Packaging and storage
Preserve in cylinders.
Change to read:
Prepare a gas chromatograph as directed in the Assay,
and inject USP Nitrogen RS
and the nitrogen sample into the gas chromatograph. The retention time of the major peak in the chromatogram of the nitrogen sample corresponds to that in the chromatogram of the USP Nitrogen RS
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: no appreciable odor is discernible.
NOTEReduce the container pressure by means of a regulator. Measure the gases with a gas volume meter downstream from the detector tube in order to minimize contamination or change of the specimens.
Pass 1000 ± 50 mL through a carbon monoxide detector tube (see under Reagents
in the section Reagents, Indicators, and Solutions
) at the rate specified for the tube: the indicator change corresponds to not more than 0.001%.
Limit of oxygen
Not more than 1.0% of oxygen is present, determined as directed in the Assay.
Change to read:
Introduce a specimen of Nitrogen into a gas chromatograph by means of a gas sampling valve. Select the operating conditions of the gas chromatograph such that the standard peak signal resulting from the following procedure corresponds to not less than 70% of the full-scale reading. Preferably, use an apparatus corresponding to the general type in which the column is 3 m in length and 4 mm in inside diameter and is packed with a molecular sieve prepared from a synthetic alkali-metal aluminosilicate capable of absorbing molecules having diameters of up to 0.5 nm, which permit complete separation of oxygen from nitrogen. Use industrial grade helium (99.99%) as the carrier gas, with a thermal-conductivity detector, and control the column temperature: the peak response produced by the assay specimen exhibits a retention time corresponding to that produced by
the USP OxygenHelium RS
and is equivalent to not more than 1.0% of oxygen when compared to the peak response of the USP OxygenHelium RS
indicating not less than 99.0%, by volume, of N2