High speed LIBS on prehistoric animal teeth

M. Galiová, et al., from the Masaryk University used the 4 Quik 05 ICCD camera for laser induced breakdown spectroscopy (LIBS). The team used LIBS in combination with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for multi-elemental analysis of prehistoric animal teeth.

Laser-induced breakdown spectroscopy (LIBS) multi-elemental analysis of prehistoric animal teeth.

The prepared canine tooth of a fossil brown bear (Ursus arctos) is shown on the upper left image. The maps showing the of Ca distribution and Sr=Ca, Sr=Ba ratios obtained with quantitative LA-ICP-MS mapping. The Sr=Ca and Sr=Ba ratios were normalized. The bar has a length of 500μm. Reprinted from Applied Optics, Vol. 49, Issue 13, pp. C191-C199 (2010) with permission from The Optical Society.

Element analysis using Laser induced breakdown spectroscopy (LIBS)

Laser induced breakdown spectroscopy (LIBS) is a method of atomic emission spectroscopy. Usually, a laser is focused on the sample an generates a plasma on its surface. The atoms within the plasma are in the excited state and emit light of characteristic frequencies. In principle, this method can be applied to detect all elements. LIBS is only limited by the power of the excitation source and the sensitivity of the spectrograph in combination with the detector. The 4 Quik ICCD cameras provides the highest sensitivity down to single photon detection which is necessary to achieve high resolution spectra and high S/N ratios. Furthermore, the combination of LIBS and LA-ICP-MS allow fast multi-elemental analysis of a broad variety of matrices.

Experimental Laser induced breakdown spectroscopy instrumentation

LIBS analysis for this publication was performed in the laser laboratory at the University of Malaga (Spain). A microplasma is generated on the sample surface by a frequency doubled, Q-switched Nd:YAG laser at 532nm and 5ns pulse width. The Plasma emission was collected by a fiber optic and guided onto the Czerny-Turner imaging spectrograph. On the output of the spectrograph the 4 Quik intensified CCD camera providing a spectral resolution of 0.02 nm per pixel. The 4 Quik camera was controlled with the 4 Spec software. The individual LIBS spectra were acquired in the spectral window from 253nm to 617nm. Typical single-shot LIBS spectra are shown in the figure below. For LIBS line scanning the spectra are averaged from seven shots fired to the same position after performing three cleaning shots.

Single-shot laser induced breakdown spectroscopy (LIBS) spectra.

Typical single-shot laser induced breakdown spectroscopy (LIBS) spectra of microplasma created by focusing the laser beam with an energy of∼90mJ per pulse. The spectra were recorded with delay and integration times of 1 and 10μs, respectively. Ba, Sr, and Ca lines were measured with a1200groove mm-1 grating; Na and Fe lines were measured with a 2400 groove mm−1 grating. Reprinted from Applied Optics, Vol. 49, Issue 13, pp. C191-C199 (2010) with permission from The Optical Society.

Results of LIBS line scans and mapping

The line scans derived from LIBS and LA-ICP-MS analysis of macro element Na and trace element Fe are compared in the figure below. Both techniques determine similar accumulation for all the tracked elements across the scanned lines. The graphs show similar behavior of elemental distribution inside the dentine to that reported in the literature.

LIBS and LA-ICP-MS comparison on a cross sections of fossil brown bear.

The colored area in figure (a) shows the position of LIBS (1) and LA-ICP-MS (2) line scans. The graphs below show the comparison of the elemental distribution of (b) Na and (c) Fe obtained from the cross sections of fossil brown bear (Ursus arctos) canine tooth dentine. Reprinted from Applied Optics, Vol. 49, Issue 13, pp. C191-C199 (2010) with permission from The Optical Society.

LIBS proved successfully its spatially resolved analysis capability

Laser ablation-based analytical techniques were successfully applied for mapping and line-scanning a fossil animal tooth section. Laser-induced breakdown spectroscopy (LIBS) similar to LA-ICP-MS, proved to be suitable for fast, spatially resolved analysis. The authors of this publication have shown that LIBS and LA-ICP-MS can be successfully used as complementary techniques in spatially resolved microchemical analysis of fossil samples. Furthermore, the 4 Quik ICCD camera enhanced the sensitivity of the LIBS setup due to it excellent – down to single photons – sensitivity.

Title: Multielemental analysis of prehistoric animal teeth by laser-induced breakdown
spectroscopy and laser ablation inductively coupled plasma mass spectrometry

Author: Michaela Galiová, et al.
Institute: Masaryk University, Czech Republic