Cyanide instrumental methods

Elemental composition Cu 70.95%, C 13.41%, N 15.64%. Copper(I) cyanide is decomposed in nitric acid and the acid extract diluted appropriately and analyzed for copper hy various instrumental methods (see Copper). 

One of the reviews cited earlier enumerates spectrophotometric methods for the determination of cyanide up to 1962 [8]. Also, instrumental methods such as colorimetric and spectrophotometric methods, electroanalytical methods, catalytic methods, gas chromatography methods, radiochemical methods, and miscellaneous methods for determination of cyanide up to 1977 have been summarized by Williams [7]. The instrumental methods developed since 1977 are considered here. 

Among the instrumental methods, electrogravimetry (Sec.2.3.2) can be used but the best results are obtained from the silver cyano-complex. But because of the high toxicity of cyanides, the method cannot be recommended. 

Elemental composition Ba 72.52%, C 12.68%, N 14.79%. Barium metal can be analyzed by various instrumental and wet methods (see Barium). Cyanide ion in the aqueous solution of the compound may be determined by using a cyanide ion-specific electrode or by colorimetry using pyridine-barbituric acid reagent (APHA, AWWA, and WEF. 1999. Standard Methods for the Examination of Water and Wastewater, 20th ed., Washington, DC American Public Health Association). 

The cyanide method is presently the only method for the determination of ketone groups in the polymers and was highly instrumental in the chemical characterization of degraded and oxidized celluloses. The use of this method enabled the development of the first two systems for the preparation of keto-cellulose, namely by mild oxidation with aqueous bromine at low pH values at room temperature [441,442] and by mild oxidation with hydrogen peroxide at pH 10 and 80°C [420,443]. 

The automated method differs from the ICSH method chiefly in that oxidation and ligation of heme iron occur after the hemes have been released from globin. Therefore, ferricyanide and cyanide need not diffuse into the hemoglobin and methemoglobin, respectively. Because diffusion is rate-limiting in this reaction sequence, the overall reaction time is reduced from approximately three minutes for the manual method to 3 —15 seconds for the automated method. Reaction sequences in the Coulter S + II and the Technicon H 1 and H 2 are similar. Moreover, similar reactions are used in the other Coulter systems and in the TOA and Unipath instruments. 

Spectrophotometric procedures, including absorptimetric and fluo-rimetric, will continue to be popular and important because they can be sensitive and accurate, and because the necessary instruments are now famihar laboratory tools. Intrinsically, fluorimetric methods can be several orders of magnitude more sensitive than absorptimetric. To date, most direct fluorimetric methods are for the determination of metals, while anions are determined by their quenching action on fluorescent compounds. Hopefully, other new direct fluorimetric reagents for anions similar to the one described above for cyanide ion using quinone monoxime benzene sulfonate ester will be developed either as the result of chance observations or the application of increased fundamental knowledge of the fluorescence process. There probably will be few if any major advances in the quality of the instruments used in these methods improved methods mainly will be the result of more sensitive and more selective analytical reagents. 

It is common to use both types of procedures to investigate exposures in the workplace. Direct-reading methods are ideal for quick checks especially when the contaminants are known or suspected. However, they are limited in accuracy. No instrument can read every contaminant. Two common instruments, organic vapor analyzer (OVA) and the photoionizer (HNU), can detect hundreds of compounds but cannot detect important toxic chemicals such as phosgene, cyanides, arsenic, or chlorine. 

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