EUROPEAN PHARMACOPOEIA 11.
0 Nitrous oxide
01/2008:1685 Second identification : B, C.
corrected 11.0 A. Examine the chromatograms obtained in the test for
impurities (see Production).
Results : the principal peak in the chromatogram obtained
with the gas to be examined is similar in retention time
to the principal peak in the chromatogram obtained with
NITROGEN, LOW-OXYGEN reference gas (b).
B. In a 250 mL conical flask replace the air by the gas to be
Nitrogenium oxygenio depletum examined. Place a burning or glowing splinter of wood in
the flask. The splinter is extinguished.
N2 Mr 28.01 C. In a suitable test tube, place 0.1 g of magnesium R in
turnings. Close the tube with a two-hole stopper fitted with
DEFINITION a glass tube reaching about 1 cm above the turnings. Pass
This monograph applies to nitrogen which is used for inerting the gas to be examined through the glass tube for 1 min
finished medicinal products which are particularly sensitive without heating, then for 15 min while heating the test tube
to degradation by oxygen. It does not necessarily apply to to a red glow. After cooling, add 5 mL of dilute sodium
nitrogen used in earlier production steps. hydroxide solution R. The evolving vapours turn the colour
Content : minimum 99.5 per cent V/V of N2, calculated by of moistened red litmus paper R blue.
deduction of the sum of impurities found when performing
STORAGE
the test for impurities.
Where the gas has to be stored, store as a compressed gas or
CHARACTERS a liquid in appropriate containers complying with the legal
Colourless and odourless gas. regulations.
Solubility : at 20 °C and at a pressure of 101 kPa, 1 volume IMPURITIES
dissolves in about 62 volumes of water and about 10 volumes
of ethanol (96 per cent). A. O2 : oxygen,
PRODUCTION B. Ar : argon.
Oxygen : maximum 5 ppm V/V, determined using an oxygen 01/2008:0416
analyser with a detector scale ranging from 0 ppm V/V to
100 ppm V/V and equipped with an electrochemical cell.
The gas to be examined passes through a detection cell
containing an aqueous solution of an electrolyte, generally
potassium hydroxide. The presence of oxygen in the gas to be
examined produces variation in the electric signal recorded at NITROUS OXIDE
the outlet of the cell that is proportional to the oxygen content.
Calibrate the analyser according to the manufacturer’s Dinitrogenii oxidum
instructions. Pass the gas to be examined through the analyser
using a suitable pressure regulator and airtight metal tubes N2O Mr 44.01
and operating at the prescribed flow rates until constant [10024-97-2]
readings are obtained.
DEFINITION
Impurities. Gas chromatography (2.2.28).
Content : minimum 98.0 per cent V/V of N2O in the gaseous
Gas to be examined. The substance to be examined. phase, when sampled at 15 °C.
Reference gas (a). Use ambient air.
This monograph applies to nitrous oxide for medicinal use.
Reference gas (b). Use nitrogen R1.
Column : CHARACTERS
– material : stainless steel, Appearance : colourless gas.
– size : l = 2 m, Ø = 2 mm, Solubility : at 20 °C and at a pressure of 101 kPa, 1 volume
– stationary phase : appropriate molecular sieve for dissolves in about 1.5 volumes of water.
chromatography (0.5 nm). PRODUCTION
Carrier gas : helium for chromatography R. Nitrous oxide is produced from ammonium nitrate by thermic
Flow rate : 40 mL/min. decomposition.
Temperature : Examine the gaseous phase.
– column : 50 °C, If the test is performed on a cylinder, keep the cylinder at
– detector : 130 °C. room temperature for at least 6 h before carrying out the tests.
Detection : thermal conductivity. Keep the cylinder in the vertical position with the outlet valve
System suitability : reference gas (a) : adjust the injected uppermost.
volumes and operating conditions so that the height of the Carbon dioxide. Gas chromatography (2.2.28).
peak due to nitrogen in the chromatogram obtained is at least Gas to be examined. The substance to be examined.
35 per cent of the full scale of the recorder : Reference gas. A mixture containing 300 ppm V/V of carbon
– the chromatogram obtained shows a clear separation of dioxide R1 in nitrous oxide R.
oxygen and nitrogen. Column :
Limit : – material : stainless steel ;
– total : not more than 0.5 per cent of the sum of the areas of – size : l = 3.5 m, Ø = 2 mm ;
all the peaks (0.5 per cent V/V).
– stationary phase : ethylvinylbenzene-divinylbenzene
IDENTIFICATION copolymer R.
First identification : A. Carrier gas : helium for chromatography R.
General Notices (1) apply to all monographs and other texts 3527
www.webofpharma.com
