Cyanide Reaction with Ninhydrin: Elucidation of Reaction and Interference Mechanisms

Abstract

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 1 H 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.

A Study on Ninhydrin Reaction with Weak Acid Dissociable Cyanide and Its Application for Toxic Cyanide Determination

“…One-step protocol, firstly described by Drochioiu [5], was based on the reaction between cyanide and ninhydrin in 2% sodium carbonate solution at ambient conditions and monitoring the absorbance of the obtained red solution at 485 nm. In sodium carbonate medium cyanide reacted with ninhydrin forming а red colored ninhydrin-cyanide adduct: 2-cyano-1,2,3-trihydroxy-2H indene [16]. Two-step protocol, firstly described by Nagaraja, Kumar, Yathiraja, and Prakash [6], was based on: firstly, formations of a red colored ninhydrin-cyanide adduct in sodium carbonate media, and secondly, formation of blue colored compound upon addition of sodium hydroxide.…”

“…Ninhydrin-cyanide reaction was proved to be strongly interfered by mercury (II), cooper (II) and silver (I), and at less extent by Ni 2+ , Zn 2+ and Cd 2+ [16,17]. However, a possible implementation of ninhydrin reagent for complex cyanide determination was supposed based on following facts: (1) cyanide bounded in complexes with Hg(II); Cu(I) and Ag(I) is 2-4 times more than the metal ion and respectively the equilibrium concentration of cyanide is higher than metal ion concentration; (2) in cooper-cyanide complex Cu(I) is involved and its reaction with ninhydrin has not been studied; (3) two competing reactions could be supposed metal-ninhydrin and cyanide-ninhydrin and difference in the reaction rates could be explored.…”

The development of smart screening technology kit (SST-Kit) for sorting cassava cultivars based on cyanide analysis

“…The intensity of the complex formed in the reaction is proportional to the concentration of cyanide (Nagaraja et al, 2002). In the previous work performed by Drochioiu et al (2004), cyanide analysis was analysed based on the presence of blue color or purple color regarding the hydrindantin formation (2-cyano-1,2,3-trihydroxy-2H indene). This method was succesfully developed because the interference, such as copper, silver, and mercury ions, was elucidated.…”

Ninhydrin-based spectrophotometric assays of trace cyanide

“…Although the reaction of ninhydrin with cyanides was investigated by Bruice and Richards in 1958, 21 it was applied in analytical procedures only recently by two independent research groups. [22][23][24] Some cyanide assays 22,23 have been based on reaction of ninhydrin with cyanides in carbonate medium and spectrophotometric detection of the colored product (2-cyano-1,2,3-trihydroxy-2H indene) around 510 nm. Nagaraja proposed a two-steps protocol: the first step was identical to that based on 510 nm reading, 23 while the second step involved alkalization of the reaction product to pH values >12, resulting in a bathochromic shift of the λ max toward 590 nm.…”