Mechanisms involved in chemical vapor generation by aqueous tetra hydroborate(III) derivatization - Role of hexacyanoferrate(III) in plumbane generation

The role played by K(3)Fe(CN)(6) (0.08 or 1.5 g l(-1)) in producing strong enhancement factors in the generation efficiency 0fplUmbane in the reaction of NaBH4 (10 or 40 g l(-1)) with Pb(II) (50 mu g l(-1)) in 0.1 IM HCl solution, was investigated by using continuous flow chemical vapor generation coupled with atomic fluorescence spectrometry (CF-CVG-AFS). Different mixing sequences and reaction times of reagents were tested using different chernifold setups. Part of CF-CVG-AFS experiments were performed using the on-line, delayed addition of Pb(II) to a K(3)Fe(CN)(6)+ NaBH(4) reaction mixture. Kinetic calculations estimating the concentration of K(3)Fe(CN)(6) remaining in the K(3)Fe(CN)(6)+ NaBH(4) reaction mixture before it merged with Pb(II) solution were also performed. Batch experiments measuring the amount of hydrogen evolved (pressure of H(2) vs time) and pH variation during K(3)Fe(CN)(6)+ NaBH(4)+ HCl reaction were performed in order to have a correct estimation ofthe concentration of K(3)Fe(CN)(6) remaining in the reaction system. The comparison of CF-CVG-AFS experiments with kinetic calculations indicates that strong enhancement factors of plumbane generation can be obtained without any interaction of K(3)Fe(CN)(6)+ NaBH(4) with Pb(II). The key role of K3Fe(CN)r is recognized in its reaction with NaBH4 to give "special" borane complex intermediates, which are highly effective in the generation of plumbane from Pb(H). (c) 2008 Elsevier B.V. All rights reserved.