Hydrogen cyanide detectors

HCN = hydrogen cyanide HPLC = high performance liquid chromatography NaOH = sodium hydroxide GC = gas chromatography ECD = electron capture detector NPD = nitrogen-phosphorus detector UV = ultraviolet detector. 

AgN03 = silver nitrate CICN = cyanogen chloride CN" = cyanide ion CNATC = cyanides not amenable to chlorination (Rosentreter and Skogerboe 1992) AAS = atomic absorption spectroscopy EPA = Environmental Protection Agency FIA = flow injection analysis GC/ECD = gas chromatograph/electron capture detector HCN = hydrogen cyanide NaOH = sodium hydroxide NIOSH = National Institute for Occupational Safety and Health... 

Bond et al. [68] have described a method for the simultaneous determination of down to lmg L 1 free sulphide and cyanide by ion chromatography, with electrochemical detection. These workers carried out considerable exploratory work on the development of ion chromatographic conditions for separating sulphide and cyanide in a basic medium (to avoid losses of toxic hydrogen cyanide and hydrogen sulphide) and on the development of a suitable amperometric detector. 

Fig. 2.23 shows the separation achieved on a 12 anion standard by this procedure. Sulphide, cyanide, bromide, and sulphite are detected at the silver electrode while nitrite, nitrate, phosphate and sulphate produce no response. Due to the low dissociation of hydrogen sulphide and hydrogen cyanide following protonation by the suppressor column, they are not detected by the conductivity detector. 

Hydrogen cyanide 20.0 mg m-3 6 min tubes, eel enzyme detector ticket Kit conducts 25 tests for each agent... 

FIGURE 2-24. Separation of b-, e-, and f-amides. Column Corasil II (silica, 37-50 Atm), 2 mm ID x 180 cm. Mobile phase methylene chloride, acetonitrile, methanol saturated with hydrogen cyanide (175/120/5). Flow rate 0.45 mL/min. Detector UV at 254 nm., L... 

In spring 1943, the Central Construction Management of Auschwitz ordered 10 gas detectors from the oven manufacturing firm of Topf and Sons.39 If these gas detectors had had anything to do with hydrogen cyanide they would have been ordered by the appropriate health authorities from the company DEGESCH, not by the Central Construction Management from the oven manufacturer Topf and Sons. 

This matter took a strange turn when Pressac recently found a document in the KGB archives in Moscow in which the company Topf and Sons confirms the aforementioned order of the gas detectors.41 This document makes reference to the telegram with the words Re.. Crematorium, gas detectors", but in the main text it is mentioned that it had not yet been possible to locate a supplier of indicators of hydrogen cyanide residue . So this document would have us believe that gas detectors were in fact devices for detecting hydrogen cyanide. But several factors ought to make an engineer suspicious ... 

The regulations of that time stipulated that after every delousing procedure utilizing hydrogen cyanide, a hydrogen cyanide residue detector had to be used to test the fumigated facilities to determine whether ventilation had been successful. Only then could the deloused rooms be entered without a protective gas mask. 

From the text of the order placed by the Central Construction Management ( Ship 10 gas detectors immediately, as discussed [...] quote price later ) it also becomes clear that after a discussion with the firm of Topf and Sons the Central Construction Management was in a position to expect that the devices would be shipped without delay and that the price would be up to Topf. Both, however, could only have been the case for products that were part of Topf s standard stock, and thus not possibly for hydrogen cyanide residue detectors. The latter is also clearly apparent from Topf s reply, which indicates the necessity for laborious research to locate the manufacturers of these detectors. 

Detection. Automatic detectors are available which detect attack concentrations of vapors of hydrogen cyanide, cyanogen chloride and cyanogen bromide. Draeger tubes are also available, as are water testing kits. 

Trace amounts of cyanide are usually determined by flow injection spectrophotometric procedures. The target species is first halogenated with chlora-mine-T, after which it reacts with a mixture of pyrazolone or barbituric acid and isonicotinic acid or pyridine to form a bluish-violet polymethine dye. The implementation of gas-diffusion modules in the flow setup for hydrogen cyanide separation avoids matrix interferences and enables the adaptation of inherently nonselective detectors, such as metallic silver-wire electrodes for potentiometric measurements. Total inorganic cyanide, including free and complexed species, such as iron-cyanide complexes, may be determined by sample decomposition with UV irradiation and further photometric or amperometric analysis. 

Detector tubes As with CO, hydrogen cyanide in air can be measured conveniently with reasonable accuracy by stain-length detector tubes. A typical reagent mixture is mercuric chloride and methyl red indicator. The hydrogen cyanide is converted to mercuric cyanide with the production of hydrogen chloride, which produces a pH change and as a result the indicator changes color to red ... 

Gas chromatography Gas chromatographic methods for cyanide usually involve using headspace techniques to detect hydrogen cyanide with the use of a nitrogen-phosphorus detector (NPD) or electron capture detector (BCD). Total cyanides can be analyzed in this way after conversion to hydrogen cyanide. 

Glass and metal containers are not recommended for collection of HCN samples this is due to adsorption of the compound onto the walls of such containers. Good results are achieved when HCN is adsorbed onto porous materials, from which it can be desorbed with a solvent or by using thermal methods. For HCN detection in biological samples (e.g., in blood), a HS analysis method may be applied. Hydrogen cyanide detectability with a thermionic nitrogen detector may reach 1 pg in a sample. 

This instrument is a handheld, portable CWA monitoring detector that uses IMS. The CAM-2 has the added detection algorithm for identifying hydrogen cyanide, phosgene, and chlorine, in addition to conventional CWAs. 

Portable gas detectors that clip on to a person s belt warn the wearer if he or she is being exposed to unacceptable levels of toxic gas. Probably the most common application in the process industries is for hydrogen sulfide (H2S), but they can be used for other chemicals, such as hydrogen cyanide (HCN). 

As part of the Megacity Initiative Local and Global Research Observations (MILAGRO) project, a comprehensive airborne study by Yokelson et al. reported the first detailed field measurements of biomass emissions in the Northern Hemisphere tropics [169]. Volatile emissions were measured from 20 deforestation and crop residue fires on the Yucatan peninsula. This included two trace gases which are often considered to be useful as indicators of biomass burning. One we have discussed before, namely acetonitrile, and the other is hydrogen cyanide. A variety of instrumentation was co-deployed for this investigation (FTIR spectroscopy, GD-FID, a GC-Trace Analytical Reduction Gas Detector, fluorescence and chemiluminescence instruments and various other spectrometers). PTR-MS was used to monitor methanol, acetonitrile, acetaldehyde, acetone, methyl ethyl ketone, methyl propanal, hydroxyacetone plus methyl acetate, benzene and 13 other volatile species. 

Cyanide in aqueous matrices is usually measured by colorimetric, titrimetric, electrochemical methods or by headspace gas chromatography with a nitrogen-specific detector, after pretreatment to produce hydrogen... 

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