Determination of Germanium Species by Hydride Generation Atomic Absorption Spectrometry: Comparison of Atomizers Based on Diffusion Flame, Heated Quartz Tube, and Dielectric Barrier Discharge Plasma

Abstract

Atomization of three volatile germanium species including germanium hydride (GeH4) and its two methyl-substituted analogues -monomethyl germanium hydride (CH3GeH3) and dimethyl germanium hydride ((CH3)2GeH2) for their detection by atomic absorption spectrometry after hydride generation was comprehensively investigated. Three types of hydride atomizers based on diffusion flame (DF), multiple microflame quartz tube atomizer (MMQTA) and dielectric barrier discharge (DBD) were optimized for atomization of Ge species. In MMQTA, the supply of air and the use of gas phase dryer are the crucial parameters affecting the sensitivity. The presence of the dryer is essential also for DBD atomizer. Sensitivity was quantified under optimized conditions reaching around 2 ms ng -1 Ge in DF and 3 ms ng -1 Ge in MMQTA atomizers, respectively. The highest sensitivity of 10 ms ng -1 Ge was observed in DBD. When compared to other hydride forming elements the sensitivity observed for Ge species is two orders of magnitude worse in MMQTA, 10-50 times lower in DBD and 5 times worse in DF. In given atomizer type, the sensitivity is comparable for all three Ge species indicating the same atomization efficiency. The fraction of Ge deposited in the DBD and MMQTA atomizers, respectively, after atomization of GeH4 was quantified to 80%. Fast decay of free Ge atoms and their deposition at the inner walls of the atomizer might explain low sensitivity observed for Ge determination by atomic absorption spectrometry. Effect of L-Cysteine (L-Cys) addition to liquid standards on response of Ge species was also investigated.