Electrochemical sensors based on electrodes modified with synthetic hydrotalcites

The behaviour of electrodes modified with conductive hydrotalcites is reported as far as their electrochemical and electrocatalytic properties in basic solutions are concerned. In particular, cobalt and nickel based materials are compared. Pt electrodes, modified with a film of Ni/Al-NO3 or Co/Al-NO3 hydrotalcite, obtained by direct electrosynthesis, have been evaluated as amperometric sensors for oxidizable substrates in flow systems. Mono and polyhydric compounds have been analysed to compare the performances of the two sensors. The experimental conditions to obtain the best current signal in terms of reproducibility and sensitivity have been established as to the working and activation potential of the electrode, concentration and flow rate of the carrier solution, volume of the solution to be injected. The Co based HT is not responsive to monohydric compounds, and shows a sensitivity worse than the Ni based HT. The modified electrodes are simple and rapid to prepare, and can operate continuously in flowing solutions for 1–2 days at least.