ABSTRACT
Furthermore, microelectrodes for new measurable solutes were presented (Centonze et al., 1992; Cronenberg and van den Heuvel, 1991; Revsbech et al., 1988; Sweerts and de Beer, 1989).
Nitrate gradients could be measured in the littoral and profundal sediments of a mesoeutrophic lake with an ion-selective nitrate microelectrode (Sweerts and de Beer, 1989). The diffusion coefficient for glucose could be determined in a biocatalyst gel bead by measuring glucose profiles with a glucose enzyme microelectrode (Cronenberg and van den Heuvel, 1991). With a combined N20/oxygen-microelectrode, the conditions for denitrification in trickling fil ter biofilms could be formulated in detail (Dalsgaard and Revsbech, 1992). The microelectrode technique has become an important tool in biofilm re search. Because of its high sensitivity, the oxygen microelectrode is still the most used microelectrode in this research area. The purpose of this chapter is to show the fundamental properties o f oxygen microelectrodes. Furthermore, the biofilm tube reactor that was constructed especially for microelectrode
measurements under defined flow conditions is presented. Some results o f re cent studies are also presented to show the advantages o f the m icroelectrode.
