Mechanisms of selenium vaporization with palladium modifiers using electrothermal atomization and mass spectrometric detection

Abstract

Mass spectrometric sampling of gaseous species that evolve from graphite flats and tubes that are pulse heated In vacuo and from graphite tubes that are pulse heated at 1 atm of pressure was employed in order to elucidate mechanisms controlling selenium electrothermal atomization. Investigations were performed (I) without modifier, (II) with thermally reduced palladium modifier, and (ill) with nonreduced palladium modifier. Selenium oxides, carbides, hydroxides, dimer, free atom, and palladium were observed as a function of time and temperature during the atomization cycle. The reduced palladium modifier eliminated formation of the molecular selenium species except selenium monoxide. Both SeO and Se02 were observed when the nonreduced palladium modifier was involved. In both cases, palladium forms a stoichiometric compound with selenium that retains the selenium until higher temperatures are reached.

Release of selenium and tin from the graphite support in the presence of tungsten and palladium modifiers

“…The existence of various compounds between Pd and Se or Sn is shown using the different instrumental methods -SEM, ~tEDXRD [14][15][16]. Indirectly the possibility to form [Pd, Se, O] species during pyrolysis and vaporization of Se from that mixture also was shown by scanning electron microscopy [17].…”

Effect of nickel and palladium as chemical modifiers and influence of urine matrix on different chemical species of selenium in electrothermal atomic absorption spectrometry

“…Selenium, introduced into the furnace as SeIV desorbs from a graphite surface as SeO,, SeO, Se, and Se(OH), at around 400 K,I9-,I which dissociate in the gas phase to atomic selenium at 1000,20 1 1 75,' or 1600 K. 19 Charring curves for selenite and trimethylselenonium in the absence of a modifier are shown in Fig. 1.…”

Sample transformation at two-stage probe atomization in graphite furnace for atomic absorption spectrometry

“…Механизм его ато-мизации в графитовой печи не очень сложен. Он изучен с применением масс-спектрометрии [19], которая обнаружила в газовой фазе графитовой печи только пар металла. Следовательно, эта про-ба должна формировать конденсат атомного пара металла на зонде без участия каких-либо соедине-ний палладия.…”