Studies of chemical interferences in an inductively coupled plasma using moment analysis of space-resolved emission profiles.
Interelement effects induced by sodium, aluminum, and phosphate ion on calcium and magnesium emission were studied with a two-channel spectrometer that could record spatially resolved emission profiles of an atom line and an ion line simultaneously. The statistical moments of the digitized emission profiles were calculated and were employed for rate-constant estimation using our previously established theory. Interelement effects are results of interferences in the analyte atomization, ionization, and/or recombination steps. Characteristic changes will be induced in the emission profiles by each of these interferences. These changes can be characterized by the statistical moments of the corresponding profiles. Therefore, by investigating variations in the rate constants caused by the specific concomitant, one may better understand the analyte atomization-excitation mechanisms. Sodium enhances the atomic emission of both calcium and magnesium but has little effect on their ionic emission. Based on the trends of variation in the rate constants, the atomic signal enhancement seems to be attributed more to the facilitation of analyte atomization rather than to the shift of ionization equilibrium. Aluminum and phosphate ion appear not to induce significant interferences on either elements.