A: Evaporate a volume of Injection, equivalent to about 500 mg of ioxilan, to dryness. Char the residue so obtained in a suitable crucible: violet vapors are evolved (presence of iodine).

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

Standard stock solution, Internal standard solution, Standard solutions A, B, C, D, and Chromatographic system— Proceed as directed in the test for Residual methanol under Ioxilan.

Test solution— Transfer an accurately measured volume of Injection, equivalent to about 1 g of ioxilan, to a 10-mL volumetric flask. Add 1.0 mL of Internal standard solution, dilute with water to volume, and mix.

Procedure— Proceed as directed for Procedure in the test for Residual methanol under Ioxilan: not more than 0.005% is found.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and water (87:13). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation A— Transfer about 60 mg of USP Ioxilan RS, to a 10-mL volumetric flask, and add 1 mL of water. [note—Heat gently, if necessary, to effect dissolution. Cool to room temperature before proceeding.] Dilute with acetonitrile to volume, and mix.

Standard preparation B— Prepare a 1 in 10 dilution of Standard preparation A in Mobile phase.

Assay preparation A— Transfer an accurately measured volume of Injection, equivalent to about 60 mg of ioxilan, to a 10-mL volumetric flask, add 1 mL of water, and swirl to mix. Dilute with acetonitrile to volume, and mix.

Assay preparation B— Prepare a 1 in 10 dilution of Assay preparation A in Mobile phase.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 245-nm detector and a 25-cm × 4.6-mm stainless steel column that contains packing L8. The column is maintained at 30, and the flow rate is about 1 mL per minute. Chromatograph Standard preparation A, and record the peak responses as directed under Procedure: the resolution, R, between the two largest impurity peaks eluting immediately after the second ioxilan isomer peak is not less than 0.3. Chromatograph Standard preparation B, and record the peak responses as directed under Procedure: the resolution, R, between the two ioxilan isomer peaks is not less than 2.2, the column efficiency, based on the larger ioxilan isomer peak, is not less than 4000 theoretical plates, and the relative standard deviation of the sums of the responses of the two ioxilan isomer peaks from replicate injections is not less than 2.0%.

Procedure— Separately inject equal volumes (about 10 µL) of Assay preparation A, Assay preparation B, Standard preparation A, and Standard preparation B into the chromatograph, record the chromatograms, and measure the areas of the responses for the major peaks. Record the integrated results, summing the areas of the two ioxilan peaks. From the chromatogram of Assay preparation A in comparison to that of Standard preparation B, determine the quantity of ioxilan in the Injection taken. Determine the percentage of impurities (excluding the serinol impurity with a relative retention time of 0.9 relative to the larger ioxilan isomer peak) by area percent, using the chromatogram of Assay preparation A. Not more than 0.5% of any individual impurity is found, and the total of all impurities is not more than 1.5%. [note—The impurities eluting on the tail of the second ioxilan isomer peak should be integrated by skimming the peaks.]