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.

Mobile phase— Mix 930 mL of water, 3.72 g of dibasic potassium phosphate, and 6.48 g of monobasic potassium phosphate. Add 50 mL of methanol and 20 mL of acetonitrile, and mix. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Cyromazine RS in methanol to obtain a solution having a known concentration of about 0.50 mg per mL. Dilute an aliquot of the resulting solution with Mobile phase to obtain a solution having a known concentration of about 10 µg per mL.

Assay preparation— Dissolve an accurately weighed quantity of Cyromazine in methanol to obtain a solution having a known concentration of about 0.50 mg per mL. Dilute an aliquot of the resulting solution with Mobile phase to obtain a solution having a known concentration of about 10 µg per mL.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 214-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 2.0 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 3000 theoretical plates; 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 Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the content, in percentage, of C6H10N6 in the portion of Cyromazine taken by the formula: in which CS is the concentration, in µg per mL, of USP Cyromazine RS in the Standard preparation; CU is the concentration, in µg per mL, of Cyromazine in the Assay preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.