The design and construction of an oxygen micro-electrode for monitoring 20-100 microliter volumes

Full instructions are given for the construction of a micro-respirometer. It is based on a membrane-covered platinum electrode of 10 micron diameter that consumes little oxygen. The reaction chamber, made entirely of glass, can be varied in volume between 20 and 100 microliter by adjusting the sealer assembly. Although specifically designed to study the properties of small samples of mitochondria from tiny organisms, it can be used equally well either for oxygen dissolved in aqueous solutions or dry gas mixtures containing oxygen. Measurements can be made with about one-hundredth the amount of material required for commercially available macro-respirometers, and when connected via an impedance-matching device to a pen recorder it gives a stable output of 100-200 mV in air.