FABRICATION OF REDOX POTENTIAL MICROELECTRODES FOR STUDIES IN VEGETATED SOILS OR BIOFILM SYSTEMS

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