A: Dissolve about 1 g in 20 mL of warm water, and neutralize the solution with 6 N acetic acid: a white, crystalline precipitate of theophylline is formed. Filter, wash the precipitate with small portions of cold water, and dry it at 105 for 1 hour: the theophylline so obtained melts between 270 and 274, the procedure for Class I being used (see Melting Range or Temperature 741). Retain the remaining portion of the theophylline for use in Identification test B.

B: Infrared Absorption 197K: residue obtained in Identification test A.

C: Ignite it: the residue colors a nonluminous flame intensely yellow and effervesces with acids.

Mobile phase— Prepare a solution containing 470 mg of sodium acetate trihydrate and 1 mL of glacial acetic acid in 2 liters of water. Adjust with 10 N sodium hydroxide to a pH of 4.3. Mix 3 volumes of the resulting solution with 7 volumes of acetonitrile. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Glycine RS in Mobile phase, and dilute quantitatively with Mobile phase to obtain a solution having a known concentration of about 1.3 mg per mL.

Test preparation— Transfer about 153 mg of Theophylline Sodium Glycinate, accurately weighed, to a 50-mL volumetric flask, dissolve in Mobile phase, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 200-nm detector and a 3.9-mm × 30-cm column that contains packing L8. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency determined from the analyte peak is not less than 2000 theoretical plates, the tailing factor for the glycine peak is not more than 2.0, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Test preparation into the chromatograph, record the chromatograms, and measure the responses for the glycine peaks. Calculate the quantity, in mg, of C2H5NO2 in the portion of Theophylline Sodium Glycinate taken by the formula: in which C is the concentration, in mg per mL, of USP Glycine RS in the Standard preparation, and rU and rS are the peak responses obtained from the Test preparation and the Standard preparation, respectively: not less than 42.0 percent and not more than 48.0 percent, on the dried basis, is found.

(Official January 1, 2007)

Buffer solution , Mobile phase, Internal standard solution, Standard preparation, and Chromatographic system—Prepare as directed in the Assay under Theophylline.

Assay preparation— Transfer about 550 mg of Theophylline Sodium Glycinate, previously dried and accurately weighed, to a 250-mL volumetric flask, add about 125 mL of Mobile phase, shake by mechanical means until solution is complete, dilute with Mobile phase to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, add 20.0 mL of Internal standard solution, dilute with Mobile phase to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Theophylline. Calculate the quantity, in mg, of anhydrous theophylline (C7H8N4O2) in the portion of Theophylline Sodium Glycinate taken by the formula: in which the terms are as defined therein.