E. Tognoni

Quantitative micro-analysis by laser-induced breakdown spectroscopy: a review of the experimental approaches☆

Abstract The laser-induced breakdown spectroscopy (LIBS) technique has shown in recent years its great potential for rapid qualitative analysis of materials. Because of the lack of pre-treatment of the material, as well as the speed of analysis, not mentioning the possibility of in situ analysis, this technique offers an attractive solution for a wide range of industrial applications. As a consequence, a lot of work has been devoted towards the application of LIBS technique for quantitative micro-analysis. The purpose of this paper is to give a review of the current experimental approaches used for obtaining quantitative micro-analysis using the LIBS technique. The influence on LIBS analytical performances of laser power, wavelength and pulse length, the proper choice of experimental geometry, the importance of ambient gas choice and the role of detectors for improving the precision of LIBS analysis are among the topics discussed in this paper.

A procedure for correcting self-absorption in calibration free-laser induced breakdown spectroscopy

Abstract A model of the self-absorption effect in laser-induced plasma has been developed, with the aim of providing a tool for its automatic correction in the Calibration-Free algorithm recently developed for standardless analysis of materials by LIBS (Laser Induced Breakdown Spectroscopy). As a test of the model, the algorithm for self-absorption correction is applied to three different certified steel NIST samples and to three ternary alloys (Au, Ag, Cu) of known composition. The experimental results show that the self-absorption corrected Calibration-Free method gives reliable results, improving the precision and the accuracy of the CF-LIBS procedure by approximately one order of magnitude.

Trace Element Analysis in Water by the Laser-Induced Breakdown Spectroscopy Technique

In this paper, results are presented showing the feasibility of the laser-induced breakdown spectroscopy (LIBS) technique as a fast and sensitive analytic tool for quantitative measurement of trace elements in water. Many ionic elements were detected; the system linearity was tested by analyzing water samples containing known concentration of Mg and Ca, whereas Cr-polluted samples were exploited to test the system sensitivity limit to impurities.

Application of laser-induced breakdown spectroscopy technique to hair tissue mineral analysis

The concentration of the main minerals present in human hair is measured on several subjects by Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) and compared with the results obtained through a commercial analytical laboratory. The possibility of using CF-LIBS for mineral analysis in hair is discussed, as well as its feasibility for the fast and inexpensive determination of the occurrence of heavy-metal poisoning in hair.

Characterization of azurite and lazurite based pigments by laser induced breakdown spectroscopy and micro-Raman spectroscopy ☆

The most commonly used blue pigments in medieval manuscripts are azurite and lapis-lazuli. The first one is a copper-based pigment; the coloring compound of the latter is lazurite, a sodium silicoaluminate in a sulfur matrix. Knowledge of the chemical composition of the materials is essential for the study of illuminated manuscripts. In this paper, micro-Raman and LIBS have been used for the study of azurite and lapis-lazuli, as well as different mixtures of these pigments applied to parchment to simulate an illuminated manuscript. The results of our work show the importance of using more than one technique for a good comprehension of a manuscript. In particular, the Ž. opportunity of combining elemental information obtained from laser induced breakdown spectroscopy and Ž. vibrational spectroscopy information obtained from Raman will be fully exploited. 2001 Elsevier Science B.V. All rights reserved.

Effect of Laser-Induced Crater Depth in Laser-Induced Breakdown Spectroscopy Emission Features:

The influence of crater depth on plasma properties and laser-induced breakdown spectroscopy (LIBS) emission has been evaluated. Laser-induced plasmas were generated at the surface and at the bottom of different craters in a copper sample. Plasmas produced at the sample surface and at the bottom of the craters were spatially and temporally resolved. LIBS emission, temperature, and electronic number density of the plasmas were evaluated. It is shown that the confinement effect produced by the craters enhances the LIBS signal from the laser-induced plasmas.

Self-calibrated quantitative elemental analysis by laser-induced plasma spectroscopy: application to pigment analysis

Abstract A new laser-based spectroscopic technique, called calibration-free LIPS (laser-induced plasma spectroscopy), is proposed for fast and precise elemental analysis in the field of cultural heritage conservation and study. Quantitative stratigraphic results, obtained by CF-LIPS on ancient Roman frescoe samples, are shown. The application of this calibration-free procedure frees the LIPS technique from the need of reference samples or an internal standard. This characteristic, along with the intrinsic speed (the whole process of data collection and analysis takes a few minutes) and precision (of the order of a few parts percent) make the CF-LIPS a viable technique for in situ quantitative analysis of artworks.

Comparative study of two standard-free approaches in laser-induced breakdown spectroscopy as applied to the quantitative analysis of aluminum alloy standards under vacuum conditions

Two standard free approaches to the quantitative analysis of aluminum alloys by laser-induced breakdown spectroscopy (LIBS) are compared—the calibration-free LIBS (CF-LIBS) approach and the Monte Carlo simulated annealing optimization method (MC-LIBS). The experiments are carried out under a pressure of 0.1 mbar, using a Nd-YAG at 1064 nm, with a 5.3 ns nominal pulse width, an energy of 90 mJ/pulse and a spot size on the target of 0.070 cm, resulting in an irradiance of 4.4 GW/cm2. The spectra are taken with a grating monochromator calibrated over a wide spectral range and equipped with an intensified CCD detector. A gate width of 100 ns has been chosen for the measurements. In the MC model, a direct-inverse approach is used, where simulated and experimental spectra are correlated with each other until a satisfactory correlation coefficient is obtained. Spatially resolved measurements are also performed, by recording the plasma emission in the imaging mode and binning the resulting image into 11 different spatial positions along the axial direction, each binned region being equivalent to ∼ 0.025 cm portion of the vertical plasma partition. The spectrum obtained for each spatial position is still spatially integrated along the line-of-sight. Comparatively, concentration values obtained with CF-LIBS for the matrix element Al are much closer to the certified values than those obtained with MC-LIBS (4% versus 20% relative errors, respectively), while the relative concentration obtained for the remainder of the sample components resulted in relative errors that are comparable in magnitude with both approaches (30%–250% relative errors). It is argued that the necessity of improving the space and time resolution of the experimental set-up appears to be at least as important as that of refining the theoretical models.

Basic mechanisms of signal enhancement in ns double-pulse laser-induced breakdown spectroscopy in a gas environment

Understanding the mechanisms of the signal enhancement in double-pulse laser-induced breakdown spectroscopy is highly desirable. It is evident, however, that it is not possible to fit a unique general model to the observations obtained in collinear or in orthogonal geometries, in pre-spark or in re-heating schemes, using ns or fs pulses, in a gas or liquid environment. We believe, instead, that by considering separately the specific experimental cases (for example: a given irradiation geometry, a given pulse timing, etc.) the comprehension of the processes occurring during double-pulse experiments might become easier. We focus on one specific experimental case, namely ns double-pulse irradiation of solid targets in a gaseous environment, and classify the experiments according to the irradiation mode (orthogonal pre-spark, collinear and orthogonal re-heating). Then, we propose a description of the processes occurring in the different cases, on the basis of data and interpretations that are available in the literature.

Quantitative analysis of aluminium alloys by low-energy, high-repetition rate laser-induced breakdown spectroscopy

With the aim of reducing the dimensions of a laser-induced breakdown spectroscopy (LIBS) apparatus for building a portable instrument, a diode-pumped Nd:YAG mini-laser at high repetition rate was tested as an excitation source for the quantitative analysis of aluminium alloy samples. Moreover, LIBS spectra acquired by using an ICCD-echelle spectrometer detection system were compared with those obtained by a traditional spectrometer coupled to a non-intensified linear array detector. Calibration curves were built and limits of detections were calculated using both detection systems for magnesium, silicon, copper, titanium, manganese, nickel and iron. The results were compared with those obtained by recently proposed LIBS systems based on the use of microchip lasers.