Butane
C4H10 58.12

n-Butane [106-97-8].
»Butane contains not less than 97.0percent of n-butane (C4H10).
[Caution—Butane is highly flammable and explosive. ]
Packaging and storage— Preserve in tight cylinders,and prevent exposure to excessive heat.
Identification—
A: The IRabsorption spectrum of it exhibits maxima,among others,at about the following wavelengths,in µm:3.4(vs),6.8(s),7.2(m),and 10.4(m).
B: The vapor pressure of a test specimen,obtained as directed in the General Sampling Procedure underPropellants (seeAerosols,Metered-Dose Inhalers,and Dry Powder Inhalers á601ñ),determined at 21by means of a suitable pressure gauge,is between 205and 235kPa absolute (30and 34psia).
Water: not more than 0.001%,determined as directed for Water Content underAerosols,Nasal Sprays,Metered-Dose Inhalers,and Dry Powder Inhalers á601ñ.
High-boiling residues: not more than 5µg per mL,determined as directed for High-Boiling Residues,Method II,underAerosols,Nasal Sprays,Metered-Dose Inhalers,and Dry Powder Inhalers á601ñ.
Acidity of residue— Add 10mLof water to the residue obtained in the test for High-boiling residues,mix by swirling for about 30seconds,add 2drops of methyl orange TS,insert the stopper in the tube,and shake vigorously:no pink or red color appears in the aqueous layer.
Limit of sulfur compounds— 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:the odor is free from the characteristic odor of sulfur compounds.
Assay—
Chromatographic system— Under typical conditions,the gas chromatograph is equipped with a thermal-conductivity detector and contains a 3-mm ×6-m aluminum column packed with 10weight percent of liquid phase G30on nonacid-washed support S1C,helium is used as the carrier gas at a flow rate of 50mLper minute,and the temperature of the column is maintained at 33.
System suitability— The peak responses obtained for n-butane in the chromatograms from duplicate determinations agree within 1%.
Procedure— Connect 1Butane cylinder to the chromatograph through a suitable sampling valve and a flow control valve downstream from the sampling valve.Flush the liquid specimen through the sampling valve,taking care to avoid entrapment of gas or air in the sampling valve.Inject a suitable volume,typically 2µL,of Butane into the chromatograph,and record the chromatogram.Calculate the percentage purity by dividing 100times the n-butane response by the sum of all of the responses in the chromatogram.
Auxiliary Information— Staff Liaison:Kahkashan Zaidi,Ph.D.,Senior Scientific Associate
Expert Committee:(AER)Aerosols
USP28–NF23Page 2967
Phone Number:1-301-816-8269