Long-lived sensors with replaceable surface for stripping voltammetric analysis: part II

The tape electrode, consisting of flexible polymer substrate, covered with carbon-containing paste and modified by calomel, has been developed as an alternative to the flexible voltammetric sensor with replaceable surface, which was made of a carbon-containing filament and modified beforehand by insoluble mercury diethyldithiocarbaminate. The tape electrode was fabricated using commercially available materials and the screen-printing technology. Optimal conditions have been chosen for the electrochemical 'activation' of the modifying layer of the calomel. These conditions provided a thin mercury layer comprising microscopic droplets 1-4 μm across on the electrode surface. Main experimental data obtained with the use of developed electrode followed the theoretical laws for the discharge-ionization of metals on the surface of solid and mercury thin-film electrodes. As compared to the carbon-containing filament, the tape electrode considerably extends the number of determinable amalgam-forming metals ions and allows decreasing their detection limits by more than one order of magnitude. The detection limit of 0.12 μg l-1 for copper, 0.02 μg l-1 for lead and cadmium and 0.05 μg l-1 for zinc was achieved after a 2 min accumulation. A high reproducibility of analytical response (0.6-2.3% R.S.D.) was achieved for nine repetitive measurements of 1 μg l-1 of these metals. The response values obtained with the tape sensor were directly proportional to the concentration of the metal ions over a broad concentration interval (0.1 μg l-1 to 0.5 mg l-1) at different accumulation times (120-10 s). Therefore, the newly developed low-toxic sensor can be used in automatic systems for environmental monitoring (at the trace level inclusive), processing solutions and waste waters