this work, an improved SSC-LIBS with self-absorption correction (SSC-LIBS with SAC) is proposed for the promotion of quantitative accuracy of SSC-LIBS. The SSC-LIBS with SAC can correct the intensity ratio of spectral lines in the calculation of SSC-LIBS through relative self-absorption coefficient K without complicated preparatory information. The alloy samples and pressed ore samples were used to verify the effect of the SSC-LIBS with SAC. Compared with SSC-LIBS, for alloy samples, the average RMSEP and average ARE of SSC-LIBS with SAC decreased from 0.83 wt.% and 13.75% to 0.40 wt.% and 4.06%, respectively. For the pressed ore samples, the average RMSEP and average ARE of SSC-LIBS with SAC decreased from 4.77 wt.% and 90.48% to 2.34 wt.% and 14.60%. The experimental result indicates that SSC-LIBS with SAC has a great improvement of quantitative accuracy and better universality compared with traditional SSC-LIBS, which is a mighty promotion of the wide application of SSC-LIBS.