A paper recently published in this journal provides a thorough discussion of intra-alkali matrix effects that occur in the initial radiation zone (IRZ) of the inductively coupled plasma; the matrix effects described are of the analyte emission enhancement type. Despite such matrix effects, the authors conclude that the IRZ is the preferred viewing zone during alkali metal determinations because maximum emission occurs in this zone; the method of standard additions is then suggested to correct for intra-alkali matrix effects.
Danton D. Nygaard and David A. Leighty, "The Optimal Viewing Zone for Alkali Metals in the Inductively Coupled Plasma," Appl. Spectrosc. 39, 353-354 (1985)