Biomass-modified carbon paste electrodes for monitoring dissolved metal ions

Electrodes were prepared by incorporating dried, nonliving biomass of a common lichen, Ramalina stenospora, and Sphagnum (peat) moss in carbon paste. The electrodes were tested on solutions containing Pb(II) and Cu(II) ions by immersing the electrode in the solution for selected periods of time to accumulate ions. Following this the electrode was connected to a potentiostat and the applied voltage scanned from -1.0 to +0.5 V vs. SCE. Any adsorbed metal ions were stripped back into solution at the appropriate oxidizing voltage. The ratio of biomass to mineral oil to graphite has been found to be crucial to electrode performance. Different ratios of the three components using the lichen Ramalina stenospora were evaluated for maximum electrode performance. Only two electrode compositions gave a good electrode response for lead. Electrodes containing peat moss were superior in performance to lichen-containing electrodes for lead. Electrodes based on the lichens Cladina evansii and Letharia vulpina, the marine algae Ulva lactuca and Sargassum fluitans, the blue-green alga Spirulina platensis, and the aquatic plant Eichhornia crassipes did not respond to lead at all. All functioning electrodes studies showed a poor response toward copper(II) ions.