Mobile phase— Prepare a mixture of methanol and 0.05Mmonobasic ammonium phosphate (64:36).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability preparation— Proceed as directed in the Assayunder Lorazepam Injection.

Standard solution— Prepare a solution in Mobile phasehaving known concentrations of about 3.2µg each of USP Lorazepam Related Compound C RSand USP Lorazepam Related Compound D RS,and 0.16µg of USP Lorazepam Related Compound B RSper mL.

Test solution— Transfer an accurately measured volume of Oral Concentrate,equivalent to about 4mg of lorazepam,to a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix to obtain a solution having a known concentration of about 0.16mg per mL.

Chromatographic system— Proceed as directed in the Assayunder Lorazepam Injection,except that the flow rate is 0.7mLper minute.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses of any peaks other than the lorazepam peak.Do not include as an impurity any peak observed in the chromatogram of the Test solutionthat has a retention time shorter than that of the lorazepam related compound Dpeak in the Standard solution.Calculate the percentages of lorazepam related compound B,lorazepam related compound C,and lorazepam related compound Dtaken by the formula: in which CSis the concentration,in µg per mL,of the corresponding component in the Standard solution;CUis the concentration,in µg per mL,of lorazepam in the Test solution;rUis the peak response of lorazepam related compound B,lorazepam related compound C,or lorazepam related compound Din the chromatogram obtained from the Test solution;and rSis the peak response of the corresponding component in the Standard solution.Not more than 0.1%of lorazepam related compound Bis found;and not more than 4.0%for the sum of lorazepam related compound Cand lorazepam related compound Dis found.

Mobile phase— Prepare a mixture of water,acetonitrile,and glacial acetic acid (55:45:0.2).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability preparation —Dissolve 10mg each of Lorazepam and USP Lorazepam Related Compound E RSin 100mLof methanol.

Standard preparation— Dissolve an accurately weighed quantity of USP Lorazepam RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a known concentration of about 0.05mg per mL.

Assay preparation— Transfer an accurately measured volume of Oral Concentrate,equivalent to 5mg of lorazepam,to a 100-mLvolumetric flask,and dilute with methanol to volume to obtain a solution containing about 0.05mg of lorazepam per mL.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation is not more than 2.0%.Chromatograph the System suitability preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.6for lorazepam and 1.0for lorazepam related compound E;and the resolution,R,between lorazepam and lorazepam related compound Eis not less than 2.0.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of lorazepam (C15H10Cl2N2O2)in the portion of Oral Concentrate taken by the formula: in which Cis the concentration,in mg per mL,of USP Lorazepam RSin the Standard preparation;and rUand rSare the lorazepam peak responses obtained from the Assay preparationand the Standard preparation,respectively.