Analysis of various elements in solutions containing high concentrations of a base metal, is a challenge using ICP-OES techniques. The challenge basically consists of reaching required limits of quantification (LOQ). The use of higher concentrations in order to reach lower LOQ’s is not always a solution due to more matrix effects in the plasma and increased spectral interferences of the base metal. Notorious matrices are iron (Fe), molybdenum (Mo), tungsten (W) and uranium (U), being elements that have a very strong emission lines or are very line rich. Fe has a total of 12599 atomic (I) and ionic (II) wavelengths between 200 and 760 nm and tungsten has 9195 lines. Molybdenum is not as line rich but has relatively many very strong wavelengths that make it difficult to analyse other elements in this matrix.

Currently the metals industry uses Argon based ICP-OES systems having to deal with spectral interferences from the base elements. Many of these interferences are caused by the fact that due to its relatively high plasma temperature of 6000 – 7500 K, many if the lower sensitivity matrix lines are excited. As a nitrogen based plasma is typically 1000-1500 K lower in temperature, there may be differences in terms of less matrix and wavelength interferences. This study compares some figures of merit of using Argon- and Nitrogen-based ICP-OES systems.