A new type of microrespirometer

Abstract

Details of construction, operation and performance are given of a new microrespirometer, which makes use of the following principle. The respiration chamber (which has a volume of 70-150 [mu]ls) is closed by a thin mica membrane to which are attached two small mirrors. When the mica bulges (owing to evolution or absorption of gas in the chamber) the mirrors will tilt in opposite directions, and this is detected by a simple optical system. The mica membrane is restored to its original state by applying a suitable pressure to its outside surface. Then, knowing the volume of the chamber, the extent of the gas exchange in it can be calculated in terms of this pressure. The respiration chamber can be filled with any desired gas mixture, and two or more separate drops of fluid in it may be mixed at any time during the experiment. The apparatus can be set up at one temperature and used at a widely different one, and it can be sterilised. Comparative experiments show that for O2 uptakes of the order of 1 [mu]l per hr., the accuracy of this microrespirometer is not less than that of the ordinary Warburg manometer.