Characterization of an Interelement Enhancement Effect in a dc Plasma Atomic Emission Spectrometry System

Abstract

The enhancement of atomic and ionic emission in a dc plasma due to the addition of easily ionized elements has been studied. The results show that the addition of the concomitants: (1) causes enhancements in both atomic and ionic emission, (2) does not cause significant changes in the electron temperature or the electron population of the plasma excitation zone, (3) results in a downward shift in the rotational temperature of that zone, and (4) does not cause significant changes in the efficiency with which analytical species are delivered to the plasma. These observations indicate that the enhancement effect cannot be readily explained based on plasma temperature increases or the classical ionization repression mechanism. As an alternative, it is suggested that the enhancement may result from increases in the population of metastable argon with coincident increases in excitation via collision with this species. This mechanism is circumstantially supported by the present results but must be regarded as tentative.