O2k-Standard Operating Procedures
An 'Oxygraph' gives a graphical record of oxygen concentration over time. The 'linear slope' is related to respiratory activity. Evaluation of linearity, of small changes, and of oxygen-dependent corrections of flux is difficult.
The Oxygraph-2k shows not only oxygen concentration, but in addition yields a plot of respiratory rate in various selected units: oxygen flux per volume or per unit biological sample.
A polarographic oxygen sensor (OroboPOS) is placed in each Oxygraph-2k chamber. The POS yields a signal which is calibrated in terms of concentration of dissolved oxygen [µmol O2 per litre]. The signal may also be displayed in terms of partial pressure of oxygen [kPa or mmHg]. Barometric pressure is recorded continuously for calibration, and accurate calculation of oxygen solubility is integrated into the DatLab software.
When the Oxygraph-2k chamber is filled with an aqueous solution containing the sample or substances that utilize dissolved oxygen, and the chamber is closed, then the decline of oxygen concentration over time is proportional to the respiratory activity or oxygen flux.