Studies of a radio frequency inductively coupled argon plasma for optical emission spectrometry—III. Interference effects under compromise conditions for simultaneous multi-element analysis☆

Abstract This work concerns interference effects in a 0.7-kW, 50-MHz inductively coupled plasma (ICP) provided with an ultrasonic nebulizer (USN) and desolvation apparatus (DA). The observations were made under (ICP) conditions adopted previously as “compromise conditions for simultaneous multi-element analysis.” Various matrices and analytes were considered. An arrangement of two identical USN's with separate DA's was used to distinguish between interferences due to processes in the plasma (“plasma effects”) and the nebulizer—desolvation apparatus (“nebulizer—desolvation effects”). The latter were identified as “desolvation effects” and attributed to a variation in the loss of analyte in the DA. This desolvation effect, whose magnitude varies between ±10%, is related to the difference in volatility between matrix and analyte. The experiments revealed plasma effects that cannot be reconciled with the common pictures of ionization interference and are not due to incomplete volatilization or dissociation either. Possible explanations are considered. The overall interference level in the ICP studied is discussed and practical conclusions regarding the use of desolvation, “pure” aqueous solutions as standards, and spectroscopic buffers are drawn.