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-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.
Drochioiu
Gabi
G
Organic Chemistry and Biochemistry Department, Al I Cuza University of Iasi, 11 Carol I, Iasi-700506, Romania. gabidr@uaic.ro
Mangalagiu
Ionel
I
Avram
Ecaterina
E
Popa
Karin
K
Dirtu
Alin Constantin
AC
Druta
Ioan
I
D003486:Cyanides / Q000737:chemistry*; D015394:Molecular Structure; D009555:Ninhydrin / Q000737:chemistry*
D003486:Cyanides; D009555:Ninhydrin