A: Dilute about 5 mL with 20 mL of water, and add 1.0 mL of 2 N sodium hydroxide and 2 drops of potassium permanganate TS: a green color is produced.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation obtained as directed in the Assay.

C: Transfer a portion of Injection, equivalent to about 100 mg of dyphylline, to a 200-mL volumetric flask, dilute with water to volume, and mix. Transfer 2 mL to a 100-mL volumetric flask, dilute with water to volume, and mix: the UV absorption spectrum of the solution exhibits maxima and minima at the same wavelengths as that of a solution of USP Dyphylline RS containing 10 µg per mL, concomitantly measured.

Mobile phase, Standard preparation, and Chromatographic system— Prepare as directed in the Assay under Dyphylline Tablets.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 100 mg of dyphylline, to a 500-mL volumetric flask, add water to volume, and mix.

Procedure— Proceed as directed in the Assay under Dyphylline Tablets. Calculate the quantity, in mg, of C10H14N4O4 in each mL of the Injection taken by the formula: in which V is the volume, in mL, of Injection taken, and the other terms are as defined therein.