Change to read:

Buffer solution,Solution A,Solution B,Mobile phase,and Standard preparation— Proceed as directed in the Assayunder Atracurium Besylate.

System suitability solution— Heat a portion of the Standard preparationat 90for 30minutes,and chill immediately to about 5.

Diluted standard preparation— Dilute a portion of the Standard preparationquantitatively,and stepwise if necessary,with Solution Ato obtain a solution having a known concentration of about 0.02mg per mL.

Test preparation— Use the Assay preparation.

Chromatographic system— Prepare as directed for Chromatographic systemin the Assay.Chromatograph the System suitability solutionand the Diluted standard preparation,record the chromatograms,and measure the responses for the degradation products by comparing the peak responses of the System suitability solutionto those of the Diluted standard preparationas directed for Procedure:the retention times relative to the atracurium besylate cis-cis-isomer are about 0.22for the acidic compound;0.29for laudanosine;0.44and 0.50for the trans-and cis-isomers,respectively,of the hydroxy compound;and about 1.28and 1.33for the trans-and cis-isomers,respectively,of the monoacrylate.

Procedure— Separately inject equal volumes (about 20µL)of the Diluted standard preparationand the Test preparationinto the chromatograph,record the chromatograms,and measure the peak responses,except the peak due to benzenesulfonic acid occurring at a retention time of about 0.08relative to the atracurium besylate cis-cis-isomer.Calculate the percentage of each impurity in the portion of Test preparationtaken by the formula: in which Cis the concentration,in mg per mL,of USP Atracurium Besylate RSin the Diluted standard preparation;Mis the concentration of atracurium besylate,in mg per mL,in the Test preparation;riis the peak response for each impurity obtained from the Test preparation;and rsis the sum of the responses of all the peaks obtained from the Diluted standard preparation:not more than 6.0%of the acidic compound,not more than 6.0%of the combined cis-and trans-isomers of the hydroxy compound,not more than 3.0%of laudanosine,not more than 3.0%of the combined cis-and trans-isomers of the monoacrylate,and not more than 2.0%of other known impuritiesUSP28is found;not more than 0.1%of any other impurity is found;and not more than 15.0%of total impurities is found.

Change to read:

Buffer solution,Solution A,Solution B,Mobile phase,and Standard preparation— Proceed as directed in the Assayunder Atracurium Besylate.

Assay preparation— Transfer an accurately measured volume of Injection,equivalent to about 50mg of atracurium besylate,to a 50-mLvolumetric flask,dilute with Solution Ato volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm ×25-cm column that contains base-deactivated packing L1.The flow rate is about 1mLper minute.The chromatograph is programmed as follows. Chromatograph replicate injections of the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.8for the atracurium besylate trans-trans-isomer,0.9for the cis-trans-isomer,and 1.0for the cis-cis-isomer;the resolution,R,between the atracurium besylate trans-trans-isomer and the cis-trans-isomer and between the atracurium besylate cis-trans-isomer and the cis-cis-isomer is not less than 2.0;and the relative standard deviation for replicate injections is not more 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 three atracurium besylate isomer peaks.Calculate the quantity,in mg,of atracurium besylate (C65H82N2O18S2)in each mLof the Injection taken by the formula: USP28in which Cis the concentration,in mg per mL,of USP Atracurium Besylate RSin the Standard preparation;Vis the volume,in mL,of Injection taken for the Assay preparation;and rUand rSare the sums of the peak responses of the atracurium besylate trans-trans,trans-cis,and cis-cis-isomers obtained from the Assay preparationand the Standard preparation,respectively.