Mobile phase— Transfer 14.4 g of sodium lauryl sulfate to a 500-mL volumetric flask, add 100 mL of glacial acetic acid, dilute with water to volume, mix, and pass through a filter having a 0.5-µm or finer porosity. Transfer 50 mL of this solution to a 1000-mL volumetric flask, add 350 mL of methanol and 350 mL of acetonitrile, dilute with water to volume, and mix. Filter and degas before use. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Quantitatively dissolve an accurately weighed quantity of USP Aminopentamide Sulfate RS in water to obtain a solution having a known concentration equivalent to the labeled concentration of aminopentamide sulfate in the Injection.

Assay preparation— Use the undiluted Injection.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1 and is maintained at a constant temperature of about 40. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the tailing factor is not more than 2.5; and the relative standard deviation for replicate injections is not more than 2%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of aminopentamide sulfate (C19H24N2O·H2SO4) in each mL of the Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Aminopentamide Sulfate RS in the Standard preparation; and rU and rS are the aminopentamide peak responses obtained from the Assay preparation and the Standard preparation, respectively.