Test specimen— Stir a portion of finely powdered Tablets,equivalent to about 15mg of lorazepam,with 40mLof acetone for 5minutes.Pass through very retentive filter paper pre-washed with acetone.Evaporate the filtrate on a steam bath with the aid of a current of air to dryness.Dissolve the residue in 1mLof acetone,and add 20mLof 2,2,4-trimethylpentane.Heat the solution on a hot plate to a gentle boil,and evaporate to a volume of about 10mL.Remove the solution from the hot plate,and evaporate with the aid of a current of air to dryness.Dry the residue in vacuum at 60for 1hour.

Diluent,Mobile phase,andChromatographic system— Prepare as directed in the Assay.

Standard solution— Prepare as directed for Standard preparationin the Assay.

Test solution— Place 1Tablet in a volumetric flask of appropriate size,based on the labeled quantity,in mg,of lorazepam in the Tablet,to obtain a solution having a concentration of about 0.1mg of lorazepam per mL.Add a volume of Diluentequal to about 50%of the volume of the flask,sonicate for 10minutes,and shake by mechanical means for 20minutes.Dilute with Diluentto volume,mix,and centrifuge a portion of the solution for 10minutes at 2000rpm.

Procedure— Separately inject equal volumes (about 20µL)of the Test solutionand the Standard solutioninto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of lorazepam (C15H10Cl2N2O2)in the Tablet taken by the formula: in which Tis the labeled quantity,in mg,of lorazepam in the Tablet;Cis the concentration,in mg per mL,of USP Lorazepam RSin the Standard solution;Dis the concentration,in mg per mL,of lorazepam in the Test solution,based on the labeled quantity per Tablet and the extent of dilution;and rUand rSare the lorazepam peak responses obtained from the Test solutionand the Standard solution,respectively.

Standardpreparation	Dilution	Concentration (µg of each RSper mL)	Percentage (%,for comparison with test specimen)
A	(1in 25)	40	2.0
B	(1in 50)	20	1.0
C	(1in 100)	10	0.5

Test preparation— Transfer a quantity of finely powdered Tablets,equivalent to 4.0mg of lorazepam,to a sintered-glass funnel.Extract with two 1-mLportions of chloroform followed by two 1-mLportions of methanol,collecting the filtrate in a centrifuge tube.Evaporate the filtrate with the aid of a stream of nitrogen at room temperature to dryness.Dissolve the residue in 2.0mLof chloroform,and centrifuge.Use the clear supernatant as the Test preparation.

Procedure— Within 30minutes after preparation,apply separately 50µLof the Test preparationand 50µLof each Standard preparationto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture and previously washed with a mixture of chloroform,ethyl acetate,and methanol (2:1:1)and dried in air.Allow the spots to dry,and develop the chromatograms in a solvent system consisting of a mixture of chloroform,dioxane,and glacial acetic acid (91:5:4)until the solvent front has moved to within 2cm to 3cm from the top of the plate.Remove the plate from the developing chamber,mark the solvent front,and allow to air-dry for about 30minutes.Examine the plate under short-wavelength UVlight.Compare the intensities of any secondary spots observed in the chromatogram of the Test preparationwith those of the principal spots in the chromatograms of the Standard preparations:[NOTE—The RFvalue and the intensity of the spot for the USP Lorazepam Related Compound E RSin the Standard preparationscorrespond closely,but not necessarily precisely,to those observed for one of the secondary spots observed in the chromatogram of the Test preparation.]The sum of the intensities of all secondary spots obtained from the Test preparationcorresponds to not more than 4.0%.

100(C/20)(VU/V)(rU/rS),