Cyanide determinations

Environmental. The toxicity of cyanide in the aquatic environment or natural waters is a result of free cyanide, ie, as HCN and CN . These forms, rather than complexed forms such as iron cyanides, determine the lethal toxicity to fish. Complexed cyanides may revert to free cyanide under uv radiation, but the rate is too slow to be a significant toxicity factor. Much work has been done to estabhsh stream and effluent limits for cyanide to avoid harmful effects on aquatic life. Fish are extremely sensitive to cyanide, and the many tests indicate that a free cyanide stream concentration of 0.05 mg/L is acceptable (46), but some species are sensitive to even lower concentrations. 

Plasma Deproteinization with trichloroacetic acid bromination of supernatant and treatment with pyridine-p-phenylene diamine Spectrophotometry (thiocyanate- cyanide determination) 0.07 ppm 96 (thiocyanate) Pettigrew and Fell 1972... 

Erythrocyte suspension Sample purged absorption of hydrogen cyanide in sodium hydroxide conversion of thiocyanate to cyanide by potassium permanganate oxidation Spectrophotometry (thiocyanate- cyanide determination) No data 93-97 McMillan and Svoboda 1982... 

Blood Separation in a microdiffusion cell absorption in methemoglobin solution Spectrophotometric (free cyanide determination) 0.4 pg/mL 80 Tomoda and Hashimoto 1991... 

Laforge M, Buneaux F, Houeto P, et al. 1994. A rapid spectrophotometric blood cyanide determination applicable to emergency toxicology. J Anal Toxicol 18 173-175. 

Lui et al. [109] have described an automated system for determination of total and labile cyanide in water samples. The stable metal-cyanide complexes such as Fe(CN)63 are photo-dissociated in an acidic medium with an on-line Pyrex glass reaction coil irradiated by an intense mercury lamp. The released cyanide is separated from most interferences in the sample matrix and is collected in a dilute sodium hydroxide solution by gas diffusion using a hydrophobic porous membrane separator. The cyanide ion is then separated from remaining interferences such as sulphide by ion exchange chromatography and is detected by an amperometric detector. The characteristics of the automated system were studied with solutions of free cyanide and metal-cyanide complexes. The results of cyanide determination for a number of wastewater samples obtained with this method were compared with those obtained with the standard method. The sample throughput of the system is eight samples per hour and the detection limit for total cyanide is 0.1 pg L 1. 

Conversely, the calibration for the cyanide determination poses no problem. Free cyanide is found, for example, in untreated liquors from electroplating processes. Since these samples also contain transition metal ions, part of the cyanide exists in complexed form, whereby the various metal cyano complexes differ significantly in their stability. 

L. Solujic, E.B. Milosavljevic, M.R. Straka, Total cyanide determination by a segmented flow injection-on-line UV digestion-amperometric method, Analyst 124 (1999) 1255. 

Abstract. Cyanides and hydrocyanic acid are one of the priority pollutants being most toxic. Therefore, it is very important to monitor cyanide concentration with specific and sensitive analytical methods. Some analytical methods for cyanide determination were presented in the last years spectrophotometer, potentiometer with silver cyanide electrode and titrimetric method. The paper presents original results concerning the spectrometric method and argentometric titration utilization for the measurement of cyanide concentration in some distilled alcoholic drinks from plums, grapes and apricots. The obtained cyanide concentrations vary between 0.0162 and 0.0970 mg/lOOmL, being under the imposed limits. 

H. Muller, Chloride and cyanide determination by use of the flow injection method using ion-selective flow-type electrodes, 3rd Symposium on ion-selective electrodes, Matrafiired, 279 (1980). 

Reif, H. The use of the ion-selective electrode for cyanide determination in cigarette smoke Fachliche Mitt. 

H. Muller, Chloride and Cyanide Determination by Use of the Flow Injection Method Using Ion-Selective Flow-Type Electrodes. Anal. Chem. Symp. Ser., 8 (1981) 279. 

A. Specific levels. Cyanide determinations are rarely of use in emergency management because they cannot be performed rapidly enough to influence initial treatment. In addition, they must be interpreted with caution because of a variety of complicating technical factors. 

Jin, W. J., Costa-Fernandez, J. M., Pereiro, R. and Sanz-Medel, A. (2004) Surface-modihed CdSe Quantum Dots as Luminescent Probes for Cyanide Determination. Anal. Chim. Acta, 522,1-8. 

Table 10. Headspace gas chromatography procedures for cyanide determination.

Cyanide Chloramine-T/pyridine-barbituric acid Spectrophotometry/ Amperometry 0.002-2.0 mg CN Gas-diffusion preconcentration/UV-photolysis for total cyanide determination/ standard method ISO 14403... 

Figure 4 Simplified flow diagram for total cyanide determination with UV digestion and distillation.

Copper cyanide Determination of Cu " after preparation with strong acids, hexacyano... 

Total cyanide determination requires appropriate destructive procedures to be implemented in order to decompose the sample matrix and liberate hydrogen cyanide. To this end, alternative approaches have been applied, e.g. microwave-assisted digestion [34] and photodissociation [35-37]. 

A.S. Tauliq, AM.S. Abulkibash, Differential electrolytic potentiometric detector in flow injection analysis for cyanide determination, J. Flow Injection Anal. 24 (2007) 9 12. 

M.C. Quaresma, M.F. de Carvalho, F.A. Meirelles, V.M. Santiago, R.E. SanteUi, AppUcation of hydrocyanic acid vapor generation via focused microwave radiation to the preparation of industrial effluent samples prior to free and total cyanide determinations by spectrophotometric flow injection analysis. Anal. Bioanal. Chem. 387 (2007) 1017-1025. 

These methods are highly sensitive and specific for cyanide determination. These methods are based on the formation of polymethine dyes, for the example benzidine-pyridine method is used. Also, the barbituric acid method can be recommended. One general procedure of determining CN with bromine-pyridine-aromatic amine is described below. 

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