# Difference between revisions of "Oxygen flux"

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Oxygen flux

## Description

Oxygen flux, JO2, is a specific quantity. Oxygen flux is oxygen flow, IO2 [mol·s-1 per system] (an extensive quantity), divided by system size. Flux may be volume-specific (flow per volume [pmol·s-1·mL-1]), mass-specific (flow per mass [pmol·s-1·mg-1]), or marker-specific (flow per mtEU). Oxygen flux (e.g., per body mass, or per cell volume) is distinguished from oxygen flow (per number of objects, such as cells), IO2 [mol·s-1·x-1]. These are different forms of normalization of rate.

Abbreviation: JO2

```Contributed by Gnaiger E (2020-01-15)
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## Which SI units should be used?

• The SI unit for volume
1000 L = 1 m3
1 L = 1 dm3
1 mL = 1 cm3
1 µL = 1 mm3
• Convert various units of volume-specific oxygen flux, JO2, to SI units [nmol·s-1·L-1] = [pmol·s-1·mL-1]
1 µmol O2∙min-1∙L-1 ∙ [1000 nmol∙(1 µmol)-1] ∙ [1 min∙(60 s)-1] = 16.67 nmol O2∙s-1∙L-1
1 nmol O2∙min-1∙mL-1 ∙ [1000 pmol∙(1 nmol)-1] ∙ [1 min∙(60 s)-1] = 16.67 pmol O2∙s-1∙mL-1
1 nmol O2∙h-1∙mL-1 ∙ [1000 pmol∙(1 nmol)-1] ∙ [1 min∙(60 s)-1] ∙ [1 h∙(60 min)-1] = 0.2778 pmol O2∙s-1∙mL-1
1 natom O∙s-1∙L-1 ∙ [1 nmol O2∙(2 natm O)-1] = 0.5 nmol O2∙s-1∙L-1
1 natom O∙min-1∙L-1 ∙ [1000 pmol O2∙(2 natom O)-1] ∙ [1 min∙(60 s)-1] = 8.33 pmol O2∙s-1∙L-1
• Convert VO2max/M from ergometric to SI units
1 mL O2∙min-1∙kg-1 (at STPD) ∙ [1000 µmol∙(22.392 mL)-1] ∙ [1 min∙(60 s)-1] = 0.744 µmol O2∙s-1∙kg-1
• There is a difference between oxygen flux per volume and oxygen concentration change per time
The oxygen concentration change per time (= rate of concentration change) is expressed in units [µmol O2∙L-1∙s-1].
By definition the rate of concentration change is zero in an open system at steady-state, when the concentration in the system does not change at any respiratory flux by the sample enclosed in the open system.
Oxygen flux per volume (= volume-specific oxygen flux) is expressed in units [µmol O2∙s-1∙L-1] or [nmol O2∙s-1∙L-1]
By definition the volume-specific oxygen flux is the advancement of reaction per volume of the reaction chamber.
Oxygen flux per mass (= mass-specific oxygen flux) is expressed in units [µmol O2∙s-1∙kg-1] = [pmol O2∙s-1∙mg-1]
By definition the mass-specific oxygen flux is the advancement of reaction per mass of the sample enclosed in the reaction chamber.

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