Insight into the interaction of the microwave radiation with droplets of interest in analytical chemistry

The idea of heating aerosols by applying a microwave field has recently been taken up again for liquid sample introduction in atomic spectrometry. Heating of the droplets can take place directly, because of microwave energy absorption by the droplets themselves, or indirectly, as a result of heat transmission from the radiated parts of the system to the droplets by conduction, convection or thermal radiation. There is some degree of discrepancy among the specialists on this subject, i.e., about the contribution of each of these mechanisms to the temperature of the aerosol. Some of them state that there is no direct coupling between the microwave radiation and the droplets, only indirect heating. However, we claim that both ways of heating occur. In this work we support our point of view on the basis of the existing bibliographical background, a theoretical analysis and our own experimental results.