Panoramic laser-induced breakdown spectrometry of water

Wide spectral range time resolved laser-induced breakdown spectroscopy has been investigated to evaluate its potential for simultaneous determination of major, minor and trace concentrations in water. A combination of echelle spectrometry with a time gated intensified charge coupled device camera (ICCD) facilitated such working conditions. Multi-elemental panoramic line spectra (200–1000 nm) have been analyzed at different delay times td (0.2–10 μs) and gate widths tw (1–10 μs). The evolved laser-induced plasma in water has been followed up temporarily and spatially. The behavior of the obtained curves is found to be, in general, analyte-dependent. Other physical parameters such as plasma temperature Te and electron density Ne are determined from the spectra obtained under the optimized experimental conditions. Aqueous Na and Mg solutions of different concentrations were used to construct calibration curves and estimate the limit of detection (LOD) of the measurements. Other calibration curves for each of the two elements in mixed solutions are used to evaluate the matrix effect on the LOD. In all cases the calibration curves showed good linearity within two orders of magnitude. The lowest detection limits (1 and 2 μg ml−1) are obtained for Mg and Na in pure solutions, respectively, while slightly higher LOD values (1.2 and 2.5 μg ml−1) are determined for the same elements in the mixed solution. To assess the accuracy of such panoramic LIBS measurements, Mg and Na concentrations in bottled potable water have been determined and good agreement between the measured and labeled values is obtained.