Cyanide, quantitative determination

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

As esters the alkyl halides are hydrolysed by alkalis to alcohols and salts of halogen acids. They are converted by nascent hydrogen into hydrocarbons, by ammonia into amines, by alkoxides into ethers, by alkali hydrogen sulphides into mercaptans, by potassium cyanide into nitriles, and by sodium acetate into acetic esters. (Formulate these reactions.) The alkyl halides are practically insoluble in water but are, on the other hand, miscible with organic solvents. As a consequence of the great affinity of iodine for silver, the alkyl iodides are almost instantaneously decomposed by aqueous-alcoholic silver nitrate solution, and so yield silver iodide and alcohol. The important method of Ziesel for the quantitative determination of alkyl groups combined in the form of ethers, depends on this property (cf. p. 80). 

Quantitative Determination.— Dissolve. 1 gm. of pnlits.sinin cyanide in water and dilute to IOO cc. Dilute 10 ee, of this solution with 90 cc. of water, add a grannie of sodium chloride, and titrate with dcciriormal silver nitrate solid inn until a permanent, whitish turbidity appears. 

Quantitative Determination.— Dissolve 1 giii. of pola.s.siniii cyanide in water and rlihiU. to 100 cc. Diluh 10 c( . of Ihi.s solution with 90 cc. of water, juld a grauuki of sodium iddoridi, and titrate with decinornial silver nitrate solution uiilil a permanent, whitish turbidity appoans. 

The cyanogen halides can be detected at trace levels using gas chromatography with electron-capture detection. Thiocyanate can be quantitatively determined in the presence of cyanide by the addition of an excess of formaldehyde which converts the cyanide ion to the unreactive cyanohydrin. 

Taylor, M.J. and J.F. Graham Simultaneous quantitative determination of formaldehyde and hydrogen cyanide in cigarette smoke using a simple solid trapping system CORESTA 1986 Symp., Taormina, Italy, CORESTA Inf. Bull., Spec. Edition 1986 Paper ST09, 104-105. 

Wet chemistry Procedures that involve distillations, colorimetric determinations, and titrimetric measurements. Examples of analytes that are routinely quantitatively determined by wet chemical methods include cyanides, methylene blue active surfactants, biological and chemical oxygen demands, abbreviated BOD, and COD. 

The identification and quantitative determination of decomposition products can be carried out by any of the appropriate techniques of classical and modern analytical chemistry. Carbon monoxide, carbon dioxide, water, hydrogen chloride, hydrogen cyanide, sulphur dioxide, and other inorganics are still analyzed by the conventional methods. The organics such as hydrocarbons, alcohols, aldehydes, ketones, etc. are usually separated and determined by gas chromatography. 

Brinker, a. M. and D. S. Seigler, Methods for the detection and quantitative determination of cyanide in plant materials, Phyto-chem. Bull., 21, 24-31 (1989). 

In the former, it gives precipitates with halides (except the fluoride), cyanides, thiocyanates, chromates(VI), phosphate(V), and most ions of organic acids. The silver salts of organic acids are obtained as white precipitates on adding silver nitrate to a neutral solution of the acid. These silver salts on ignition leave silver. When this reaction is carried out quantitatively, it provides a means of determining the basicity of the acid... 

The method may also be applied to the analysis of silver halides by dissolution in excess of cyanide solution and back-titration with standard silver nitrate. It can also be utilised indirectly for the determination of several metals, notably nickel, cobalt, and zinc, which form stable stoichiometric complexes with cyanide ion. Thus if a Ni(II) salt in ammoniacal solution is heated with excess of cyanide ion, the [Ni(CN)4]2 ion is formed quantitatively since it is more stable than the [Ag(CN)2] ion, the excess of cyanide may be determined by the Liebig-Deniges method. The metal ion determinations are, however, more conveniently made by titration with EDTA see the following sections. 

Situation and Criteria A method was to be developed to determine trace amounts of cyanide (CN ) in waste water. The nature of the task means precision is not so much of an issue as are the limits of detection and quantitation (LOD, LOQ), and flexibility and ease of use. The responsible chemist expected cyanide levels below 2 ppm. 

Acute-Duration Exposure. Information is available regarding the effects of acute-duration inhalation exposure of humans to acrylonitrile and the effects are characteristic of cyanide-type toxicity. Quantitative data are limited but are sufficient to derive an acute inhalation MRL. Further studies of humans exposed to low levels of acrylonitrile in the workplace would increase the confidence of the acute MRL. Studies in animals support and confirm these findings. No studies are available on the effects of acute-duration oral exposure in humans however, exposure to acrylonitrile reveals neurological disturbances characteristic of cyanide-type toxicity and lethal effects in rats and mice. Rats also develop birth defects. Animal data are sufficient to derive an acute oral MRL. Additional studies employing other species and various dose levels would be useful in confirming target tissues and determining thresholds for these effects. In humans, acrylonitrile causes irritation of the skin and eyes. No data are available on acute dermal exposures in animals. 

The sample is extracted with a mixture of hexane, acetone and water. After separation, the hexane phase is reduced in volume and divided into two aliquots, one of which is first shaken with 7% fuming sulphuric acid to remove lipids, and then with cyanide to eliminate interference by elemental sulphur. The other aliquot is evaporated to dryness and heated with ethanolic potassium hydroxide. The two aliquots are injected into a gas chromatograph fitted with a glass capillary column and an electron capture detector. Hexabromobenzene is used as an internal standard. Polychlorinated biphenyls are determined quantitatively by comparing the peaks of the sample with those of Clophen A... 

Zinc is determined quantitatively by titration of the acid solubilized material with K ferro-cyanide, the endpoint being indicated when a drop of uranyl nitrate produces on a porcelain plate a brown tinge with a drop of titrated mixt. Metallic Zn is determined by the hydrogen evolution method using a gas burette (Ref 8)... 

Before we obtained the X-ray structure determinations of both the knotted and unknotted dicopper(I) complexes, we could identify them after careful comparative H NMR and mass spectroscopy studies performed not only on the dinuclear complexes but also on their respective free ligands afforded by demetalation. Treatment of Cii2(m-43) + by a large excess of potassium cyanide led indeed quantitatively to a plain 43-membered macrocycle whereas an analogous treatment of Cii2(K-86r+ led to the free knot K-86 whose topological chirality could be demonstrated by NMR and mass spectroscopy (Figure 20). 

The tests conducted by the institute were qualitative, not quantitative, analyses. In other words, they could only determine whether or not cyanide was present, not how much of it was there. As to whether or not homicidal gassing with hydrogen cyanide took place in Auschwitz, these analyses are worthless, for three reasons ... 

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