Dissolution 
711
—
pH 4.0 buffer—
Transfer 10.94 g of anhydrous dibasic sodium phosphate and 12.92 g of citric acid monohydrate to a 1-liter volumetric flask, dissolve in water, dilute with water to volume, and mix.
Medium:
pH 4.0 buffer; 900 mL.
Apparatus 2:
50 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of nafcillin (C
21H
22N
2O
5S) dissolved from UV absorbances, at the wavelength of maximum absorbance at about 280 nm of filtered portions of the solution under test, suitably diluted with
Medium, if necessary, in comparison with a Standard solution having a known concentration of
USP Nafcillin Sodium RS in the same medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of nafcillin (C21H22N2O5S) is dissolved in 45 minutes.
Assay—
Proceed as directed under
Antibiotics—Microbial Assays 81, using not less than 5 Tablets blended for 4 ± 1 minutes in a high-speed glass blender jar containing an accurately measured volume of
Buffer No. 1. Dilute an accurately measured volume of this stock solution quantitatively with
Buffer No. 1 to obtain a
Test Dilution having a concentration assumed to be equal to the median dose level of the Standard.
