A: Infrared Absorption 197M—

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.

Medium: water; 500 mL.

Apparatus 1: 100 rpm.

Times: 30 minutes; 60 minutes.

Mobile phase and Chromatographic system— Prepare as directed in the Assay.

Procedure— Inject an accurately measured volume (about 50 µL) of a filtered portion of the solution under test into the chromatograph, record the chromatogram, and measure the response for the major peak. Calculate the quantity of C15H10Cl2N2O2 dissolved by comparison of the peak response obtained from a similarly chromatographed Standard solution having a known concentration of USP Lorazepam RS in water. [note—A volume of alcohol not exceeding 10% of the final volume of the Standard solution is used initially to dissolve USP Lorazepam RS.]

Tolerances— The percentage of the labeled amount of C15H10Cl2N2O2 dissolved from the Tablets is not less than 60% (Q) in 30 minutes and not less than 80% (Q) in 60 minutes.

Procedure for content uniformity—

Change to read:

Mobile phase— Prepare a mixture of water, acetonitrile, and glacial acetic acid (50:50:1.2). Make adjustments if necessary (see System Suitability under Chromatography 621).

Buffer— Dissolve 67.7 g of sodium acetate trihydrate in 1 L of water. Adjust with glacial acetic acid to a pH of 5.0 ± 0.05.

Diluent— Prepare a mixture of methanol and Buffer (75:25).

Standard solution— Dissolve an accurately weighed quantity of USP Lorazepam RS in Diluent, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 0.0016 mg per mL of lorazepam.

Peak identification solution— Dissolve accurately weighed amounts of USP Lorazepam RS, USP Lorazepam Related Compound A RS, USP Lorazepam Related Compound B RS, USP Lorazepam Related Compound C RS, USP Lorazepam Related Compound D RS, and USP Lorazepam Related Compound E RS in Diluent to obtain a solution having a final concentration of about 0.16 mg per mL of lorazepam and 1.6 µg per mL each of lorazepam related compound A, lorazepam related compound B, lorazepam related compound C, lorazepam related compound D, and lorazepam related compound E.

Test solution— Grind the number of Tablets required in order to make the total amount of lorazepam in the final composite powder about 25 mg. Accurately weigh and transfer an amount of powder equivalent to about 21.3 mg of lorazepam to a 25-mL volumetric flask. Pipet 20 mL of Diluent into the flask, and stir for 15 minutes. Do not dilute to volume. Centrifuge for 15 minutes at 2000 rpm. Pass the supernatant through a polyethersulfone membrane filter having a porosity of 0.45 µm. Quantitatively dilute the filtrate with Diluent to obtain a final solution having a known concentration of about 0.16 mg per mL of lorazepam, based on the label claim.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a sample compartment chiller maintained at 4, a UV detector set at 230 nm, and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The column temperature is maintained at 5. The flow rate is about 1.0 mL per minute. Chromatograph the Peak identification solution, record the peak responses as directed for Procedure, and identify the peaks, using the retention times given in Table 1. The resolution, R, between lorazepam related compound A and lorazepam related compound E is not less than 1.2. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the tailing factor for lorazepam is not more than 2.0, and the relative standard deviation for replicate injections is not more than 5% for lorazepam.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, collect the data for at least 50 minutes, and measure the responses for all the peaks. Calculate the percentage of each impurity in the portion of Tablets taken by the formula: in which F is the relative response factor for any given impurity found in Table 1; CS is the concentration of lorazepam in the Standard solution; CU is the concentration, in mg per mL, of lorazepam in the Test solution, based on the label claim; ri is the peak response for each impurity obtained from the Test solution; and rS is the peak response for lorazepam obtained from the Standard solution. Table 1 shows the acceptance criteria for each impurity.1S (USP31)

Diluent— Prepare a mixture of methanol and water (17:3).

Mobile phase— Prepare a filtered and degassed mixture of water, acetonitrile, and glacial acetic acid (60:40:0.4). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Lorazepam RS in Diluent, and dilute quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 0.10 mg per mL.

Assay preparation— Transfer 20 Tablets to a 100-mL volumetric flask. Add about 50 mL of Diluent, sonicate for 10 minutes, and shake by mechanical means for 20 minutes. Dilute with Diluent to volume, mix, and centrifuge a portion of the solution for 10 minutes at 2000 rpm. Quantitatively dilute an accurately measured volume of the clear supernatant with Diluent to obtain a solution containing about 0.1 mg of lorazepam per mL.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 230-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. 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 2.0; and the relative standard deviation 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 quantity, in mg, of lorazepam (C15H10Cl2N2O2) in each Tablet taken by the formula: in which C is the concentration, in mg per mL, of USP Lorazepam RS in the Standard preparation; VU is the final volume, in mL, of the Assay preparation; V is the volume, in mL, of the clear supernatant taken to prepare the Assay preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.