Effect of Additives on the Chemical Vapour Generation of Bismuthane by Tetrahydroborate(III) derivatization

The effect of mM concentrations of K3[Fe (CN)6], Fe(III), Mo(VI), KSCN and KMnO4 on the generation of BiH3 by the reaction of 0.2-10 ?g ml-1 Bi(III) with 0.2 M tetrahydroborate(III) at 1 M acidity (HCl or HNO3) was investigated. Chemical vapour generation (CVG) of BiH3 was investigated by atomic absorption spectrometry using a continuous flow reaction system (CF-CVG-AAS) and different mixing sequences and reagent reaction times. Gas chromatography-mass spectrometry (GC-MS) was employed in batch generation experiments with NaBD4. In the absence of additives, the formation of Bi0 at high concentrations of Bi(III) caused rollover of calibration curves and limited the linear range to less than 1 ?g ml-1 Bi(III). In the presence of additives, the formation of Bi0 was not observed and the linear range was increased to 5 ?g ml-1 of Bi(III) while rollover was completely removed. GC-MS experiments indicated that the presence of additives did not affect the direct transfer of H from boron to bismuth. Experiments with CF-CVG-AAS and different mixing sequences and reagent reaction times suggest that additives act by preventing the formation of Bi0 through the formation of reaction intermediates which evolve towards the formation of BiH3 at elevated Bi(III)/NaBH4 ratios.