Packaging and storage—
Preserve in tight, light-resistant containers, and avoid exposure to excessive heat.
Identification—
A:
The IR absorption spectrum of a 1 in 20 solution in chloroform exhibits maxima only at the same wavelengths as that of a similar solution of
USP Methoxyflurane RS.
B:
To 1 mL in a test tube add 1 mL of sulfuric acid: the specimen forms a layer over the acid (distinction from halothane).
C:
Cautiously heat the contents of the test tube from
Identification test
B with agitation: the interface disappears, and hydrofluoric acid is evolved (
distinction from chloroform,
trichloroethylene,
and halothane).
Acidity—
Shake 25 mL with 25 mL of carbon dioxide-free water for 2 minutes, and allow the layers to separate. Add 1 drop of
methyl red TS to the water extract, boil for 1 minute, and titrate with 0.010 N sodium hydroxide: not more than 0.50 mL of 0.010 N sodium hydroxide is required to produce a distinct yellow color.
Foreign odor—
Place 10 mL on a dry watch glass, and allow it to evaporate spontaneously to about 1 mL: no foreign odor is perceptible during the evaporation. To the remaining test specimen add a piece of odorless filter paper, and allow the paper to dry, checking it for foreign odor every few seconds during the drying period. As the last traces of odor leave the paper, a faint, characteristic odor may be detected for a few seconds, but no residual foreign odor is detected.
Limit of nonvolatile residue—
Allow 50 mL to evaporate at room temperature in a tared evaporating dish, and dry the residue at 105
for 1 hour: the weight of the residue does not exceed 1 mg.
Assay—
Inject a volume of Methoxyflurane (30 µL or less) into a suitable gas chromatograph (see
Chromatography 
621
) equipped with a thermal conductivity detector. Under typical conditions, the instrument contains a 4-mm × 3-m stainless steel column packed with liquid phase G11 on support S1A, the column is maintained at a temperature of 100
to 110
, the injection port is maintained at about 150
, and dry helium is used as the carrier gas at a flow rate of about 60 mL per minute. Calculate the percentage purity by dividing 100 times the area of the methoxyflurane peak by the sum of all the areas in the chromatogram.
Auxiliary Information—
Staff Liaison :
Daniel K. Bempong, Ph.D., Scientist
Expert Committee : (MDPS05) Monograph Development-Pulmonary and Steroids
USP29–NF24 Page 1387
Pharmacopeial Forum : Volume No. 31(5) Page 1388
Phone Number : 1-301-816-8143
;)
