Cyanide Reaction with Ninhydrin: Elucidation of Reaction and Interference Mechanisms

A new sensitive spectrophotometric method has recently been developed for the trace determination of cyanide with ninhydrin. Cyanide ion was supposed to act as a specific base catalyst. Nevertheless, this paper demonstrates that the reported assay is based on a novel reaction of cyanide with 2,2-dih...

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Bibliographic Details
Published in:Analytical Sciences 2004, Vol.20(10), pp.1443-1447
Main Authors: DROCHIOIU, Gabi, MANGALAGIU, Ionel, AVRAM, Ecaterina, POPA, Karin, DIRTU, Alin Constantin, DRUTA, Ioan
Format: Article
Language:English
Subjects:
Cyanides - chemistry
Molecular Structure
Ninhydrin - chemistry
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Summary:A new sensitive spectrophotometric method has recently been developed for the trace determination of cyanide with ninhydrin. Cyanide ion was supposed to act as a specific base catalyst. Nevertheless, this paper demonstrates that the reported assay is based on a novel reaction of cyanide with 2,2-dihydroxy-1,3-indanedione, which affords purple or blue colored salts of 2-cyano-1,2,3-trihydroxy-2H indene. Hydrindantin is merely an intermediary of the reaction. The formation of a stable and isolable ninhydrin-cyanide compound has been confirmed by its preparation in crystalline form. Also, it is thoroughly characterized by elemental as well as MS, IR, UV/VIS and 1H NMR analyses. The Ruhemann’s sequence of reactions of cyanide with ninhydrin has been reconsidered and an adequate mechanism of the reaction is proposed. As a consequence, the interference of oxidizers as well as copper, silver and mercury ions with the cyanide determination has been elucidated.
ISSN:0910-6340
1348-2246
DOI:10.2116/analsci.20.1443