EASILY IONIZABLE ELEMENT INTERFERENCES IN INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROSCOPY .1. EFFECT ON RADIAL ANALYTE EMISSION PATTERNS

The spatial emission patterns of Ca I and Ca II in an inductively coup led plasma (ICP) arc altered when an easily ionizable element (EIE) is added to a sample solution. As a result, unanticipated interferences can arise in ICP-AES when EIEs of unknown identity or concentration ar e present. The EIE effect was investigated here by two-dimensional lat eral mapping of Ca atomic and ionic emission by means of a monochromat ic imaging spectrometer. Lithium served as the EIE at added concentrat ions from 0 to 1000 mug/ml. The resulting Ca radial emission images, c alculated by Abel inversion, displayed in most regions a linear change in intensity with Li concentration. In regions of highest calcium emi ssion, however, the EIE influence on Ca emission signal becomes marked ly non-linear and is better fit with a logarithmic function. Principal -component and regression analysis of these EIE-altered images offers some insight into possible mechanisms of the EIE effect.