Development of a sulfate microelectrode for profiling environmental biofilms

Abstract

Microelectrodes can be used for profiling environmental biofilms. Currently there is no sulfate microelectrode available for studying sulfate reduction in biofilms. In this study, a sulfate microelectrode was fabricated and tested in measurement of environmental biofilms for the first time. The composition of the sulfate-sensing membrane in the microelectrode was optimized. The sulfate microelectrode, with a tip diameter of 20 micrometres, displayed satisfying selectivity to SO42-. It exhibited log-linear response to sulfate concentration change with a Nernstian slope of -25.8 mV per concentration decade. The linear detection range was 10-5 M to 10-2 M SO42- with a detection limit of 10-5 M SO42- in water. The response time was 90 seconds. The sulfate microelectrode was applied on environmental biofilm samples. The sulfate profile obtained indicated the sulfate concentration change inside the biofilm. In conclusion, a sulfate microelectrode with satisfying characteristics was fabricated successfully and was useful for characterizing environmental biofilms.