Identification—
A:
Place a volume of Oral Solution, equivalent to about 500 mg of aminophylline, in a suitable container, and add, with constant stirring, 1 mL of 3 N hydrochloric acid or an amount sufficient to precipitate the theophylline completely. Filter (retain the filtrate), wash the precipitate with small portions of cold water until free from chloride, and dry at 105
for 1 hour: the theophylline so obtained melts between 270
and 274
.
Ethylenediamine content—
Accurately measure a volume of Oral Solution, equivalent to about 500 mg of aminophylline, and dilute with water, if necessary, to make about 30 mL. Add
methyl orange TS, and titrate with 0.1 N hydrochloric acid VS. Each mL of 0.1 N hydrochloric acid is equivalent to 3.005 mg of C
2H
8N
2. The Oral Solution contains between 176 mg and 283 mg of ethylenediamine (C
2H
8N
2) per g of C
7H
8N
4O
2 found in the
Assay.
Assay—
Mobile phase, Diluent, Standard preparation, Resolution solution, and Chromatographic system—
Prepare as directed in the
Assay under
Aminophylline.
Assay preparation—
Transfer an accurately measured volume of Oral Solution, equivalent to about 18 mg of anhydrous theophylline, to a 250-mL volumetric flask, dilute with Diluent to volume, and mix.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Aminophylline. Calculate the quantity, in mg, of theophylline (C
7H
8N
4O
2) in each mL of the Oral Solution taken by the formula:
250(C / V)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Theophylline RS in the
Standard preparation; V is the volume, in mL, of Oral Solution taken; and
rU and
rS are the theophylline peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
791
:
between 8.5 and 9.7.