Abstract

The matrix effect of easily ionizable elements (EIEs) on emission intensity of 35 analytes (Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cs, Cu, Fe, Ga, Hg, In, Li, Mg, Mn, Mo, Ni, P, Pb, Pd, Pt, Sb, Se, Sr, Ti, Tl, V, Zn and Zr) in an argon microwave induced plasma (MIP) was studied in order to find a more complete picture of analyte behaviour in this type of excitation source. The low-power MIP-AES system based on a TE₁₀₁ rectangular cavity and a laboratory-made ultrasonic nebulizer without a desolvation unit was utilized under such operating conditions (applied power 130 W, argon flow rate 200 ml min⁻¹) in which a pronounced effect could be achieved, and particular excitation mechanisms could be easily distinguished. When taking into account the character of the signal response on the increasing sodium concentration, the elements studied can be divided into four groups. Various collisional processes, a shift in ionization equilibrium, or a volatilization effect may play a dominating role in the overall matrix interferences depending on the nature of the analyte. Argon metastables as well as electrons and atoms resulting from the EIEs are presumed to contribute in the analyte excitation.