The analysis of the shape of analytical curves in Zeeman atomic absorption spectroscopy has been extended towards very high concentration. Beyond the absorption maximum the slope of the Zeeman analytical curve depends on the remaining absorption at maximum field strength. The absorbance and concentration at roll-over can be estimated from the initial slope of the Zeeman analytical curve at low concentration and the decreasing part of the curve at very high concentration. It is shown that the dynamic range of atomic absorption analytical curves can be readily extended with an ac Zeeman system. Analytical curves of reduced sensitivity are obtained when the maximum field intensity measurement is combined with a measurement at intermediate field strength rather than at zero field strength. However, the maximum absorbance in the extended range Zeeman analytical curve is lower than in the normal Zeeman analytical curve.
M. T. C. De Loos-Vollebregt and L. De Galan, "The Shape of Analytical Curves in Zeeman Atomic Absorption Spectroscopy III: Extended Dynamic Range," Appl. Spectrosc. 38, 141-148 (1984)