Some unexpected interferences in flames

A series of interferences has been observed in emission and absorption for rare earth elements in the nitrous oxide-acetylene flame and for some first row transition elements with air and acetylene. Signal changes, mostly suppressions, are observed at low (ppm) concomitant levels with the degree of interference consistently showing an abrupt slope change at mole ratios of concomitant to analyte element of between 1-1 and 2-1. The effects are observed for high boiling, oxygen containing mineral acids and for many organic compounds which contain oxygen and which decompose instead of vaporizing when heated. Some non-volatile, nitrogen containing compounds also give suppressions but here the behavior is less consistent. The effects are very sensitive to flame richness and often can be overcome by proper fuel to oxidant ratios. Also, the effects are much more severe when only analyte and concomitant are present in contrast to solutions containing other salts, i.e. a sample matrix. Though we cannot yet offer a complete explanation for the suppressions, definite stoichiometry is indicated in reactions involving the solid phase after desolvation and prior to vaporization.