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Computational Modelling of the Volatile Hydride Fragmentation in a Dielectric Barrier Discharge Atomizer

[ Vol. 16 , Issue. 3 ]

Author(s):

Wameath S. Abdul-Majeed and William B. Zimmerman   Pages 210 - 222 ( 13 )

Abstract:


In this study, we present a model whereby a fragmentation of arsenic hydride in a rectangular dielectric barrier discharge (DBD) atomizer is investigated. The aim is to elucidate the distribution of the intermediates species and generated free analyte atoms along atomizer channel, which is required to decide the optimal position for spectrometric data acquisition. Simulation results indicate that formation of intermediate species and free arsenic atoms is initiated in the first section of atomization channel before reaching the section between the electrodes. Moreover, concentration of free arsenic atoms saturates to a maximum and does not vary thereafter along atomization channel. This result could be attributed to the presence of abundance of hydrogen radicals along atomization channel which limits recombination reactions and ultimately maintains free atom life, which is so useful for analytical purposes. This outcome suggests an approach for radial data acquisition from any position along DBD atomization channel with same sensitivity. Furthermore, this result indicates that DBD atomizer is appropriate for analytical purposes and competitive to other well known atomization tools such as a quartz cell atomizer. The model has been verified experimentally upon examining arsenic and mercury qualitatively from applying chemical vapour generation techniques. Approximately similar results obtained from three radial positions along the atomization channel, whereas a significant increase in signal intensity observed when applying axial viewing by 22 and 40% for arsenic and mercury respectively.

Furthermore, a quantitative determination for arsenic is also tried; however, the results were found not useful for model validation due to the hydrogen magnification effect on the recorded spectrum.

Keywords:

Absorption spectroscopy, arsenic hydride, chemical vapour generation, DBD plasma atomizer, emission spectroscopy, plasma chemistry

Affiliation:

Department of Chemical and Biological Engineering, The University of Sheffield, Newcastle Street, Sheffield, S1 3JD, UK.



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