Nitrogen 97 Percent
If you find any inaccurate information, please let us know by providing your feedback here
This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
1 DEFINITION
Nitrogen 97 Percent is Nitrogen produced from air by physical separation methods. It contains NLT 97.0%, by volume, of nitrogen (N₂).
2 IDENTIFICATION
A. The flame of a burning wood splinter is extinguished when inserted into a test tube filled with Nitrogen 97 Percent. [Note—Exercise caution.]
3 ASSAY
Procedure
Standard: Oxygen–helium certified standard (see Reagents, Indicators, and Solutions)
Sample: Nitrogen 97 Percent
Chromatographic system
(See Chromatography 〈621〉, System Suitability.)
Mode: GC
Detector: Thermal conductivity
Column: 3-m length × 4-mm inside diameter: molecular sieve prepared from a synthetic alkali-metal aluminosilicate capable of absorbing molecules having diameters of up to 0.5 nm and completely separating oxygen from nitrogen
Carrier gas: Helium (99.99%)
Temperature: Thermostatically controlled
Analysis
Samples: Standard and Sample
Introduce the Samples separately into the gas chromatograph by means of a gas sampling valve.
Acceptance criteria: The peak response produced by the Sample exhibits a retention time corresponding to that produced by the Standard and is equivalent to NMT 3.0% of oxygen when compared to the peak response of the Standard, indicating NLT 97.0%, by volume, of nitrogen (N₂).
4 IMPURITIES
[Note—Reduce the container pressure by means of a regulator. Measure the gases with a gas volume meter downstream from the detector tube to minimize contamination or change of the specimens.]
Carbon Dioxide
Sample: 1000 ± 50 mL
Analysis: Pass the Sample through a carbon dioxide detector tube (see Reagents, Indicators, and Solutions) at the rate specified for the tube.
Acceptance criteria: The indicator change corresponds to NMT 300 ppm
Carbon Monoxide
Sample: 1000 ± 50 mL
Analysis: Pass the Sample through a carbon monoxide detector tube (see Reagents, Indicators, and Solutions) at the rate specified for the tube.
Acceptance criteria: NMT 10 ppm
Sulfur Dioxide
Sample: 1000 ± 50 mL
Analysis: Pass the Sample through a sulfur dioxide detector tube (see Reagents, Indicators, and Solutions) at the rate specified for the tube.
Acceptance criteria: NMT 5 ppm
Limit of Nitric Oxide and Nitrogen Dioxide
Sample: 500 ± 50 mL
Analysis: Pass the Sample through a nitric oxide–nitrogen dioxide detector tube (see Reagents, Indicators, and Solutions) at the rate specified for the tube.
Acceptance criteria: NMT 2.5 ppm
Limit of Oxygen
Analysis: Determined as directed in the Assay
Acceptance criteria: NMT 3.0%
5 SPECIFIC TESTS
Odor
Analysis: Carefully open the container valve to produce a moderate flow of gas. Do not direct the gas stream toward the face, but deflect a portion of the stream toward the nose.
Acceptance criteria: No appreciable odor is discernible.
6 ADDITIONAL REQUIREMENTS
Packaging and Storage: Preserve in cylinders or in a low-pressure collecting tank.
Labeling: Where it is piped directly from the collecting tank to the point of use, label each outlet “Nitrogen 97 Percent”.
