Mechanisms of chemical vapor generation by aqueous boranes for trace element analysis. Twenty years of investigations

The review reports on investigations and studies that have contributed in the last 20 years (2003–2023) to the clarification of the mechanisms governing the chemical vapor generation (CVG) of hydrides and other volatile metallic species using aqueous phase derivatization with tetrahydridoborate (1-)(THB) and amine boranes, which is widely used in determination and speciation analysis of trace elements by atomic optical and mass spectrometry. The discussion begins with the early investigations leading to definition of the mechanism of hydrolysis of aqueous THB and that of reaction conditions. The new knowledge represents important achievements for the clarification of controversial aspects that plagued CVG for more than 35 years and stimulated further studies which are discussed in detail. They concern with the mechanism of hydrolysis of amine boranes, the mechanism of interferences, the role played by chemical additives and the definition of more general reaction models for CVG, which are valid for both analytical and non-analytical reaction conditions. The latest developments and the analytical applications of the new knowledge to trace element analysis are discussed.