Electrochemical cyanide systems

An alternative approach, adopted by Albery et al. [59-61], is to determine the mechanism giving rise to the sensor response and to use this information together with the measured data at short times to calculate the final response. This was used for an electrochemical sensor system incorporating cytochrome oxidase where the steady-state responses of the measurement system were insufficiently fast for useful measurement of respiratory inhibitors such as cyanide, hydrogen sulphide, etc. By using mechanistic information, it was possible to successfully calculate the concentration in a test sample by real-time analysis of the sensor signals at short times after exposure to the test sample. The analysis could cope with the gradual loss of enzyme activity commonly found in these biosensor devices. 

On investigation of electrochemically deposited Ag coatings, it was established [23] that their open-circuit potentials (f g) possess all properties that are characteristic of equilibrium potentials. In contrast with Cu electrodes in cyanide system (see Section 2.4.1), no change in the Ag electrode mass was observed upon its daily exposure to the deaerated Ag(I)-cyanide solution. After the potential step perturbation, the equilibration proceeds rather rapidly and g acquires its initial... 

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... 

Except for the development of on-line systems for nutrients monitoring, the measurement of other inorganic non-metallic constituents is rather rare. Some commercial systems based on electrochemical sensing are proposed for the measurement of cyanide. A simple and rapid procedure for sulphide measurement in crude oil refinery wastewater has been developed [ 32 ]. Based on the de-convolution of the UV spectrum of a sample, this method has a detection limit of 0.5 mg L 1 and has been validated for crude oil refinery wastewater. 

In the case of the direct electrochemical approach, while the electrolysis conditions are less severe, the selection of the appropriate electrode material is still very important, and further reading on the use of stainless steel [93], platinum [94], graphite [95], doped Sn02 [92], doped Pb02 [86, 87, 96], and so on, is suggested. The economic viability of the electrochemical treatment approach is influenced in no small way by the cost and lifetime of the anode material this can easily make or break the field implementation of the process. Some authors have used high-surface area, porous anodes for cyanide treatment in order to combat the problems of mass-transport limitations so evident at cyanide concentrations below 100 ppm [88]. That system consists of a reticulated vitreous carbon porous anode that was activated for cyanide oxidation by the deposition of some copper oxide. The process looks very promising at the laboratory scale,... 

The surface scattering from a molecule may be affected by the presence of other chemical species in a much different way from that of the same molecule in solution— for instance, the observation of strong dependence of the scattering of pyridine from a silver electrode on the presence and concentration of chloride ions (see Section II.3.(i) or the interdependence of the pyridine signal on the presence of CO coadsorbed on a silver film in UHV conditions " or on the presence of cyanide anion in an electrochemical system to such a dependence one can add also the dependence on the pH. ... 

Nineteen AA were detected in beer samples derivatized with napthalene 23-dicarboxaldehyde (NDA) and cyanide (CN ) by capillary zone electrophoresis (CZE) with electrochemical detection Under the optimum conditions, the limits of detection (LODs) for individual AA were between 84 and 893 amol. An interesting method recently developed by Ruiz-Jimenez and Luque de Castro reported the determination of BA in nine solid food samples using a full-automated method based on pervaporation coupled online with CE and indirect UV detection. The pervaporator allowed leaching, formation of the volatile analytes, and their removal by evaporation and diffusion through a membrane. The isolated analytes were injected online into the CE system while the solid matrix remained in the pervaporator. With this approach, BA have been determined in fish, meat, and sausage, with LODs ranging between 0.2 and 0.6 fig/mL. 

Saji T, Yamada T, Aoyagui S (1975) Electron-transfer rate constants for redox systems of Fe(III)/Fe(II) complexes with 2,2 -bipyridine and/or cyanide ion as measured by the galvanostatic double pulse method. J Electroanal Chem Interfacial Electrochem 61 147-153... 

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