An Atomic Absorption Analysis Method for Cyanide

Abstract

An atomic absorption analysis procedure for cyanide has been developed. The procedure is based upon the solubilization of copper(II) from a basic copper carbonate in an alkaline medium. The amount of copper complexed by the cyanide ion is determined by atomic absorption and a calibration curve is constructed concurrently. The stoichiometry of the cyanide-copper complex is 3:1, implying formation of the complex ion Cu(CN)^? ₃, with no formation of CuCN observed at the low concentration of cyanide used. The method is used primarily for analyzing low levels of cyanide; the sensitivity of the method extending down to 2.0 × 10^?5 M CN^?. The most likely interference, iron, is considered. Finally, recovery of cyanide from spiked samples is demonstrated.     

Oxidation of the cyanide ion at a platinum electrode studied by polarization modulation infrared reflection absorption spectroscopy

The anodic oxidation of the cyanide ion at a platinum electrode in aqueous solution was observed by polarization modulation infrared reflection absorption spectroscopy(PM IRRAS). The cyanide ion was adsorbed on the electrode surface in the potential region more negative than 0.4 V (versus Ag/AgCl). In the more positive region (> 0.4 V ), the adsorbed cyanide ion was oxidized to form the cyanate ion. Cyanogen was not detected during the oxidation reactions; this suggests direct electrochemical formation of the cyanate ion.     

FLAVIN-PHOTOREDUCTION BY CYANIDE: NUCLEOPHILIC ADDITION IN THE EXCITED TRIPLET STATE

Abstract— Flavin photochemistry as well as biochemistry consists of competitive 1e⁻ - and 2e⁻ -reduction pathways, depending on the nature of the substrate. We show that cyanide ion is a photosubstrate which suppresses 1e⁻-oxidoreduction and leads to exclusive formation of 6- and 9-cyano-1,5-dihydroflavin. The photoreduction mechanism is thus revealed as a nucleophilic addition of cyanide ion at the excited flavin triplet. Preparative photochemistry and isolation and characterization of cyanoflavins have been done, as well as thorough mechanistic studies by conventional flash photolysis. In contrast, nitrite ion is shown to be a normal photosubstrate for flavins leading to exclusive 1e⁻ -transfer followed by back donation.     

A Chemodosimetric Probe Based on a Conjugated Oxidized Bis‐Indolyl System for Selective Naked‐Eye Sensing of Cyanide Ions in Water

A new bis‐indolyl‐based colorimetric probe has been synthesized. This allows a Michael‐type adduct formation for the detection of cyanide ions. The probe shows a remarkable color change from red to colorless upon addition of the cyanide ions in pure water. The cyanide ion reacts with the probe and removes the conjugation of the bis‐indolyl moiety of the probe with that of the 4‐substituted aromatic ring. This renders the probe colorless. The mechanism of the reaction of the probe with the cyanide ion was established by using ¹H and ¹³C NMR spectroscopy, mass spectrometry, and kinetic studies.     

Addition of the cyanide ion to cyclopentadienyliron complexes of arenes containing an electron-withdrawing substituent

Reactions of cyclopentadienyliron (CpFe) complexes of arenes containing an electron-withdrawing substituent with NaCN in DMF resulted in a regiospecific addition of the cyanide ion at a position ortho to the substituent, giving rise to CpFe complexes of cyanocyclohexadienyl systems. For example, the addition of the cyanide ion to η⁶-nitrobenzene-η⁵-cyclopentadienyliron hexafluorophosphate (Ia) gave the neutral complex, 1-5-η⁵-exo-6-cyano-1-nitrocyclohexadienyl-η⁵-cyclopentadienyliron (IIa). Similar cyanide additions also took place with the CpFe complexes of benzophenone and of methyl benzoate. Reactions with η⁶-anthraquinone, xanthone, thioxanthone, or thioxanthone-10,10-dioxide-η⁵-cyclopentadienyliron hexafluorophosphate (IIIa, IIIb, IIIc or IIId, respectively) resulted in the addition of the cyanide ion solely to C(1), a position ortho to the keto substituent; for example, from IIIa, the adduct was 2,3,4,4a,9a-η⁵,-exo-1-cyano-1H-anthraquinone-η⁵-cyclopentadienyliron (IVa). With the CpFe complex of fluorenone (V), however, a 3/1 mixture of products was obtained, arising from cyanide additions to C(1) and C(4a), both positions being ortho to the keto substituent in V. A possible explanation is suggested for the failure of the cyanide ion adding to C(4a) in reactions with IIIa to IIId.     

An Efficient Probe for Rapid Detection of Cyanide in Water at Parts per Billion Levels and Naked‐Eye Detection of Endogenous Cyanide

A new molecular probe based on an oxidized bis‐indolyl skeleton has been developed for rapid and sensitive visual detection of cyanide ions in water and also for the detection of endogenously bound cyanide. The probe allows the “naked‐eye” detection of cyanide ions in water with a visual color change from red to yellow (Δλ_max=80 nm) with the immediate addition of the probe. It shows high selectivity towards the cyanide ion without any interference from other anions. The detection of cyanide by the probe is ratiometric, thus making the detection quantitative. A Michael‐type addition reaction of the probe with the cyanide ion takes place during this chemodosimetric process. In water, the detection limit was found to be at the parts per million level, which improved drastically when a neutral micellar medium was employed, and it showed a parts‐per‐billion‐level detection, which is even 25‐fold lower than the permitted limits of cyanide in water. The probe could also efficiently detect the endogenously bound cyanide in cassava (a staple food) with a clear visual color change without requiring any sample pretreatment and/or any special reaction conditions such as pH or temperature. Thus the probe could serve as a practical naked‐eye probe for “in‐field” experiments without requiring any sophisticated instruments.     

Kinetic spectrophotometric determination of nanogram amounts of cyanide

A sensitive kinetic method for determination of nanogram amounts of cyanide is reported. It is based on the measurement of the induction period imposed by cyanide on the copper(II)-catalysed oxidation of 3-hydroxybenzaldehyde azine (3-OHBAA) by potassium peroxydisulphate. Kinetic data are recorded spectrophotometrically at 465 nm, the maximum absorption wavelength of the oxidation product of 3-OHBAA. From the kinetic study and other experimental tests it may be concluded that the cyanide ion undergoes copper(II)-catalysed oxidation during the induction period. The calibration plot is linear in the range 150-600 ng/ml cyanide and the detection limit is 50 ng/ml. The precision of the method, expressed as the relative standard deviation, is 3.2% for 350 ng/ml cyanide. Good recoveries are obtained in applying the method to analysis for cyanide in water samples.     

Coumarin-Cu(II) ensemble-based cyanide sensing chemodosimeter

An "ensemble"-based chemodosimeter 1-Cu(II) for cyanide detection is reported. 1-Cu(II) can recognize a cyanide ion over other anionic species to show a marked fluorescence enhancement under aqueous conditions. "Off-on" fluorescence change of 1-Cu(II) is proceeded by addition of cyanide, which induces decomplexation of the Cu(II) ion from nonfluorescent 1 followed by hydrolytic cleavage of the resulted Schiff base to give a strongly fluorescent coumarinaldehyde (2). The selective detection of cyanide with 1-Cu(II) for biological application was also performed in HepG2 cells.     

Colorimetric probes based on anthraimidazolediones for selective sensing of fluoride and cyanide ion via intramolecular charge transfer

Probes based on anthra[1,2-d]imidazole-6,11-dione were designed and synthesized for selective ion sensing. Each probe acted as strong colorimetric sensors for fluoride and cyanide ions and exhibited intramolecular charge transfer (ICT) band, which showed significant red-shifts after addition of either the F(-) or CN(-) ion. One of the probes (2) showed selective colorimetric sensing for both cyanide and fluoride ions. In organic medium, 2 showed selective color change with fluoride and cyanide, whereas in aqueous organic medium it showed a ratiometric response selectively for cyanide ion.     

Mimicking a Receptor for Cyanide Ion Based on Ion Imprinting and Its Applications in Potential Transduction

Using the strategy of template polymerization, a presynthesized specific metal‐complexing polymer (poly(methacryloylhistidine‐Ni(II)‐CN^?), Ni‐CN/IP) has been specifically used to recognize cyanide ion. As described previously, nickel(II)‐methacryloylhistidine dihydrate complex monomer was synthesized and reacted with KCN to produce the monomer‐template complex. This monomer‐template complex phase was polymerized in a dispersion medium. After polymerization, the template (CN^?) was removed from the Ni‐CN/IP, producing CN^? ion imprinted metal‐chelate polymer. The synthesized ion imprinted polymer is examined as a novel potential cyanide selective ionophore in polymeric membrane type ion selective electrodes. Membranes formulated with Ni‐CN/IP are shown to exhibit enhanced potentiometric selectivity for cyanide over more lipophilic anions including perchlorate, iodide, and thiocyanate. Addition of lipophilic cationic sites into the organic membranes enhanced the response and selectivity towards CN^? ion, while addition of lipophilic anionic sites deteriorated the response but enhanced the selectivity, indicating that the Ni‐CN/IP particles behaves via the so‐called “mixed‐mode” response mechanism. The fabricated sensors possessed good performance characteristics, in terms of life span, selectivity for CN^? ion over a wide range of other interfering anions, fast response, stability and high reproducibility. Applications for direct determination of cyanide ion in hazardous wastes using the proposed sensors showed good correlation with data obtained using commercial solid state cyanide electrode, with no significant difference in the t‐test values with 95 % confidence level. An F‐test revealed that the standard deviations of the replicate sample measurements obtained by the two methods were not significantly different.     

Indirect determination of free cyanide in industrial waste effluent by atomic absorption spectrometry

An indirect method is described for the determination of free cyanide in industrial waste effluent samples by atomic absorption spectrometry (AAS). In an alkaline medium, cyanide forms a stable complex species [Cu(BPTC)(CN)] (BPTC = 2-benzoylpyridine thiosemicarbazone), which can be extracted into a mixture of isobutyl methyl ketone-isopentyl alcohol (7 + 1) with an efficiency of greater than 98.5%. The extract can be analysed directly for copper (and hence indirectly for cyanide) by flame AAS. The calibration graph is linear up to 5.7 micrograms of cyanide per millilitre of solvent mixture and the limit of detection is 4.8 ng ml-1. A large number of foreign ions were found not to interfere with the proposed method.     

Systemes de strecker et apparentes—II : Mécanisme de formation en solution aqueuse des α-alcoylaminoisobutyronitrile à partir d'acétone,d'acide cyanhydrique et d'ammoniaque,methyl ou diméthylamine

The formation of N-substituted tertiary α-aminosobutyronitriles from acetone, alkali, cyanide amine, has been studied in aqueous solutions of pH 8–12. Competition between the cyanide and amine for acetone first favours cyanohydrin formation. The α-aminonitrile is then slowly formed. The kinetic study of the reaction, as a function of cyanide concentration, shows two successive slow steps. In the presence of excess cyanide, the first step, limiting the reaction rate, is formation of intermediate imine. This is catalysed neither by OH^? or H₃O⁺ and depends only on the concentration of amine in basic form. The mechanism of the second step, the imine forming the α-aminonitrile, is discussed in terms of acid catalysed addition of the cyanide ion to the imine.     

Indirect Determination of Cyanide by Atomic Absorption Spectrometry

Abstract

Two methods for determination of cyanide by atomic absorption spectrometry (AAS) are developed. Both methods are based on the formation of an ion association compound between a metal complex, (Ag(CN)₂ ^? or Cu(CN)₃ ^2-), and a quaternary ammonium ion (benzyldimethylhexadecylammonium ion). The ion association compound is extracted into isomethylbutylketone (IBMK) and the metal is determined by AAS directly in extract. The method based on the formation of silver cyanide complex provides a reproducibility of 2.5%, a recovery of 99% and a detection limit of 1.7 μg/L while the method based on the formation of copper complex gives a reproducibility of 6%, a recovery of 93% and a detection limit of 0.6 μg/L. Several foreign ions were studied: the method based on the formation of Ag(CN)₂ ^? presents minor interferences.     

Rational design of a dual chemosensor for cyanide anion sensing based on dicyanovinyl-substituted benzofurazan

A dicyanovinyl-substituted benzofurazan derivative (C1) was prepared as an efficient ratiometric chemosensor for cyanide anion detection in aqueous acetonitrile solution. Mechanism studies suggested that the nucleophilic addition of cyanide to the α-position of the dicyanovinyl group blocked the ICT progress of C1 and induced remarkable emission and absorption shift.     

Analytical chemistry of unusual oxidation states: the polarography of vanadium(IV) in cyanide medium

The polarographic reduction wave for vanadium(IV) in cyanide medium has been studied and the effect of cyanide concentration on the diffusion current and half-wave potential has been interpreted, using the theory of irreversible but diffusion-controlled reduction. Coulometric experiments suggest a two-electron transfer, and the shift of half-wave potential corresponds to the addition of one cyanide ion during the reduction step. The proportionality of wave-height to vanadium concentration in the used alkaline cyanide medium indicates a possible analytical unity. The half-wave potential is about -1.1 V.     

THE VISUAL PIGMENT CYANIDE EFFECT

The visual pigment of the Tokay gecko (Gekko gekko) with its in situ absorption maximum at 521 nm has its spectral position at 500 to 505 nm when chloride-deficient digitonin is used for the extraction. In this case the addition of chloride or bromide to the extract restores the maximum to 521 nm. This property, characteristic of gecko pigments in general, does not occur with any of the rhodopsins that have been tested. Simple salts of cyanide, a pseudohalogenoid with an ionic radius close to those of chloride and bromide and/or its hydrolysis product attacks both this gecko pigment and rhodopsins in the dark. This is seen as a slow thermal loss of photopigment if (sodium) cyanide is present at concentrations above 40 mM for the gecko pigment and 150 mM for the rhodopsins of the midshipman (Porichthys notatus) and of the frog (Rana pipiens). In all cases the loss of the photopigment is accompanied by the appearance of a spectral product with maximum absorption at about 340 nm. Cyanide addition has no effect on the photosensitivity of the native pigments and neither does it alter, as do chloride, bromide and other anions, the spectral absorbance curve. The spectral product at 340 nm also appears when the visual pigments are photolyzed in the presence of cyanide salts below the threshold concentrations given above. Incubation of digitonin-solubilized all-trans-retinal with (sodium) cyanide leads to a reaction product with absorption spectrum similar to that obtained with visual pigments under comparable conditions.(ABSTRACT TRUNCATED AT 250 WORDS)     

New spot-test for cyanide ion and cyanogen gas

A new, rapid and simple spot test has been developed for detection of both cyanide ion and cyanogen gas. The cyanogen gas must first be converted into cyanide ion by reaction with sodium hydroxide. On addition of a Cu(II) solution the cyanocuprate(I) complex formed reduces the molybdate solution to molybdenum blue.     

Direct determination of hydrogen cyanide in cigarette mainstream smoke by ion chromatography with pulsed amperometric detection

The determination of hydrogen cyanide in cigarette mainstream smoke has been achieved by ion chromatography (IC) with pulsed amperometric detection (PAD). The proposed method of totally trapping whole cigarette mainstream smoke by Cambridge filters, which are treated with sodium hydroxide/ethanol solution, possesses the advantage of fast analysis time over the widespread used solution absorption method. The possible co-existing interferents are evaluated under the optimized detection conditions and excellent recoveries of cyanide are obtained. The cyanide content of absorption solution can be directly determined by the optimized IC-PAD method without any pretreatments. The linear range is 0.0147-2.45 μg/mL with R2 value of 0.9997. The limit of the detection is 3 μg/L for a 25 μL injection loop. The overall relative standard deviation of the method is less than 5.20% and the recovery range from 94.3% to 101.0%. The results obtained from the developed method are in good agreement with that of continuous flow analyzer (CFA) method.     

A simple dual-channel sensor for detecting cyanide in water with high selectivity and sensitivity

Taking advantage of the special nucleophilicity of cyanide, a new simple colorimetric chemosensor has been synthesised. This allows a deprotonation reaction to monitoring the cyanide. With the addition of CN^? to the chemosensor aqueous solution, which could induce a change in the solution colour from yellowish to deep yellow, while no colour change could be observed in the presence of other hackneyed anions, by which CN^? can be distinguished from other anions immediate with the naked eye. At the same time, a fluorescence quenching was implemented upon adding cyanide into the chemosensor aqueous solution. The absorption spectra detection limits of the chemosensor for cyanide was 5.35 × 10^?8 M and the fluorescence spectra detection limit was 2.63 × 10^?8 M. The cyanide test strips based on the chemosensor could serve as a convenient cyanide test kits. Furthermore, the chemosensor was successfully applied to detect cyanide in sprouting potatoes.     

Elimination of the interfering effects of ligands in the determination of cobalt by atomic absorption spectrometry

In atomic absorption spectrometric determinations of cobalt(II) and cobalt(III), the interfering effects of different complex-forming substances can be completely eliminated by addition of excess of cyanide. Cyanide has a double role: first, it forms very stable cyano complexes, so that the cobalt species reaching the flame will normally be independent of the original composition of the solution; secondly, the high excess of cyanide produces favourable physical and chemical conditions for cobalt atomization.