Identification—
Dissolve about 1 g of the Capsule contents in 25 mL of water, add 5 mL of 3 N hydrochloric acid, and wash the precipitate with two 5-mL portions of cold water. Recrystallize from alcohol the precipitate so obtained, and dry at 110
for 1 hour: the
p-aminobenzoic acid so obtained melts between 186
and 189
.
Dissolution 
711
—
Medium:
water; 900 mL.
Apparatus 1:
100 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of C
7H
6KNO
2 dissolved by employing UV absorption at the wavelength of maximum absorbance at about 270 nm on filtered portions of the solution under test, suitably diluted with
Medium, in comparison with a Standard solution having a known concentration of
USP Aminobenzoate Potassium RS in the same
Medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of C7H6KNO2 is dissolved in 45 minutes.
Assay—
Assay preparation—
Remove as completely as possible, and combine, the contents of not fewer than 20 Capsules. Transfer an accurately weighed portion of the combined contents, equivalent to about 100 mg of aminobenzoate potassium, to a 200-mL volumetric flask, add 150 mL of water, shake by mechanical means for 30 minutes, dilute with water to volume, mix, and filter. Pipet 2 mL of the filtrate into a 200-mL volumetric flask, dilute with water to volume, and mix.
Procedure—
Concomitantly determine the absorbances of the
Standard preparation and the
Assay preparation at the wavelength of maximum absorbance at about 270 nm, with a suitable spectrophotometer, using water as the blank. Calculate the quantity, in mg, of aminobenzoate potassium (C
7H
6KNO
2) in the portion of Capsule contents taken by the formula:
20C(AU / AS),
in which
C is the concentration, in µg per mL, of
USP Aminobenzoate Potassium RS in the
Standard preparation; and
AU and
AS are the absorbances of the
Assay preparation and the
Standard preparation, respectively.
