Cyanide potentiometric detection

Many IC techniques are now available using single column or dual-column systems with various detection modes. Detection methods in IC are subdivided as follows [838] (i) electrochemical (conductometry, amper-ometry or potentiometry) (ii) spectroscopic (tJV/VIS, RI, AAS, AES, ICP) (iii) mass spectrometric and (iv) postcolumn reaction detection (AFS, CL). The mainstay of routine IC is still the nonspecific conductometric detector. A significant disadvantage of suppressed conductivity detection is the fact that weak to very weak acid anions (e.g. silicate, cyanide) yield poor sensitivity. IC combined with potentiometric detection techniques using ISEs allows quantification of selected analytes even in complex matrices. The main drawback... 

The potentiometric detection of the endpoint of precipitation titrations is very often used because not many visual indicators are available, in particular when mixtures of analytes are titrated. Halides, cyanide, sulfide, chromate, mercaptans, and thiols can be titrated with silver nitrate, using the silver sulfide-based ISE. Also complex mixtures, such as sulfide, thiocyanide, and chloride ions, or chloride, bromide, and iodide ions, can be titrated potentio-metrically with silver(I) ions. When the solubility of a compound formed during titration is too high, nonaqueous or mixed solvents are used, for example,... 

Flow setup used for the potentiometric detection of cyanides. EC electrochemical cell containing two similar silver amalgam electrodes HC holding coil SV selection valve. 

B. Vallejo-Pecharroman, M.D. Luque de Castro, Determination of cyanide by a pervaporation-UV photo-dissociation-potentiometric detection approach. Analyst 127 (2002) 267-270. 

The potentiometric determination of cyanide using ion selective electrodes has become yet another very popular technique, because it is convenient, rapid, and sensitive method of analysis (Frant et al, 1972). Microdiffusion of biological samples containing cyanide is recommended prior to potentiometric determination. The use of a cyanide ion-selective electrode in combination with the Conway microdiffusion method for the measurement of cyanide concentrations in human red blood cells and plasma was reported with remarkable recovery of cyanide (Yagi et al, 1990). Ion chromatographic determination of sulfide and cyanide in real matrices by using pulsed amperometric detection on a silver electrode was reported by Giuriati et al. (2004). 

The accepted by EPA potentiometric methods involve selective electrodes for fluorides, cyanides, nitrates, ammonia, and sulfides detection [20]. The potentiometric characteristics of the anion-selective sensors are strongly dependent on the anion receptor design and properties [25]. At this time, molecular recognition of anions by synthetic receptors is an expanding research area. 

An automated system for potentiometric determination of free and total cyanide in wastewaters is by employing a homogeneous membrane tubular ion-selective electrode [38]. After the electrode is assembled, it is connected to a system composed of 3 three-way solenoid valves, sample line, carrier line, acid stream, and gas diffusion chamber. A turbo pascal computer program performs all the steps involved in data acquisition and processing. The proposed analytical procedure offers operational simplicity, since detection is performed by a cyanide ion-selective tubular electrode, and is fast and easy to assemble. 

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