Electrolytic coatings (layers) deposited from palladium(II) salts

In contrast to a number of investigations concerning preparation of layers and coatings of palladium(II) oxides this communication describes a reproducible electrolytic preparation from activation baths containing Pd(II) ions of coatings with hydrated palladium oxides, in particular on platinum supports. The voltammetric curves of coatings formed in such a way are reproducible over the whole pH range and exhibit an irreversible cathodic-anodic couple of peaks. For the voltammetric curve on an active layer deposited on a platinum support from a solution of Pd(NO3)2 at pH 7.03 Ekp is + 0.02 V and Eap +0.33 V (vs SCE). The observed character of the pH dependences for the peak potentials and current densities with a similar, mostly linear, behaviour has been also observed with layers deposited on glassy carbon or nickel. The deposited layers containing hydrated palladium oxides exhibit oxidative activity as follows from voltammograms in slightly acidic to neutral and strongly alkaline region. These curves point to the ability to oxidize not only ethanol but also toluene used as a with difficulty oxidizable model substrate.

Some remarks concerning polarographic determination of sulphur-containing herbicides

The herbicide methomyl (2-methylthio-propionaldehyde-o-methylcarbamoyloxime) can be determined using fast scan differential pulse voltammetry with hanging mercury drop electrode by the measurement of the peak at -1.30 V (S.C.E.) which caused by the presence of methomyl in the ammoniacal buffer solution containing cobalt(II) salt. The peak current vs methomyl concentration dependence is linear over the concentration range 0.5 to 20.0 μg . l-1. The herbicide aldicarb (2-methyl-2(methylthio)propionaldehyde-o-methylcarbamoyloxime) is determined by its influence on the differential pulse voltammetric curve of copper(II) recorded in electrochemically enriched solution in acidic medium. The corresponding peak current at the potential + 0.08 V (S.C.E.) depends linearly on the aldicarb concentration in the range 0.07 to 5.00 μg ml-1.