A:Infrared Absorption á197Kñ.

B:Ultraviolet Absorption á197Uñ—

Test solution: 10mg per mL,in chloroform.

Mobile phase— Dissolve 27.2g of monobasic potassium phosphate in 1000mLof water,adjust with phosphoric acid to a pHof 2.4,and mix.Prepare a filtered and degassed mixture of this solution and acetonitrile (90:10).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability standard solution— Dissolve an accurately weighed quantity of USP Ofloxacin RSin methanol to obtain a solution having a known concentration of about 1.0µg per mL.

Test solution— Quantitatively dissolve an accurately weighed quantity of Ofloxacin in methanol to obtain a solution containing about 1.0mg per mL.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 294-nm detector and a 4.6-mm ×10-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph the System suitability standard solution,and record the peak responses as directed for Procedure:the column efficiency,determined from the ofloxacin peak,is not less than 1400theoretical plates when calculated by the formula: and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Inject a volume (about 10µL)of the Test solutioninto the chromatograph,record the chromatogram for a period of time that is 2.5times the retention time of the main ofloxacin peak,and measure the areas for all the peaks,except to disregard the solvent peak.Calculate the percentage of desfluoroofloxacin in the portion of Ofloxacin taken by the formula: in which 1.13is the response factor of desfluoroofloxacin relative to that of ofloxacin;rdis the area for the desfluoroofloxacin peak,if present,at a retention time of about 0.56relative to that of ofloxacin;and rtis the total area of the peaks,except for the solvent peak:not more than 0.2%is found.Calculate the percentage of each other impurity with an area greater than that of the ofloxacin peak in the chromatogram of the System suitability standard solutionobtained under Chromatographic system,by the formula: in which riis the peak area for an individual impurity;and rtis the total area of the peaks in the chromatogram obtained from the Test solution,except for the solvent peak:not more than 0.3%of any individual impurity is found;and the sum of all impurities found is not more than 0.5%.

Internal standard solution— Prepare a solution in sodium hydroxide solution (1in 100)containing 0.7µLof n-propyl alcohol per mL.Transfer 2.0mLof this solution to a 250-mLvolumetric flask,dilute with the same sodium hydroxide solution (1in 100)to volume,and mix.

Standard solution— Prepare a solution in Internal standard solutioncontaining 10.0µg each of methanol and dehydrated alcohol per mL.Transfer 2.0mLof this solution to a vial fitted with a septum and crimp cap,and seal.Heat the sealed vial at 90for 2minutes,and shake for 6minutes.

Test solution— Transfer 40mg of Ofloxacin,accurately weighed,to a vial fitted with a septum and a crimp cap,add 2.0mLof Internal standard solution,and seal the vial.Heat the sealed vial at 90for 2minutes,and shake for 6minutes.

Blank— Transfer 2.0mLof the Internal standard solutionto a vial fitted with a septum and crimp cap,and seal.Heat the sealed vial at 90for 2minutes,and shake for 6minutes.

Chromatographic system (see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector,a 0.53-mm ×30-m fused silica column coated with a 3.0-µm film of stationary phase G43,and a fused silica precolumn.Helium is used as the carrier gas at a flow rate of about 7mLper minute.The injection port and detector temperatures are maintained at about 170and 250,respectively.Condition the column with the helium flowing at 200for 2hours or until a stable baseline is obtained.For analysis,the column temperature is programmed according to the following steps.It is maintained at 35for 3minutes,then increased to 90at a rate of 20per minute,then increased further to 200at a rate of 40per minute,and then maintained for 2minutes.Chromatograph the headspace of the Standard solution,and record the peak responses as directed for Procedure:the relative retention times are about 0.5for methanol,0.6for ethanol,and 1.0for n-propyl alcohol;the resolution,R,between the methanol peak and the ethanol peak is not less than 2.0;and the relative standard deviation for replicate injections is not more than 5%.

Procedure— Use a heated gas tight syringe to make injections of the headspace into the chromatograph.Separately inject equal volumes (about 1mL)of the headspace of the Standard solution,the Blank,and the Test solutioninto the chromatograph,record the chromatograms,and measure the peak area responses.Calculate the percentage of methanol and ethanol in the Ofloxacin taken by the formula: in which Wis the weight,in mg,of Ofloxacin taken to prepare the Test solution;and RU,RB,and RSare the peak response ratios of the relevant alcohol peak to the internal standard peak obtained from the Test solution,the Blank,and the Standard solution,respectively:not more than 0.005%of methanol and not more than 0.05%of ethanol are found.