Measurement of monodisperse droplet desolvation in an inductively coupled plasma using droplet size dependent peaks in Mie scattering intensity

The periodic fluctuations in the Mie scattering intensity as a function of droplet diameter due to constructive and destructive interference of light reflected/diffracted from the droplet surface and light transmitted/refracted through the droplet were used to measure the desolvation rate of isolated water droplets in an inductively coupled plasma. The approach is applicable to study the desolvation of isolated, monodisperse droplets and does not require measurements as a function of wavelength or scattering angle. Use of a near forward scatter angle provides high intensity signals. Among the limitations of this measurement technique is the need to identify the absolute droplet diameter at one time during desolvation either by another droplet size measurement technique or by matching the pattern of Mie scattering intensity as the droplet evaporates to the theoretical intensity pattern. The results show that the droplet desolvation rate is not affected by the addition of 0.1 M NaCl to the sample even though the initial emission occurs earlier in time than when the sample does not contain a high matrix concentration. The measured droplet desolvation rates are higher than those reported by two previous publications but further measurements are needed to confirm the preliminary results reported here.