An evaluation of a commercial Échelle spectrometer with intensified charge-coupled device detector for materials analysis by laser-induced plasma spectroscopy

Abstract

In this work we evaluate the performance of a commercial Échelle spectrometer coupled with an intensified charge-coupled device (ICCD) detector for the analysis of solid samples by laser-induced plasma spectroscopy (LIPS) in air at atmospheric pressure. We compare results obtained in aluminum alloy samples with this system and with a ‘conventional’ Czerny-Turner spectrometer coupled to an intensified photodiode array (IPDA). We used both systems to generate calibration curves and to determine the detection limit of minor elements, such as Mg, Cu, Si, etc. Our results indicate that no significant differences in terms of analytical figures of merit exist between the Échelle/ICCD system and a conventional Czerny-Turner spectrometer with IPDA. Moreover, measurements of plasma temperature and electron density using the two assemblies give, in general, very similar results. In the second part of this work, we aim to present a critical view of the Échelle spectrometer for LIPS applications, by drawing up the balance sheet of the advantages and limitations of the apparatus. The limitations are either inherent to the dispersion method, or result from the dynamic range of the detector. Moreover, the minimum ICCD readout time does not allow a fast data acquisition rate. On the other hand, the Échelle spectrometer allows complete elemental analysis in a single shot, as spectral lines of major, minor and trace constituents, as well as plasma parameters, are measured simultaneously. This enables a real-time identification of unknown matrices and an improvement in the analytical precision by selecting several lines for the same element.