Mobile phase— Transfer 11 g of sodium 1-pentanesulfonate and 40 g of anhydrous sodium sulfate to a 2-L volumetric flask, and dissolve in about 500 mL of water. Add 20 mL of 1 N sulfuric acid and 30 mL of acetonitrile, dilute with water to volume, and mix. Filter and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Aminocaproic Acid RS in Mobile phase to obtain a solution having a known concentration of about 2.5 mg per mL.

Resolution solution— Mix 20 µL of benzyl alcohol with 100 mL of water. Dilute 1.0 mL of this solution with the Standard preparation to 10 mL.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 1.25 g of aminocaproic acid, to a 50-mL volumetric flask, dilute with water to volume, and mix. Transfer 5.0 mL of the resulting solution to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 210-nm detector and a 4-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the Resolution solution as directed for Procedure: the resolution, R, between benzyl alcohol and aminocaproic acid is not less than 7.0. The aminocaproic acid peak elutes prior to the benzyl alcohol peak. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 50 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 aminocaproic acid (C6H13NO2) in each mL of the Injection taken by the formula: in which C is the concentration, in mg per mL, of USP Aminocaproic Acid RS in the Standard preparation; V is the volume, in mL, of Injection taken; and rU and rS are the aminocaproic acid peak areas obtained from the Assay preparation and the Standard preparation, respectively.