Calibration Free ? Laser Induced Breakdown Spectroscopy (CF-LIBS)

MONCAYO SAMUEL; PLAVČAN J, VEIS P, HORŇÁČKOVÁ M; BORGNINO LAURA; CACERES J.O.

Conferencia; 8º International Conference on Laser Induced Breakdown; 2014

Volcanic eruptions cause serious environmental problems, the most harmful effects are produced by toxic gases such as carbon dioxide, sulphur dioxide and especially volcanic fly ashes, which travel thousands of kilometres and cover vast areas of land with a toxic layer of dust [1]. The composition of the ashes differs according to the volcanic region and its internal geological processes. These ashes are mainly composed of SiO2 and Al2O3 and usually contain other elements such as Fe, Na, Ca, Mg and Ti in lower amounts. Some trace elements like Cr, Mn, Pb, Sr, Ni, As and F are also typically found [2]. As and F are the more important contaminants regarding environmental and health issues as they cause diseases that affect the population. Arsenic species migrate into the soil and often get to underground aquifers contaminating drinking water. In this work, volcanic ash samples collected from the south of Argentina in three different eruptions (Hudson, Chaitén and Puyehue volcanoes) were analysed using LIBS. In previous LIBS studies, calibration curves were used in the detection of As in groundwater in the order of ppm using ZnO as an adsorbent and concentration enhancement technique by pre-boiling [3]. In this case all samples were solid and the concentration enhancement was not possible. All samples were prepared in pellets in order to get a homogenous and resistant surface.The LIBS spectra were recorded using a broadband (200-975nm) Mechelle spectrometer (ME5000,Andor) and a high-resolution spectrometer (THR 1500, JobinYvon) coupled with an iCCD (iStar, Andor) and an EMCCD (Newton, Andor) cameras, respectively. Plasma parameters such as electron density and temperature were calculated on the base of Stark broadening mechanism of H alpha spectral line and Saha- Boltzmann plots of Si and Mg lines using of broadband LIBS spectra. After that average temperature was taken into account for the quantification of major and minor elements (Fe, Si, Na, Ca, Mg, Ti,?) and trace element As in three samples of volcanic ashes using of a Calibration Free (CF) approach of LIBS. Obtained results were compared with ICP-MS measurements.