Aminobenzoate Potassium
»Aminobenzoate Potassium contains not less than 98.5percent and not more than 101.0percent of C7H6KNO2,calculated on the dried basis.
Packaging and storage— Preserve in well-closed containers.
Identification—
Solution: 10µg per mL.
Medium: 0.001Nsodium hydroxide.
B: Dissolve about 400mg in 10mLof water,add 1mLof 3Nhydrochloric acid,filter,and wash the precipitate with two 5-mLportions of cold water.Recrystallize from alcohol the precipitate so obtained,and dry at 110for 1hour:the p-aminobenzoic acid so obtained melts between 186and 189.
C: Asolution (1in 100)meets the requirements of the flame test for Potassium á191ñ.
pHá791ñ: between 8.0and 9.0,in a solution (1in 20).
Loss on drying á731ñ— Dry it at 105for 2hours:it loses not more than 1.0%of its weight.
Volatile diazotizable substances—
Standard preparation— Dissolve 10mg of p-toluidine in 5mLof methanol in a 100-mLvolumetric flask,add water to volume,and mix.Transfer 1mLto a 100-mLvolumetric flask,dilute with water to volume,and mix.
Test preparation— Transfer 5.0g of Aminobenzoate Potassium to a suitable flask,and add a volume of 1.25Nsodium hydroxide that is just sufficient to dissolve the test specimen and to render the solution just alkaline to phenolphthalein TS.Dilute with water to 50mL,and steam-distill the solution,collecting about 95mLof the distillate in a 100-mLvolumetric flask.Add water to volume,and mix.
Procedure— Transfer 20.0-mLportions of the Standard preparationand the Test preparationto separate 100-mLbeakers,and transfer 20.0mLof water to a third 100-mLbeaker to provide the blank.Treat each as follows.Add 5.0mLof 1Nhydrochloric acid,and cool in an ice bath.Add 2.0mLof 0.1Msodium nitrite dropwise,with stirring,allow to stand for 5minutes for the diazotization reaction to be complete,add quickly to 10.0mLof a cold solution of guaiacol (freshly prepared by dissolving 0.20g of guaiacol in 100mLof 1Nsodium hydroxide),mix,and allow to stand for 30minutes.Concomitantly determine the absorbances of the solutions at the wavelength of maximum absorbance at about 405nm,with a suitable spectrophotometer,using the blank to set the instrument:the absorbance of the solution obtained from the Test preparationdoes not exceed that of the solution obtained from the Standard preparation,corresponding to not more than 0.002%of volatile diazotizable substances,as p-toluidine.
Chloride á221ñ— A1.4-g portion shows no more chloride than corresponds to 0.4mLof 0.020Nhydrochloric acid (0.02%).
Sulfate á221ñ— A1.4-g portion shows no more sulfate than corresponds to 0.3mLof 0.020Nsulfuric acid (0.02%).
Assay— Transfer about 500mg of Aminobenzoate Potassium,accurately weighed,to a suitable vessel,add 25mLof water and 25mLof 3Nhydrochloric acid,mix,and cool in an ice bath.Titrate with 0.1Msodium nitrite VS,determining the endpoint potentiometrically,using a calomel-platinum electrode system.Each mLof 0.1Msodium nitrite is equivalent to 17.52mg of C7H6KNO2.
Auxiliary Information— Staff Liaison:Clydewyn M.Anthony,Ph.D.,Scientist
Expert Committee:(PA2)Pharmaceutical Analysis 2
USP28–NF23Page 120
Phone Number:1-301-816-8139