Spatially Resolved Laser Induced Breakdown Spectroscopy in Orthogonal Double Pulse Configuration and Laser Ablation Inductively Coupled Plasma Mass Spectrometry of Archaeological Findings

Local analysis of dental calcified tissues plays important role in medicine, toxicology, environmental science, paleontology and anthropology. In these fields of action a bulk analysis of a mineralized material from a defined and welllocalized volume belongs to a marginal stream. On the other hand, spatially resolved analyses of calcified tissues as teeth or bones without any previous decomposition have been routinely performed with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), X-ray fluorescence (XRF), particle (proton) induced X-ray emission spectroscopy (PIXE), secondary ions mass spectrometry (SIMS) or even formerly electron microprobe analysis (EMP). Nowadays, Laser Induced Breakdown Spectroscopy (LIBS) becomes a widely employable technique in analytical chemistry. It can be used for elemental analyses of samples of any state (i.e. gas, solid and liquid). In last ten years the double pulse configuration (DP) became a great importance due to some advantages as intensity enhancement of emission lines. Up to now, several combinations were tested. The four basic are: i) two consequent coaxial laser pulses (but perpendicularly to the sample) – the first one ablates the sample and the second one even more feeds the microplasma induced by the first one, ii) the first one ablates the sample and the second one feeds the plasma perpendicularly, iii) the first pulse is collinear with the sample and induces a plasma by a breakdown of the atmosphere and the second one strikes the sample perpendicularly through the breakdown plasma, iv) any other spatial non-orthogonal configuration. The typical time gap between the pulses is 1–10 μs. Due to a transient behaviour of the microplasma some non-linear effects occur at analytical measurements with LIBS and finally demonstrate themselves as nonlinear calibration curves (intensity vs. element content). These phenomena are matrix-dependent and limit the use of LIBS to mostly semi-quantitative precision. Nevertheless, it is commonly used for in situ analysis of cultural heritage objects. For spatially resolved analysis of bones and teeth it has been still rarely used. The main advantage of the DPLIBS is a substantial enhancement of the sensitivity against the single pulse LIBS. This approach is still rarely applied to analysis of artifacts. To the best knowledge of the authors the DP variant has been never used for the analysis of calcified tissues. Thus, one can expect that a valuable comparison of LAICP-MS with DPLIBS will be to some extent feasible. This is also the main goal of this work. It aims to compare whether the spatial distributions of some major and minor elements in a reindeer tooth section yielded by both the methods are equivalent.