XPS Characterization of Bi and Mn Collected on Atom-Trapping Silica for AAS

The chemical state of analyte species collected on a water-cooled silica tube during atom-trapping atomic absorption spectrometric determination is investigated with the use of X-ray photoelectron spectroscopy (XPS) for Bi and Mn. Analysis of the Bi 4f 7/2 peak reveals that the chemical state of Bi is +3 during initial trapping (before the atomization stage), but an additional 0-valence state of Bi is also observed after the atomization stage. With the use of the measured Mn 2p 3/2 binding energy together with the observed 3s multiplet splitting, the chemical state of Mn is determined as +2 in all stages. Together with our previous determination of 0 valence for Au, it is now postulated that the stability of certain valence states of the three elements (Au, Bi, and Mn) on the silica matrix can be correlated to their electrochemical reduction potentials.