IUPAC

Clarification of controversial aspects related to formation of trace element hydrides/volatile metals species using aqueous phase reaction by borane complexes as derivatization reagents.

Aqueous phase chemical vapor generation (CVG) by borane complex derivatization is one of the most powerful and worldwide employed method for determination and speciation of trace and ultratrace elements Ge, Sn, Pb, As, Sb, Bi, Se, Te, Hg, Cd and, more recently also several transition and noble metal, coupled with atomic spectrometric techniques.

Thousands of research papers and many regulated analytical methods are based on CVG. However, since its first application, more than 35 years ago, the application and validation of CVG to many different analytical targets has been the prevailing aspect, while only limited efforts has been dedicated to clarification of mechanistic aspects. Analytical CVG it is still dominated by erroneous concepts (as for example the nascent hydrogen theory) which has been disseminated and consolidated in the analytical scientific community in the course of many years. As a consequence, the approach to CVG remains quite empirical, which hinders the possibility of further development. A rationalization of the field, based on more rigorous scientific approach appears to be necessary, and it could be also an impulse for further development in CVG.

In the last decade significant efforts have been dedicated to experiments and literature survey devoted to clarification of the mechanism of hydrolysis of tetrahydroborate(III) and other borane complexes, the mechanism of generation of volatile hydrides (AsH₃, Me₂AsH, MeAsH₂, SbH₃, BiH₃, GeH₄ and SnH₄) and unknown or not yet identified volatile species of transition and noble metals. The collected evidences give a solid base for the rationalization of the mechanism involved in CVG techniques.

> project announcement published in Chem. Int. 30(3) 2008

> October 2008 report update (pdf file - 17KB)

> Nov 2008: two related short papers have been published on Analytical and Bionalytical Chemistry:
- J. Mejia, A. D’Ulivo, Nascent Hydrogen Challenge, Analytical & Bioanalytical Chemistry, 2008, 391, 1475-1476. (doi: 10.1007/s00216-008-2143-4)
- J. Meija, A. D’Ulivo, Solution to Nascent Hydrogen Challenge, Analytical & Bioanalytical Chemistry, 2008, 392, 771-772. (doi: 10.1007/s00216-008-2356-6)
The aim of these papers is to put some light on the wrong concept of the “nascent hydrogen”, which is based on the results of deuterium labelled experiments, published about 45 years ago, but they had never considered by analytical chemistry community.
One more paper discussing in more depth on the same concept is in preparation for an educational journal.

Moreover, a session dedicated to the project has been organized at 10th Rio Symposium on Atomic Spectrometry, Salvador, Brazil, 7-12 Sep 2008. The preliminary outputs were presented in an invited lecture by A. D’Ulivo, “Chemical vapour generation. Towards the clarification of the most critical and controversial aspects”; book of Abstract IL-29, p.76. (www.10riosymposium.ufba.br)
Another presentation by A. D’Ulivo has been an invited lecture titled “Mechanisms of chemical vapour generation by tetrahydroborate(III) derivatization”, at the 6th Aegean Analytical Chemistry Days, 9-12 October 2008, Denizli, Turkey; see book of abstract, IL 07, p. 50. (http://aacd2008.pamukkale.edu.tr)

All the milestones relevant to the completion of the IUPAC technical report have been fulfilled and the internal review process should be finished before March 2009. Then, the technical report should be ready for external reviewers.

A final meeting of the Project will be held in Budapest in the occasion of Colloquium Spectroscopicum Internationale XXXVI (29 August – 3 September 2009). A special session, dedicated to mechanistic aspect of vapour generation, will be organized. In that occasion several lectures illustrating the final results of the IUPAC Project will be held by chairman and by some of the members of the task group.