Automated Colorimetric Method for Total Cyanide in Water and Wastewater

Abstract

An automated benzidine-pyridine method for the analysis of total cyanide is described. Cyanides are converted to cyanogen bromide by the reaction with bromine water. Cyanogen bromide reacts with benzidine in a dilute pyridine medium to form an intense red color directly proportional to the cyanide concentration. Cyanide often is found complexed with metals. Complex iron cyanides such as ferrocyanide or ferricyanide are difficult to decompose, but the conversion is hastened with mercuric chloride and magnesium chloride in a modified Serfass distillation.¹

Hydrogen cyanide is readily formed and absorbed in sodium hydroxide.     

Optical detection of cyanide by palladium(II)-dithiazolopyridine probe at the parts per billion level

Abstract

The ensemble of 2,6-bis(2-chlorophenyl)dithiazolo[4,5-b:5',4'-e]pyridine 1 with Pd²⁺ ions (1?Pd²⁺) was prepared for the detection of cyanide ions (CN^¯) in 50% aqueous methanol. Among the tested metal ions, only Pd²⁺ sensitively induced the red shift of the absorption bands and the complete decrease of fluorescence emission. The detection limit toward Pd²⁺ was 2?ppb. The ensemble 1?Pd²⁺ selectively and rapidly detected a low concentration of cyanide ions by a colorimetric change (40?ppb) as well as a “turn-on” fluorescent response (5?ppb). Job’s plot revealed the complex formation with 1:1 stoichiometry. The binding and replacement mode of 1?Pd²⁺ and CN^¯ were also confirmed by ¹H NMR titrations and IR analysis. In general, a fast and selective recognition of CN^¯ is reported.     

Asensitive,Selective, and Rapid Colorimetric Method to Determine Cyanide Contamination in Containers,Capsules, and Liquids

Abstract

A new formulation of the Konig colorimetric method for cyanide is selective, has increased stability, and is sensitive to a few ppb. The formulation can be placed as a strip on the safety seals of bottles to indicate tampering, placed in a syringe and used to sample head space gas in commercial products or liquids to test for tampering, or placed in the desiccant container in bottles of capsules or tablets. Reaction with head space gas requires just a few seconds, and less than an hour is required if the cyanide must first permeate through capsules. Liquids also can be either drawn directly into the syringe, or the cyanide evolved by adding an Alka-seltzer tablet to purge the gas. Reactions are immediate. Hydrogen sulfide and ammonia which interfere with several other cyanide tests, do not interfere with this formulation. A mixture of N-chlorosuccinimide and succinimide oxidizes CN^- to CN⁺. The cyanogen ion selectively reacts with 4-phenylpyridine to form a dialdehyde, which is then coupled with either barbituric acid (red rapidly turning to blue) or 3-methyl-l-phenyl-2-pyrazolin-5-one (purple slowly turning to green black).     

Determination of Free Cyanide in Water by Released Flourescence of a Dissociated Ternary Complex

Abstract

A flourometric procedure for the analysis of free cyanide is described. The method is based on the dissociation of a ternary complex of silver-1, 10-phenanthroline-tetrabromofluorescein by cyanide to produce a fluorescent product. The fluorescence intensity is found to be directly proportional to the cyanide concentration. The method can reliably detect 0.02 μg/mL cyanide.     

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.     

A New Spectrophotometry Determination of Cyanide by Solvent Extraction as Tris-(1,10-Phenanthroline)-Iron (II)-Thiocymate

Abstract

By shaking aqueous cyanide solution with nitrobenzene contained sulfur, thiocyanate is formed and is extracted into the nitrobenzene as an ion pair of thiocyanate anion and tris-(1,10-phenanthroline)-iron(II) chelate cation. By measuring the color intensity of the organic phase at 516 nm, cyanide is determined spectrophotometrically. A linear calibration curve is obtained up to 4 × 10^?5M of cyanide in the aqueous phase.     

Coulometric Determination of Total Cyanide in Effluent and Wastewater

Abstract

A simple procedure for the determination of low levels of total cyanide in effluent samples has been developed. After distillation of the cyanide from the sample, as hydrocyanic acid, the cyanide is determined with coulometrically generated iodine using a biamperometric end point detection system. As little as 0.06mg/l total cyanide can be measured using the procedure. The method obviates the need for calibration curves and does not require special reagents.

Silver (I) was determined to be an effective catalyst for the decomposition of bound cyanides in the distillation procedure.     

A highly selective and sensitive dual-channel chemosensor for cyanide based on sulfahydrazone derivative

A colorimetric and fluorescent cyanide probe bearing naphthol and sulfahydrazone groups has been designed and synthesized. This structurally simple probe displays a rapid response and high selectivity for cyanide in DMSO/EtOH (v/v = 2:8) solution. The addition of CN^? to the sensor p-toluenesulfonyl-2-hydroxy-1-naphthylhydrazone (L3) induced a remarkable color change from pale-yellow to yellow, and green fluorescence changed to yellow. The ¹H NMR titration and DFT calculations suggested that the selective sensing process is based on a nucleophilic addition reaction of cyanide to imine. Test strips based on sensor L3 were fabricated, which could act as a convenient and efficient test kit to detect CN^? for “in-the-field” measurements.     

Analysis of Cyanide in Blood by Headspace-Isotope-Dilution-GC-MS

Abstract

An uncomplicated, rapid, automated procedure for the analysis of low cyanide concentrations in whole blood is reported. The analysis was performed by headspace gas chromatography and mass spectrometry in the (¹H¹²C¹⁴N) and m/z 29 (¹H¹³C¹⁵N). Carryover from cyanide adsorption onto the surface of the needle was prevented by developing a new method that enabled automated flushing of the needle in between each cyanide analysis. Results were compared of ordinary calibrations and those of isotope dilutions. The total time of analysis was 18 min for a single cyanide analysis.     

Continuous Determination of Free Cyanide by Means of Membrane Diffusion of Gaseous HCN and An Electrode Indicator Technique

Abstract

A continuous measurement system for free cyanide has been developed based on the principle of diffusion across a gas-permeable membrane to affect the separation of hydrogen cyanide from the acidified sample solution. The cyanide absorbed in the alkaline indicator solution is subsequently analyzed by an indirect technique using a silver ion-selective electrode. In the concentration range of 30 to 400 μg CN^?/L, the accuracy and precision of this method is approximately two percent. The detection limit of this system is approximately 0.5 μg CN^?/L.     

Didodecyldimethylammonium Bromide Bilayer Vesicle-Catalyzed and Uranine-Sensitized Chemiluminescence for Determination of Free Cyanide at Picogram Levels by Flow Injection Method

Abstract

A novel chemiluminescence system, didodecyldimethylammonium bromide-uranine-sodium hydroxide, is described for the determination of ultratraces of free cyanide by flow injection method. Organized surfactant assemblies(bilayer vesicles) incorporated with a sensitizer (uranine) permit the determination of free cyanide very selectively with a limit of determination of 1 pg (20-μ1 sample injection). Sulfide, the strongest CL inducer after free cyanide, provides a signal 0.1 % of that for free cyanide.     

Cyanide by Prussian Blue Spot Formation

Abstract

A simple quantitative test for cyanide is described. Cyanide is released as the hydrocyanic acid and conducted through a prepared disk to form a prussian blue spot. This spot is visually or instrumentally compared to standard spots. Two μg of cyanide can be detected by this method.     

Spectrophotometric determination of cyanide by chromogenic disulfide in water using micellar catalysis

A spectrophotometric method is developed for the determination of cyanide in aqueous solutions using chromogenic disulfide 4,4′-2bis(1-hydroxy-3,6-disulfo-8-chloro-2-naphthylazo)diphenyldisulfide (BAS-chlorine) in the presence of cetyltrimethylammonium chloride (CTMAC). The use of CTMAC allows diminishing the limit of detection for the spectrophotometric determination of cyanide to (7.2 ± 0.3) ng/mL (p = 0.95, n = 5, RSD = 29%).     

Complex Formation Between Hydroxy Naphthol Blue and First Row Transition Metal Cyanide Complexes

Abstract

It has been found that cyanide complexes of first row transition metal elements exhibit enhanced binding to hydroxy naphthol blue (HNB) relative to the binding of corresponding aquo-ions. HNB forms a 2:1 complex with Fe³⁺ and Cu²⁺ cyanides, and 1:1 complexes with all other transition metal cyanide complexes studied; formation constants have been calculated from the spectrophotometric data in each case. It is possible to use HNB as a spectrophotometric reagent for transition metal cyanide complexes, lower limits of detection being determined for each complex.     

Controllable and reversible proton transfer for inorganic cyanide visual sensing based on the deprotonation of azo-phenolic hydroxyl group

ABSTRACT

Methods for optical detection of inorganic cyanide based on the single molecule sensor with high selectivity and sensitivity have attracted increasing interest recently due to the high toxicity of cyanide ions. In this work, a visual sensor (S1) containing both imidazole NH and azo-phenolic OH was synthesised and characterised. The spectral experimental data indicated that protic aqueous solution facilitated enhancing the selectivity of cyanide ions with the nanomolar-level detection limit in semi-aqueous solution. The visual sensing mechanism arising from the deprotonation of azo-phenolic OH and the enhancement of intramolecular charge transfer could be clearly demonstrated by titration experiments of ¹H NMR, HR MS and energy changes between the HOMO?LUMO band gaps. Furthermore, the reversibility and reusability of S1 upon alternating addition of CN^? and H⁺ were studied.     

A Modified Method for Measuring Cyanide in Biological Specimens

Abstract

The use of cyanide generating substances for medical, home and business applications has necessitated the need for measuring sublethal levels of this substance because of the potential of inadvertent cyanide poisoning. The method we propose provides a means for more accurate recovery at an increased rate of reaction there by making its sensitivity more conducive to the measurement of minute quantities of cyanide.     

Coulometric Titration of Free Cyanide with Electrogenerated Hypobromite

Abstract

A rapid and sensitive method is described for the direct determination of cyanide by coulometric titration with electrogenerated hypobromite. A biamperometric end point was utilized. From 0.498 – 9.980 ueq of cyanide were analyzed with an average error of 0.36% and an average standard deviation of 0.045.     

Use of an Aqueous Micellar Medium to Improve the Spectrophotometry Determination of Cyanide Ion with 5,5′-Dithiobis(2-Nitrobenzoic Acid)

Abstract

The spectrophotometric method for the determination of cyanide, which is based on the reaction of cyanide ion with 5,5′-dithiobis(2-nitrobenzoic acid) to displace the corresponding absorbing thiol anion, has been reinvestigated using an aqueous cetyltrimethylammonium bromide micellar reaction medium. The rate of the analytical reaction is increased considerably in the presence of the cationic surfactant. Thus, the time required for the spectrophotometric determination of cyanide ion in the 0.18 – 2.80 μg/ml range using this procedure is decreased from 25 minutes to 1 – 3 minutes.     

False Detection of Cyanide Ion in Photographic Processing Waste Solutions Using Standardized Reference Methods

Abstract

Although cyanide compounds are not incorporated in photographic processing solutions, false detection of cyanide ion is often encountered during the determination of total cyanide by various standardized methods such as ISO, ANSI and JIS. Various organic compounds and nitrogen compounds in the processing solutions were examined because of this false detection. The results suggest that hydrogen cyanide is formed by a reaction between these compounds during the distillation process for the separation of total cyanide, even though ISO, ANSI and JIS were used. The results support the following three mechanisms of cyanide formation involved in the process: (1) Hydroxylammonium salts reacts with another ingredient, formaldehyde, to form formaldoxime, which then decomposes to HCN. (2) Hydroxylammonium is oxidized by air to form nitrite ion, which subsequently reacts with organic compounds such as aminocarboxylic acids and aromatic amines (the colour-developing agent) to form HCN. (3) Potassium permanganate oxidizes aromatic amines to form HCN.     

Determination of Cyanide Ion by Derivatization-Gas Chromatography

Abstract

A new gas chromatographic method is described for the determination of cyanide ion in water. Cyanide is converted to benzonitrile by reaction with aniline, sodium nitrite, and copper(II) sulfate. The resulting benzonitrile is extracted into chloroform and determined by gas chromatography with a flame ionization detector. The influences of several ions which may coexist with cyanide on this gas chromatographic method were investigated briefly.