Fabrication of Redox Potential Microelectrodes for Studies in Vegetated Soils or Biofilm Systems

A new method for construction of redox potential microelectrodes has been successfully developed in this study. The new construction method consists of four major steps: (a) pulling a glass pipet; (b) trimming the micropipet tip to obtain a suitable size; (c) filling the micropipet with a low-melting point alloy; and (d) plating platinum onto the alloy surface. This method can be used to make redox potential microelectrodes with tip sizes as small as 1−3 μm for biofilm research and with tip sizes between 20 and 40 μm for in-situ measurements in plant-grown soil systems. The microelectrodes retain their characteristics for a few weeks. The high Nernst slope (57−61 mV/pH unit using pH buffer solutions saturated with quinhydrone to calibrate the electrodes), the short response time (ca. 0 s to 3 min), the high tolerance capacity for the potential interference ions, and the increased rigidity are features of this new method which make the redox potential microelectrodes suitable for studies in both biofilm and soil systems.