Oxygen

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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O₂                32.00

Oxygen CAS RN®: 7782-44-7; UNII: S88TT14065.

1 DEFINITION

Oxygen contains NLT 99.0% of oxygen (O₂) by volume.

2 IDENTIFICATION

A. The paramagnetic signal exhibited by the Sample gas in the Assay confirms the presence of oxygen.

B. The Sample gas in the Assay meets the Acceptance criteria.

3 ASSAY

Procedure

The certified standards called for in the following test are listed in Reagents, Indicators, and Solutions.

Zero gas: Nitrogen certified standard

Span gas: Oxygen certified standard

Sample gas: Oxygen under test

Mode: Paramagnetic oxygen measurement (see Medical Gases Assay 〈415〉)

Analysis: Determine the concentration of oxygen in percentage by volume in Oxygen using a suitable paramagnetic analyzer. Acceptance criteria: NLT 99.0% by volume

4 IMPURITIES

Change to read:

See Impurities Testing in Medical Gases (ERR 1-Nov-2020) 〈413〉. The detector tubes called for in the following tests are listed in Reagents, Indicators, and Solutions. If the label indicates that Oxygen is produced by the air-liquefaction process, then the Impurities tests are not required.

4.1 Limit of Carbon Dioxide

Sample: Detector tube manufacturer's recommended volume, ±5% of Oxygen

Analysis: Pass the Sample through a carbon dioxide detector tube at the rate specified for the tube by the detector tube manufacturer. Acceptance criteria: NMT 300 ppm

4.2 Limit of Carbon Monoxide

Sample: Detector tube manufacturer's recommended volume, ±5% of Oxygen

Analysis: Pass the Sample through a carbon monoxide detector tube at the rate specified for the tube by the detector tube manufacturer. Acceptance criteria: NMT 10 ppm

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in pressurized containers. Container connections shall be appropriate for Oxygen. Adaptors shall not be used to connect containers to patient-use supply system piping or equipment.

Labeling: Label states if Oxygen was produced by the air-liquefaction process. Where it is piped directly from the cylinder or storage tank to the patient point of use, label each outlet “Oxygen”.