Development of direct elemental speciation in solid state materials using pulsed glow discharge mass spectrometry

Among the various elemental mass spectrometry techniques, glow discharge mass spectrometry is recognized for its ability to provide direct determination of trace elements present in solid state samples. In the present work, a pulsed glow discharge time of flight mass spectrometry method is developed for the direct speciation of chromium in solid state samples. In initial investigations, time-resolved power perturbation and Langmuir probe studies were undertaken to elucidate the excitation and ionization processes in a pulsed glow discharge plasma. The experimental data provides further insight into the energy transfer processes that occur at different spatial locations and in different temporal regimes of these pulsed glow discharge plasmas. Of greatest interest is the afterpeak regime, in which dissociative recombination between molecular argon ions (Ar2+) and electrons is thought to be the principal process responsible for emission enhancements. Careful tuning of the operating parameters within this time regime yields the plasma chemistry that favors cluster ion formation. Unique mass spectral features found in the afterpeak permit differentiation between the trivalent and hexavalent forms of chromium, (CrIII) and (CrVI) respectively, in chromium oxide samples