Electrochemical methods surfactant-selective electrodes

Electrochemical analytical techniques are a class of titration methods which in turn can be subdivided into potentiometric titrations using ion-selective electrodes and polarographic methods. Polarographic methods are based on the suppression of the overpotential associated with oxygen or other species in the polarographic cell caused by surfactants or on the effect of surfactants on the capacitance of the electrode. One example of this latter case is the method based on the interference of anionic surfactants with cationic surfactants, or vice versa, on the capacitance of a mercury drop electrode. This interference can be used in the one-phase titration of sulfates without indicator to determine the endpoint... 

Let us now discuss some applications of microemulsions in catalytic processes. It has been shown in [298] that the use of microemulsions instead of organic solvents for electrochemical reactions is advantageous from both economical and ecological reasons. The electrode/fluid interface in microemulsions probably consists of a dynamic layer of surfactant molecules packed more loosely on the electrode than in aqueous solutions. Microemulsions provide good yields of carbon-carbon addition products in reactions catalysed by cobalt complexes when preparing vitamin B 2. Excellent stereo-selective control in microemulsions made with the cationic surfactant cetyl trimethyl ammonium bromide was demonstrated for the catalytic cyclisation of 2-(4-bromobutyl)-2-cycIohexene-l-one to 1-decalone. Electrochemical synthesis may be a viable future approach to environmentally friendly chemical methods. 

Cathodic stripping voltammetry methods have been used in the determination of the OP insecticides Fenitrothion, Malathion " and Methyl Parathion. The influence of selected surfactants on the voltammetric determination of Fenitrothion and Malathion has been studied in detail, " and a new method described for the cathodic electrochemical determination of Methyl Parathion and other OPs using a bismuth film-modified glassy carbon electrode. The electrode behaviour was similar and favourable compared to that of mercury and a bare electrode, and its voltammetric response proportional to the concentration of Methyl Parathion in the 3.0 to lOOng/mL range with a detection limit of 1.2ng/mL. 

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