A: Infrared Absorption 197M.

B: The retention times of the two major peaks in the chromatogram of the Assay preparation correspond to those in the chromatogram of the Standard preparation, as obtained in the Assay.

Solution A, Solution B, and Mobile phase— Proceed as directed in the Assay.

Standard solution— Prepare as directed for the Standard preparation in the Assay.

Sensitivity check solution— Dilute the Standard solution with water to obtain a solution having a concentration of 0.25 µg per mL.

Test solution— Prepare as directed for Assay preparation in the Assay.

Chromatographic system— Chromatograph the Sensitivity check solution at 410 nm, and record the peak heights: the ratio of the verteporfin peak height to the noise height is not less than 10, the noise height being determined by a suitable procedure. Proceed as directed in the Assay. To evaluate the system suitability requirements, use the Standard preparation prepared as directed in the Assay.

Procedure— Inject a volume (about 20 µL) of the Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the percentage of each related compound in the portion of Verteporfin taken by the formula: in which ri is the individual peak response of each related compound; and rs is the sum of the responses of all the peaks. Not more than 0.6% of the peak having a retention time of about 0.56 relative to that of the first verteporfin isomer peak is found; not more than 0.8% of any other individual related compound is found; and the sum of all impurities is not more than 4.0%.

Solution A— Prepare a filtered and degassed mixture of 1% (w/v) aqueous ammonium sulfate, acetonitrile, glacial acetic acid, and 3.6 M sulfuric acid (10:10:1:0.027).

Solution B— Prepare a filtered and degassed mixture of 1% (w/v) aqueous ammonium sulfate, tetrahydrofuran, glacial acetic acid, and 3.6 M sulfuric acid (10:10:1:0.034).

Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— To a suitable volumetric flask, transfer an accurately weighed quantity of USP Verteporfin RS sufficient to make a 0.25 mg per mL solution. Add a volume of a mixture of acetonitrile and tetrahydrofuran (1:1) equivalent to 60% of the flask volume, and dissolve. Dilute with water to volume, and mix. [note—Protect the solution from light.]

Assay preparation— Transfer about 25 mg of Verteporfin, accurately weighed, to a 100-mL volumetric flask. Add 60 mL of a mixture of acetonitrile and tetrahydrofuran (1:1), and dissolve. Dilute with water to volume, and mix. [note—Protect the solution from light.]

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 410-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is 1.5 mL per minute. The column temperature is maintained at 30. The chromatograph is programmed as follows. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, between the two verteporfin peaks is not less than 2.5; the tailing factor is not more than 1.3; 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 verteporfin peaks. Calculate the quantity, in mg, of C41H42N4O8 in the portion of Verteporfin taken by the formula: in which C is the concentration, in mg per mL, of USP Verteporfin RS in the Standard preparation; and rU and rS are the sums of the peak responses of the two verteporfin regioisomer peak responses obtained from the Assay preparation and the Standard preparation, respectively.