Improved fabrication of double-barreled recessed cathode O2 microelectrodes

Polarographic recessed cathode gold microelectrodes are the preferred type of O2 microelectrode for tissue measurements, but the method originally described for their construction is difficult. An improved method of constructing such electrodes consists of several steps: 1) insertion of a rod made of a special low-melting point alloy into a pulled glass micropipette, 2) heating of the electrode tip as the alloy is pushed toward the tip, 3) beveling, and 4) gold plating the alloy, leaving a recess of the desired length. This method can be used to make single- or double-barreled electrodes in which the O2 barrel is as small as 2-3 micron. The electrodes retain their characteristics for several weeks.