MASS-ACTION CONTROLLED IONIZATION OF INDIVIDUAL SOLUTE VAPOR CLOUDS IN FLAME SPECTROMETRY

A stream of nearly identical droplets of CaCl2 or Mn(N-O3)2.4H2O solution is introduced along the axis of a N2O-C2H2 flame supported on a circular slot burner. Radial scans of the emission intensity of Ca and Mn at various heights in the vapor cloud are used to obtain information on the size and shape of the cloud as well as on changes in the total number of emitting species with height in the cloud. Results for Ca show a more than 50 % decrease in intensity 70 mm above the origin of the vapor cloud relative to 19 mm where the intensity is maximum. It is shown that much of this decrease in neutral-atom line intensity can be accounted for by the effect of mass action on ionization as the vapor clouds from the individual solute particles expand by isotropic diffusion. Further, it is shown that diffusion is slow relative to convection as a mass transport process. This permits the extension of the mass-action controlled ionization concept to conventional nebulizers, where ionization interference frequently is observed to increase with increasing height above the primary reaction zone in the flame. © 1979, American Chemical Society. All rights reserved.