Prepared at the 53rd JECFA (1999) and published in FNP 52 Add 7 (1999), superseding specifications prepared at the 51st JECFA (1998), published in FNP 52 Add 6 (1998). ADI "No ADI necessary" established at the 24th JECFA in 1980. | |
SYNONYMS |
INS No. 941 |
DEFINITION |
This monograph defines nitrogen with a maximum oxygen content of 1%, which is suitable only for some food applications. There are food applications that require a higher purity (i.e., lower oxygen content). |
Chemical names |
Nitrogen |
C.A.S. number |
7727-37-9 |
Chemical formula |
N2 |
Formula weight |
28.0 |
Assay |
Not less than 99.0% v/v |
DESCRIPTION |
Colourless, odourless gas or liquid |
FUNCTIONAL USES |
Freezing agent, propellant, packaging gas |
CHARACTERISTICS |
|
IDENTIFICATION |
|
Flame test |
A flame is extinguished in an atmosphere of the sample |
PURITY |
|
Oxygen |
As declared by the vendor but not more than 1% v/v |
Carbon monoxide |
Not more than 10 �l/l |
TESTS |
|
PURITY TESTS |
|
Oxygen |
Use an oxygen analyser with a detector scale ranging from 0 �l/l to 100 �l/l and equipped with an electrochemical cell. The gas to be examined is passed through a detection cell containing an aqueous solution, generally potassium hydroxide. Oxygen in the sample gas produces variation in the electrical signal recorded at the outlet of the cell that is proportional to the oxygen content. Calibrate the analyzer according to the instructions of the manufacturer. Pass the gas through the analyser using a suitable pressure regulator and airtight metal tubes and operating at the prescribed flow-rates until constant readings are obtained. |
Carbon monoxide |
Pass 1050 � 50 ml of the gas sample through a carbon monoxide detector tube at the rate specified for the tube. The indicator change corresponds to not more than 10 �l/l. |
METHOD OF ASSAY |
Determine by Gas chromatography using the following conditions: Column: - material: stainless steel - length: 2 m - internal diameter: 2 mm - packing material: appropriate molecular sieve capable of absorbing molecules with diameters up to 0.5 nm. Carrier: - gas: helium (not less than 99.995 % (v/v) of He) - flow: 40 ml/min Detector: thermal conductivity detector Injector: loop injector Column temperature: 50� Detector temperature: 130� Reference gas (a): ambient air Reference gas (b): Nitrogen (not less than 99.999 % (v/v) of N2, less than 1 ppm CO, less than 5 ppm O2) Procedure: Inject reference gas (a). Adjust the injected volumes and operating conditions so that the height of the peak due to nitrogen in the chromatogram is at least 35 % of full scale of the recorder. The assay is not valid unless the chromatograms obtained show a clear separation of oxygen and nitrogen. Inject the gas to be examined and the reference gas (b). In the chromatogram obtained with the gas to be examined, the area of the principal peak is at least 99.0 % of the area of the principal peak in the chromatogram obtained with reference gas (b). |