Behaviour of a desolvation system based on microwave radiation heating for use in inductively coupled plasma atomic emission spectrometry

Abstract

The present paper describes the preliminary results obtained with a desolvation system for inductively coupled plasma atomic emission spectrometry that incorporates a heating unit based on microwave (MW) radiation. This system has been called Microwave Desolvation System (MWDS). The results have proved that MW radiation can be considered as a good choice for aerosol heating in a sample introduction system. MW radiation seems to be a more uniform way of aerosol desolvation than conductive/convective heating (i.e. lower radial temperature gradients), the degree of vaporization of the droplets is less dependent on the liquid flow rate ( Q l), and also the background noise associated with the vaporization of droplets is reduced. As regards the results obtained with MWDS, in comparison with a conventional desolvation system (CDS), they are very dependent on Q l. When heating is applied, the amount of analyte that leaves the heating step increases by 30–60% with the MWDS, irrespective of Q l, whereas for the CDS this increase is very high (up to 300%) at low Q l values (0.4 ml min −1), but almost negligible at high Q l values (2.4 ml min −1). In agreement with this, the analytical figures of merit are favourable to the CDS at low flow rates, and to the MWDS at high liquid flows. Under all the conditions studied, the amount of solvent that leaves the condensation unit are lower for MWDS than for CDS.