Qualitative Analysis using ICP-AES:

In principle it is possible to obtain qualitative information from ICP emission spectrometry by using sequential spectrometers. However, this technique has not been exploited for the purpose. This is so why the amount of sample and instrument time required is prohibitive. Same, as it is almost impossible to install individual photomultipliers to monitor multiple lines for each possible element of interest the direct reading spectrometers or polychromators are also not used for qualitative analysis. Yet the method has the potential and is used to some extent for qualitative purposes.

The qualitative analysis is based on the principle that each element has a characteristic spectrum consisting of the most persistent lines and the characteristic lines. These are used to identify the presence of an element in the analyte. The most persistent or RU (raies ultimes) lines are the ones that persist even when the concentrations of the respective elements are progressively reduced to zero.  The RU lines are not necessarily the most intense lines. For example, within manganese spectrum, a triplet at 279.8 nm is more intense at normal concentrations than the 403.3 nm triplet, but the latter are the three most persistent lines for manganese. Additionally each element has a set of characteristic line groupings such as doublets, triplets, groups of doublets, etc. However, for an element the characteristic line groupings do not necessarily consist of the most persistent lines. For example, a most persistent line for magnesium is the single line at 285.213 nm, although the characteristic magnesium emission occurs at 277.62782 nm.