Semi-quantitative analysis of metal alloys, brass and soil samples by calibration-free laser-induced breakdown spectroscopy: recent results and considerations

Abstract

The calibration-free methodology described in the literature dealing with the technique of laser induced breakdown spectroscopy has been applied here to several samples under different operating pressures with the aim of classifying the analytical technique as quantitative, semi-quantitative or qualitative (with quantitative estimates only), depending on the relative percentage errors calculated for the major, minor and trace elemental composition of the sample. The results were obtained with a Q-switched Nd:YAG laser (1064 nm), characterized by 5.3 ns duration pulses at a maximum repetition frequency of 10 Hz and with pulse energy up to 300 mJ. The spectra were taken with a grating monochromator coupled with an intensified CCD detector, calibrated from 220 to 700 nm. The samples investigated were aluminum alloy standard disks, standard reference materials of Zn alloy, Cu-Ni alloy, Ti alloy, Ni alloy powder, Cu-Zn alloy and soils. The data are compared with those published in the literature. The results show that the best accuracy (5% relative error) is usually obtained for the matrix element, while in most cases, for the remainder of the components in the sample (major, minor or trace composition), the results can only be considered semi-quantitative (<200% relative error).

Investigation of local thermodynamic equilibrium of laser induced Al2O3–TiC plasma in argon by spatially resolved optical emission spectroscopy

“…Thiyagarajana and Scharer 17 have shown that the plasma of air is in LTE condition for time less than 2 microseconds. The same conclusion has been found by Herrera et al 18 by studying Al alloy laser induced plasma in air generated by Nd:YAG laser. Barthelemy et al 19 have studied the Al plasma by excimer laser in air, they found some evidence of a departure from LTE for the ionized states, presumably because the plasma cannot be considered stationary for the higher energy states.…”

Calibration-Free Laser-Induced Breakdown Spectroscopy: State of the art

“…It is clear that using an echelle-like instrument as the spectral resolving system allows saving measurement time, because a broadband spectrum is acquired in a single run. However, CF-LIBS analysis of wide range spectra collected by multiple acquisitions of successive spectral windows with a grating monochromator has been also documented with very good results [19]. The crucial points are: the accurate characterization of the instrument spectral efficiency over the whole wavelength range of interest and the stability of plasma (and instrumental) conditions during the measurement.…”

“…Most frequently, the CF-LIBS analysis has been applied to solid materials: aluminum alloys [7,[15][16][17][18][19], steel and iron alloys [15,[18][19][20], precious alloys for jewelry [21,22], copper alloys [19,[23][24][25][26][27][28], archaeological copper artifacts [24,29], glasses [23], pigments on roman frescoes [30] and on parchments [31], soils and rocks [32][33][34], meteorites [35], coral skeletons [36], human hair [37].…”

“…By the way, Sallé et al [33] tested CF-LIBS quantitative analysis on spectra that were acquired in a stand-off configuration at intermediate distance (3 m). In Herrera et al [19], different pressure conditions (1000 mbar, 100 mbar and 0.1 mbar) of an air environment were tested to identify the most favorable experimental conditions (see Section 2.1).…”

Development of a deep-sea laser-induced breakdown spectrometer for in situ multi-element chemical analysis

“…While matrix-matched calibration-curves can be used for quantitative analysis of solids (Hunter and Piper, 2006;Eppler et al, 1996), various groups have successfully implemented CF-LIBS to quantify the composition of metal alloys (Tognoni et al, 2007(Tognoni et al, , 2010Ciucci et al, 1999;Herrera et al, 2009a) and metal oxides (Praher et al, 2010) in a gaseous environment, achieving relative accuracies of 5 to 15% for major elements. With regard to interpretation of natural sediments and rocks, most studies report degradation in accuracy due to the complexity of the signals obtained (Tognoni et al, 2010;Herrera et al, 2009b;Colao et al, 2004;De Giacomo et al, 2007). Moreover, conventional CF methods require all the major elements to be identified in the spectra, which is not possible for the limited range and resolution of the spectrometer used in ChemiCam.…”