A: Infrared Absorption á197Kñ.

B: The RFvalue of the principal spot in the chromatogram,developed with the Basic eluant,obtained from the Test solutioncorresponds to that obtained from the Standard solutionin the Ordinary impuritiestest.

Test solution— Transfer an accurately weighed quantity,about 1.00g of Iopromide,to a 20-mLvolumetric flask,dissolve in and dilute with water to volume,and mix.Pipet 12.0mLof this solution into a test tube,add 2.0mLof pH3.5Acetate Buffer,and mix.

Standard solution— Pipet 1.0mLof Standard Lead Solution(10µg of lead),into a test tube,add 9.0mLof water,2.0mLof the Test solution,and 2.0mLof pH3.5Acetate Buffer,and mix.

Thioacetamide-glycerin base solution color-comparison tubes— Mix 15mLof 1Nsodium hydroxide and 5mLof water,and add 20mLof glycerin.Pipet 1.0mLof this solution and 0.20mLof thioacetamide TSinto each of two color-comparison test tubes,and heat in a boiling water bath for 20seconds.Use these tubes immediately.

Procedure— Immediately add the Test solutionto one of the Thioacetamide-glycerin base solution color-comparison tubesand the Standard solutionto the other.Mix,allow to stand for 2minutes,and view downward over a white surface:the color of the solution from the Test solutionis not darker than that of the solution from the Standard solution,treated in the same manner.

Test solution— Transfer 500mg of Iopromide to a 25-mLvolumetric flask,add 20mLof water,and mix.

Standard solution— Dissolve a suitable quantity of USP Iopromide Related Compound A RSin water,and dilute with water to obtain a stock solution having a known concentration of 0.25mg per mL.Transfer 2.0mLof this stock solution to a 25-mLvolumetric flask,add 18.0mLof water,and mix.

Blank solution— Transfer 20mLof water to a 25-mLvolumetric flask.

Procedure— Treat each flask as follows.Place the flasks in an ice bath,and protect from light.Add slowly 1.0mLof 8Nhydrochloric acid,mix,and allow to stand for 5minutes.Add 1.0mLof sodium nitrite solution (1in 50),mix,and allow to stand for 5minutes.Add 0.50mLof freshly prepared sulfamic acid solution,(8in 100).Shake each flask vigorously several times within the next 5minutes,venting off the gas that evolves.[Caution—Considerable pressure is produced. ]Add 1.0mLof freshly prepared N-(1-naphthyl)ethylenediamine dihydrochloride solution,(1in 1000)in a mixture of propylene glycol and water (70:30),and shake.Remove the flasks from the ice bath,and allow to stand in a water bath at about 25for 10minutes.Dilute with water to volume,mix,and degas with the aid of sonication for 1minute.Concomitantly determine the absorbances of the Test solutionand the Standard solutionin 1-cm cells at the wavelength of maximum absorbance at about 495nm,with a suitable spectrophotometer,using the Blank solution,treated in the same manner.The absorbance of the Standard solutionis not less than 0.40.Calculate the percentage of free aromatic amine in the portion of Iopromide taken by the formula: in which WSis the quantity,in mg,of USP Iopromide Related Compound A RStaken to prepare the Standard solution;WUis the quantity,in mg,of the Iopromide taken to prepare the Test solution;and AUand ASare the absorbances of the Test solutionand the Standard solution,respectively:not more than 0.1%is found.

Standard solution— Prepare a solution of alcohol in dimethylformamide to obtain a solution having a known concentration of about 0.050mg of alcohol (C2H5OH)per mL.

Test solution— Dissolve an accurately weighed portion of Iopromide in dimethylformamide to obtain a concentration of about 50mg per mL.

Blank solution— Use dimethylformamide.

Chromatographic system (see Chromatography á621ñ)—The gas chromatograph is equipped with a headspace injector,a flame-ionization detector,and a 0.25-mm ×30-m capillary column,the internal wall of which is coated with a 1.4-µm film of liquid phase G43.The column temperature is programmed according to the following steps:it is held at 40for 10minutes,then increased at a rate of 5per minute to 70;it is then increased at a rate of 30per minute to 220.The injector port is maintained at 160;the headspace sampler is maintained at 80;and the detector is maintained at 250.Helium is used as the carrier gas at a flow rate of about 27cm per second.Chromatograph the Standard solution,and record the peak responses as directed for Procedure:the retention time for alcohol is about 3minutes;and the relative standard deviation for three injections of the Standard solutionis not more than 4.0%.Chromatograph the Blank solution,and record the peak responses as directed for Procedure:the chromatogram shows no peak at the retention time for alcohol.

Procedure— [NOTE—Use peak areas where peak responses are indicated.]Transfer 2.0mLeach of the Test solution,the Standard solution,and the Blank solutionto separate headspace vials,add 10µLof 1Nhydrochloric acid to each vial,then seal the vials using a flanged cap so that the cap can no longer be turned.Record the chromatograms,and measure the responses for the alcohol peak.Calculate the concentration of alcohol in the portion of Iopromide taken by the formula: in which Cis the concentration,in mg per mL,of alcohol (C2H5OH)in the Standard solution;Iis the quantity,in mg per mL,of Iopromide in the Test solution;and rUand rSare the alcohol peak responses in the chromatograms obtained from the Test solutionand the Standard solution,respectively:not more than 0.4%of alcohol (C2H5OH)is found.Use the percentage obtained to calculate the Assayresult on the solvent-free basis.

20(WB/WI)[(AY1+AY2)/(RY1+RY2)],

Test solution: a mixture of methanol and water (1:1).

Standard solutions: a mixture of methanol and water (1:1).

Visualization solution—

SOLUTIONA —Dissolve 2.7g of ferric chloride in 100mLof 2.4Nhydrochloric acid.Store this solution in a refrigerator.

SOLUTIONB —Dissolve 3.5g of potassium ferricyanide in 100mLof water.Store this solution in a refrigerator.

SOLUTIONC —Dissolve 5.0g of sodium arsenite in 30mLof 1Nsodium hydroxide solution that has been cooled to 0.While stirring,mix with 65mLof 2.4Nhydrochloric acid,and store at room temperature.Use the clear supernatant.

Procedure —Mix 10mLof Solution A,10mLof Solution B,and 2.0mLof Solution C.Use within 30minutes.

Basic eluant: a mixture of dioxane,water,and ammonium hydroxide (85:15:4).

Acidic eluant: a mixture of chloroform,methanol,water,and 96percent formic acid (62:32:6:2).

Procedure— Apply 1µLand 2µLof the Test solutionand 1µLof each of the Standard solutionsto two separate thin-layer chromatographic plates.Place one plate in a development chamber containing the Acidic eluant,and the second plate in a development chamber containing the Basic eluant.After the chromatograms have developed,remove the plates from the chambers,and allow to dry at room temperature.

Visualization—

DETECTION 1—Observe both plates under 254-nm UVlight.

DETECTION 2—The plate developed with the Acidic eluantis exposed to ammonia vapors for 10to 30minutes and is air dried.Both plates are exposed to unfiltered 254-nm UVlight for several minutes until the principal spots appear yellow.Overspray with Visualization solution,and examine the plates under ambient light.Determine the percentage of all secondary spots,except those due to free aromatic amine and to the N-acetyl compound.

Limit— The sum of all secondary spots observed in the chromatograms of the Test solution,except those due to the free aromatic amine and to the N-acetyl compound in addition to the percentage of N-acetyl compound obtained in the test for Limit of N-Acetyl compound,corresponds to not more than 3.0%.

Solvent: dimethylformamide.

100(rE1+rZ1)/(rE1+rE2+rZ1+rZ2),

100(rE2+rZ2)/(rE1+rE2+rZ1+rZ2):

Diluent— Prepare a mixture of methanol and water (1:1).

Mobile phase— [NOTE—Use chloroform,methanol,and water that have been filtered and degassed.]Mix 6g of chloroform with 59g of methanol,then add 900g of water.Store in a sealed container,and do not stir or sparge the Mobile phaseduring use.

Standard preparation— Transfer an accurately weighed quantity of about 38mg of USP Iopromide RS,to a 20-mLvolumetric flask.Dissolve in and dilute with Diluentto volume,and mix.

Related compound Bstandard solution— Transfer about 1.9mg of USP Iopromide Related Compound B RS,accurately weighed,to a 100-mLvolumetric flask.Dissolve in and dilute with Diluentto volume,and mix.

Assay preparation— Transfer about 38mg of Iopromide,accurately weighed,to a 20-mLvolumetric flask.Dissolve in and dilute with Diluentto volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L1.The flow rate is about 1.2mLper minute.The temperature is maintained at a constant temperature of about 20.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times for iopromide E1-isomer,iopromide E2-isomer,iopromide Z1-isomer,and iopromide Z2-isomer are about 0.70,0.75,0.85,and 1.0,respectively;the resolution,R,between iopromide isomers Z1and Z2is not less than 2.0;and the relative standard deviation for replicate injections for total iopromide area is not more than 2.0%.Chromatograph the Related compound Bstandard solution,and measure the area of the peak responses:the relative retention times for the iopromide related compound BY1-and Y2-isomers are about 0.28and 0.31,respectively;and the signal-to-noise ratio for the iopromide related compound BY2-isomer is not less than 20.

Procedure— [NOTE—Use peak areas where peak responses are indicated.]Separately inject equal volumes (about 10µL)of the Standard preparation,the Related compound Bstandard solution,and the Assay preparationinto the chromatograph,and measure the responses for the major peaks.Allow the Mobile phaseto flow for not less than 60minutes between each injection to prevent interference from late-eluting amine peaks.Calculate the quantity of C18H24I3N3O8in the portion of Iopromide taken by the formula: in which Cis the concentration,in mg per mL,of USP Iopromide RSin the Standard preparation,and rUand rSare the sums of the peak responses for iopromide E1-isomer,iopromide E2-isomer,iopromide Z1-isomer,and iopromide Z2-isomer in the chromatograms obtained from the Assay preparationand the Standard preparation,respectively.