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Polarization of Atomic Fluorescence in Flames

Volume 25, Number 1 (Feb. 1971) Page 97-97

Shull, M.; Winefordner, J.D.

During a recent investigation of the use of polarizers in atomic fluorescence flame spectrometry, some interesting observations were made. The study was begun because it was felt that crossed polarizers (one polarizer between the source and flame and one polarizer between the flame and monochromator) could be used to great advantage in analytical atomic fluorescence flame spectrometry by reducing the fraction of source radiation scattered from particles in the flame gases in relation to atomic fluorescence from the analyte atoms. According to other investigations of polarization in gases at high pressures, it seemed reasonable to expect atomic fluorescence to be unpolarized and scattering to be polarized. Using electrodeless discharge tube sources for Ga and Cd, polarizers, either an H2/N2O or an H2/air premixed turbulent flame, and the experimental setup of Mansfield et al., we found that the fluorescence signals were reduced to the same extent as the scattering signal when the polarizers were parallel or perpendicular. The percentage degree of polarization for atomic fluorescence (Cd-2288 Å and Ga—4172 Å) and for scattering from water droplets as well as particles in the flame gases was found to be 100% within the accuracy of the measurement for a wide range of Cd (0.01-1 μg/ml) and of Ga (10-100 μg/ml) concentrations sprayed into the flame. These results were surprising to the authors and disappointing from the standpoint of analytical atomic fluorescence flame spectrometry because of the failure of polarizers to minimize scattering in the presence of atomic fluorescence.