INVESTIGATION OF THE FORMATION OF SOLID-PHASE COMPOUNDS BETWEEN TELLURIUM AND INTERFERING ELEMENTS IN GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY

A new method is proposed here to investigate the formation of solid ph ase compounds between the analyte and the interfering elements during atomization in a graphite furnace. Microgram amounts of the analyte ar e placed in a crucible and mixed with a 100- or 1000-fold excess of th e concomitant element. The crucible is then introduced among the waps of an induction furnace and heated in a stream of argon, according to a temperature program analogous to that employed in the atomic absorpt ion procedure. The temperature is controlled by a chromel-alumel therm ocouple fixed on the crucible, the heating is stopped during the tempe rature ramp, before the atomization of the mixture, and the resulting solid phase is studied by surface analysis techniques (optical microsc opy, scanning electron microscopy, energy dispersive spectrometry, X-r ay microdiffractometry). This method has been applied to the study of the formation of compounds between tellurium and Na or K. The effect o f a chemical modifier (Ni or Pd) has also been studied by adding it to the crucible together with the interfering element. Finally, an attem pt is made to elucidate the role of the carbon by replacing the graphi te crucible with a tantalum one. (C) 1997 Elsevier Science B.V.