A: Infrared Absorption 197K.

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

Buffer solution— Dissolve 790 mg of ammonium carbonate in 1000 mL of water. Adjust, if necessary, with a solution of formic acid (1 in 10) or ammonium hydroxide (1 in 10) to a pH of 8.0 ± 0.05.

Diluent— Prepare a mixture of methanol and water (65:35).

Mobile phase— Prepare a filtered and degassed mixture of methanol and Buffer solution (65:35). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Transfer about 25 mg of USP Altretamine RS, accurately weighed, to a 50-mL volumetric flask. Dissolve in 35 mL of methanol, dilute with water to volume, and mix. Transfer 5.0 mL of this solution to a 50-mL volumetric flask, dilute with Diluent to volume, and mix. This solution contains about 0.05 mg per mL.

Assay preparation— Transfer about 25 mg of Altretamine, accurately weighed, to a 50-mL volumetric flask. Dissolve in 35 mL of methanol, dilute with water to volume, and mix. Transfer 5.0 mL of this solution to a 50-mL volumetric flask, dilute with Diluent to volume, and mix.

Chromatographic system— The liquid chromatograph is equipped with a 227-nm detector and a 4.6-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not greater than 1.5, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C9H18N6 in the portion of Altretamine taken by the formula: in which C is the concentration, in mg per mL, of USP Altretamine RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.