Change to read:

Change to read:

A: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.USP28

B: It responds to the tests for Sulfate á191ñ.

Test solution: 30mg per mL,in water.

Add the following:

Dilute phosphoric acid,Mobile phase,Resolution solution,Assay preparation,and Chromatographic system— Proceed as directed in the Assay.

Test solution— Use the Assay preparation.

Reference solution— Transfer 1.0mLof the Test solutionto a 100-mLvolumetric flask,dilute with Mobile phase to volume,and mix.

Procedure— Separately inject equal volumes (about 20µL)of the Test solutionand the Reference solutioninto the chromatograph,and measure the area responses for all the peaks,except those due to the solvent.Calculate the percentage of each impurity in the portion of Netilmicin Sulfate taken by the formula: in which riis the peak response of each impurity in the chromatogram obtained from the Test solution,and rSis the netilmicin peak response in the chromatogram obtained from the Reference solution:not more than 1%of any individual impurity is found,and not more than 5%of total impurities is found.USP28

Change to read:

Dilute phosphoric acid— Dilute 5.0mLof phosphoric acid to 1000mLwith water,and mix.

Mobile phase— Dissolve 20.22g of sodium heptanesulfonate in Dilute phosphoric acid,dilute with Dilute phosphoric acidto 1000mL,and mix.To 620mLof this solution add 380mLof acetonitrile,mix,and pass through a filter having a 0.45-µm porosity.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Resolution solution— Prepare a solution in Mobile phasecontaining about 1mg of USP Netilmicin Sulfate RSand 1mg of USP Sisomicin Sulfate RSper mL.

Standard preparation— Transfer about 50mg of USP Netilmicin Sulfate RSto a low-actinic,previously accurately tared,50-mLvolumetric flask.Place the flask in a vacuum desiccator under a vacuum of less than 5mm of mercury for 1hour.Accurately weigh the flask,and determine the dry weight of the USP Netilmicin Sulfate RStaken.Dissolve in and dilute with Mobile phaseto volume,and mix.

Assay preparation— Transfer about 50mg of Netilmicin Sulfate to a low-actinic,previously accurately tared,50-mLvolumetric flask.Place the flask in a vacuum desiccator under a vacuum of less than 5mm of mercury for 1hour.Accurately weigh the flask,and determine the dry weight of the Netilmicin Sulfate taken.Dissolve in and dilute with Mobile phaseto volume,and mix.

Chromatographic system— (see Chromatography á621ñ)—The chromatograph is equipped with a 205-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed for Procedure:the resolution,R,between sisomicin and netilmicin is not less than 1.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 3000theoretical plates;the tailing factor is not more than 2;and the relative standard deviation for replicate injections is not more than 1%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,and measure the area responses for the main peaks.Calculate the quantity,in µg,of netilmicin (C21H41N5O7)per mg of Netilmicin Sulfate taken by the formula: in which WSis the dry weight,in mg,of USP Netilmicin Sulfate RStaken to prepare the Standard preparation;Pis the designated potency,in µg of netilmicin (C21H41N5O7)per mg,of the USP Netilmicin Sulfate RS;WUis the dry weight,in mg,of the Netilmicin Sulfate taken to prepare the Assay preparation;and rUand rSare the netilmicin peak responses obtained from the Assay preparationand the Standard preparation,respectively.USP28