Interferometric droplet imaging for in situ aerosol characterization in an inductively coupled plasma

Abstract

Size, velocity and evaporation rate of droplets in an Ar inductively coupled plasma (ICP) are simultaneously measured for the first time using a novel laser based imaging technique. In interferometric droplet imaging (IDI), an interference pattern created by the reflected and refracted rays from a droplet are collected in an out-of-focus image. The droplet diameter is determined by counting the number of fringes in the collected interference pattern. Combination of IDI and particle tracking velocimetry (PTV) provides the capability of monitoring droplet properties during the journey inside ICP. Using a demountable-direct injection high efficiency nebulizer, droplets in the range of 3-30 mm in diameter traveling at 15-70 m s À1 are observed in the analytical zone of the ICP. The upper velocity threshold for surviving droplets is determined by the nebulizer gas flow rate, whereas the lower threshold is mainly influenced by thermal expansion of the plasma gas. Droplet evaporation rates (0.26-0.36 mm 2 s À1 ) are in good agreement with other reports and theoretical simulations for droplets in a 3000 K Ar environment.

Inductively coupled plasma-mass spectrometry: insights through computer modeling

“…51,52 A comparison between the dried solution aerosols from a microconcentric nebulizer and solid particles from LA was also performed by the groups of Houk, Montaser and Niemax. [53][54][55] Montaser and coworkers determined the droplet velocities in the ICP by means of particle image and particle tracking velocimetry. 54 Niemax and coworkers investigated the effect of injector gas flow rate, droplet diameter and amount of analyte on the spatial positions of analyte atomization and ionization, by means of end-on and side-on OES and applying monodisperse microdroplets (MDMDs).…”

“…[53][54][55] Montaser and coworkers determined the droplet velocities in the ICP by means of particle image and particle tracking velocimetry. 54 Niemax and coworkers investigated the effect of injector gas flow rate, droplet diameter and amount of analyte on the spatial positions of analyte atomization and ionization, by means of end-on and side-on OES and applying monodisperse microdroplets (MDMDs). [55][56][57][58] Finally, Günther and colleagues applied 2D OES and ICP-quadrupole (Q)MS of individual particles, to study the evaporation process of laser-produced aerosols and the subsequent diffusion losses inside the ICP, 59,60 and they reported that larger particles may vaporize incompletely or at different axial positions inside the ICP because of composition-dependent melting and vaporization enthalpies.…”

Local effects of atomizing analyte droplets on the plasma parameters of the inductively coupled plasma

“…In the last decades, the processes essential in sample introduction and atomization have been studied independently by different research groups [5][6][7][8][9][10][11][12][13][14][15][16]. In particular the investigations with monodisperse droplets generated from aqueous analyte samples of known concentrations [5][6][7][8][9][10][11] gave a deeper insight into the interaction processes of analyte and plasma.…”

Particle transport through an inductively coupled plasma torch: elemental droplet evaporation

“…17 Particle effects in laser ablation (LA) ICP-MS were studied and the dried solution aerosols from a microconcentric nebulizer were compared with solid particles from LA. [18][19][20] Moreover, Jorabchi et al 21 applied Mie scattering to determine the droplet velocities in the ICP from particle image velocimetry and particle tracking velocimetry.…”