TWENTY YEARS OF RESPIROMETRY
Robert M. Arthur, President
Arthur Technology
Fond Du Lac, Wisconsin 54935
INTRODUCTION
In the early years of this century, biologists (including those working on wastewater treatment)
were very interested in developing a means of measuring the rate of metabolism of a living system.
Metabolism is the well-controlled cellular biochemical process in which food is utilized to create
energy and to synthesize new cells. In the process oxygen is utilized, and carbon dioxide is created
as shown in simple form in Figure 1. Biologists wanted to observe the changes that take place in this
system under various conditions and needed a means of continuously measuring a single well defined
parameter in this system. Certainly the easiest physical change to measure (given the analytical tools
available at that time) was the vacuum or pressure change caused by changes in gas volume. Since
two gases are involved in metabolism, it was necessary to remove one gas from the air space to observe
the change in volume of the other gas. Otto Warburg is generally given credit along with Sierp and
others for developing the first respirometer. An excellent book [1] on respirometric techniques describes in detail the use of this instrument. The Warburg respirometer shown in Figure 2 is still utilized
for the same purpose today but is used primarily in research.
LABORATORY RESPIROMETERS
To use the Warburg, a cellular suspension and food is placed in the small flask having a well
containing a caustic solution to absorb the carbon dioxide. The flask is connected to a fluid filled
manometer, and the entire setup is mechanically shaken to break up the water surface of the suspension and allow free transfer of oxygen and carbon dioxide between the dissolved and gaseous
state. As food is consumed by the cells, dissolved oxygen is utilized establishing a concentration
gradient and a transfer of oxygen from the gaseous state in the air space to the dissolved state. At
the same time the generated carbon dioxide is transferred from the dissolved state to the air space
where it is immediately absorbed by the caustic solution in the well. The net effect is a decrease in
gas volume in the air space which raises the level of fluid in the closed leg of the manometer and
FOOD
PRODUCTS
OF
METABOLISM
ENERGY
Figure 1. The Metabolic System.
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