7. Measuring the net intensity of an analysis line

In order to take into account any variations in background, especially when the latter is significant, as in the case of ICP plasma, it may be necessary to accurately measure the background-corrected intensity of the analysis line. In all cases, it is necessary to measure the raw intensity. To do this, either the bandwidth is smaller than the physical width of the line, and the spectral band must therefore be located at the maximum of the line, or the bandwidth is wider than the line, and it is sufficient for the line to be included in the spectral band. The latter is the most general case. It is also necessary to measure the background intensity, which can then be deducted from the raw intensity to obtain the net intensity. Two cases need to be considered: the polychromator case and the monochromator case.