Interference caused by indium in the atomization of Ag, Bi, Cd, Sn, and Tl in ETA-AAS

The depression of the signals for Ag, Bi, Cd, Sn, and Tl trace determination by ETA-AAS, which occurs in the presence of hydrobromic acid (with or without indium present), has been investigated by use of a new combined atomization equipment, molecular absorption measurements and thermodynamic calculations. The results show that all these elements form easily volatile bromides and more or less stable diatomic molecules of MBr type. These diatomic molecules, formed in the gaseous phase, are removed from the observation volume by diffusion, before their dissociation is complete. These two effects-formation of easily volatile compounds and stable diatomic molecules-are the main reasons for the depression of the atomic-absorption signals.