A: Infrared Absorption 197K.

B: Ultraviolet Absorption 197U—

Solution: 5 µg per mL.

Medium: 0.001 N sodium hydroxide.

Standard preparation— Dissolve 10 mg of p-toluidine in 5 mL of methanol in a 100-mL volumetric flask, dilute water to volume, and mix. Transfer 1 mL to a 100-mL volumetric flask, dilute with water to volume, and mix.

Test preparation— Transfer 5.0 g of Aminobenzoic Acid to a suitable flask, and add a volume of 1.25 N sodium hydroxide that is just sufficient to dissolve the test specimen and to render the solution just alkaline to phenolphthalein TS. Dilute with water to 50 mL, and steam-distill the solution, collecting about 95 mL of the distillate in a 100-mL volumetric flask. Add water to volume, and mix.

Procedure— Transfer 20.0-mL portions of the Standard preparation and the Test preparation to separate 100-mL beakers, and transfer 20.0 mL of water to a third 100-mL beaker to provide the blank. Treat each as follows. Add 5.0 mL of 1 N hydrochloric acid, and cool in an ice bath. Add 2.0 mL of 0.1 M sodium nitrite dropwise, with stirring, allow to stand for 5 minutes in order for the diazotization reaction to be complete, add quickly to 10.0 mL of a cold solution of guaiacol (freshly prepared by dissolving 0.20 g of guaiacol in 100 mL of 1 N sodium hydroxide), mix, and allow to stand for 30 minutes. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 450 nm, using the blank to set the instrument: the absorbance of the solution obtained from the Test preparation does 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.

Test solution: alcohol.

Standard solution: alcohol.

Eluant: a mixture of toluene, ethyl acetate, and alcohol (60:20:20), in a nonequilibrated chamber.

Visualization: 1.

(Official January 1, 2007)