(Ph. Eur. monograph 0417)
Oxygen should be kept in approved metal cylinders, the shoulders of which are painted white and the remainder black. The cylinder should carry a label stating ‘Oxygen’. In addition, ‘Oxygen’ or the symbol ‘O2’ should be stencilled in paint on the shoulder of the cylinder.
When Oxygen is intended for use in a room in which magnetic resonance imaging (MRI) is being performed, the cylinder and fittings should be made from suitable non-ferromagnetic materials and labelled accordingly.
O2 32.00 7782-44-7
DEFINITION
Content
Minimum 99.5 per cent V/V of O2.
This monograph applies to oxygen for medicinal use.
CHARACTERS
Appearance
Colourless gas.
Solubility
At 20 °C and at a pressure of 101 kPa, 1 volume dissolves in about 32 volumes of water.
PRODUCTION
Oxygen is produced by a purification process followed by cryodistillation of the ambient air.
Carbon dioxide
Maximum 300 ppm V/V, determined using an infrared analyser (2.5.24).
Gas to be examined: Filter the substance to be examined to avoid stray light phenomena.
Reference gas (a): Oxygen R.
Reference gas (b): Mixture containing 300 ppm V/V of carbon dioxide R1 in nitrogen R1.
Calibrate the apparatus and set the sensitivity using reference gases (a) and (b). Measure the content of carbon dioxide in the gas to be examined.
Carbon monoxide
Maximum 5 ppm V/V, determined using an infrared analyser (2.5.25).
Gas to be examined: Filter the substance to be examined to avoid stray light phenomena.
Reference gas (a): Oxygen R.
Reference gas (b): Mixture containing 5 ppm V/V of carbon monoxide R in nitrogen R1.
Calibrate the apparatus and set the sensitivity using reference gases (a) and (b). Measure the content of carbon monoxide in the gas to be examined.
Water
Maximum 67 ppm V/V, determined using an electrolytic hygrometer (2.5.28).
Assay
Determine the concentration of oxygen using a paramagnetic analyser (2.5.27).
IDENTIFICATION
It complies with the limits of the assay.
TESTS
Carbon dioxide
Maximum 300 ppm V/V, determined using a carbon dioxide detector tube (2.1.6).
Carbon monoxide
Maximum 5 ppm V/V, determined using a carbon monoxide detector tube (2.1.6).
Water vapour
Maximum 67 ppm V/V, determined using a water vapour detector tube (2.1.6).
STORAGE
As a compressed gas or liquid in appropriate containers, complying with the legal regulations. Oils and grease are not to be used unless they are oxygen-compatible.
IMPURITIES
Specified impurities A, B, C.
A. CO2: carbon dioxide,
B. CO: carbon monoxide,
C. H2O: water.
