á223ñDIMETHYLANILINE

Internal Standard Solution— Unless otherwise specified in the individual monograph,prepare a solution of naphthalene in cyclohexane containing about 50µg per mL.

Standard Preparation— Unless otherwise specified in the individual monograph,transfer 50.0mg of N,N-dimethylaniline to a 50-mLvolumetric flask,add 25mLof 1Nhydrochloric acid,swirl to dissolve,dilute with water to volume,and mix.Transfer 5.0mLof the resulting solution to a 250-mLvolumetric flask,dilute with water to volume,and mix.To a suitable centrifuge tube add 1.0mLof this solution,5.0mLof 1Nsodium hydroxide,and 1.0mLof Internal Standard Solution,shake vigorously for 1minute,and centrifuge.Use the clear supernatant as the Standard Preparation.

Test Preparation— Unless otherwise specified in the individual monograph,transfer 1.0g of the substance to be tested to a suitable centrifuge tube,add 5mLof 1Nsodium hydroxide,swirl to dissolve the specimen,add 1.0mLof Internal Standard Solution,shake vigorously for 1minute,and centrifuge.Use the clear supernatant as the Test Preparation.

Chromatographic System (see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 2-mm ×2-m column packed with 3%liquid phase G3on silanized packing S1Aand is maintained at 120.Nitrogen is used as the carrier gas,flowing at the rate of about 30mLper minute.

Procedure— Inject equal volumes (within the range of 2µLto 20µL)of theStandard Preparationand the Test Preparationinto the chromatograph,record the chromatograms,and measure the areas for the major peaks.The ratio of the response of any dimethylaniline peak to the response of the naphthalene peak obtained from the Test Preparationis not greater than that obtained from the Standard Preparation(0.002%).