Medium: pH 6.0 phosphate buffer (see Buffer Solutions in the section Reagents, Indicators, and Solutions); 900 mL.

Apparatus 2: 75 rpm.

Time: 60 minutes.

Standard preparation— Dissolve an accurately weighed quantity of USP Penicillin G Potassium RS in Dissolution Medium, and dilute quantitatively with the same solvent to obtain a solution having a known concentration of about 400 Penicillin G Units per mL.

Procedure— Filter the solution under test, dilute with Dissolution Medium, if necessary, and proceed as directed for Procedure in the section Antibiotics—Hydroxylamine Assay, under Automated Methods of Analysis 16. Calculate the number of Penicillin G Units in each mL of the solution taken by the formula: in which C is the concentration, in Penicillin G Units per mL, of the Standard preparation.

Tolerances— Not less than 70% (Q) of the labeled amount of Penicillin G Units is dissolved in 60 minutes.

Standard preparation— Prepare as directed for Standard preparation under Iodometric Assay—Antibiotics 425, using USP Penicillin G Potassium RS.

Assay preparation— Place not less than 5 Tablets in a high-speed glass blender jar containing an accurately measured volume of Buffer No. 1, and blend for 4 ± 1 minutes. Dilute an accurately measured volume of this stock solution quantitatively with Buffer No. 1 to obtain an Assay preparation containing about 2000 Penicillin G Units per mL. Pipet 2 mL of this solution into each of two glass-stoppered, 125-mL conical flasks.

Procedure— Proceed as directed for Procedure under Iodometric Assay—Antibiotics 425. Calculate the quantity, in Penicillin G Units in each Tablet taken by the formula: in which L is the labeled quantity, in Penicillin G Units, in each Tablet, and D is the concentration, in Units per mL, of Penicillin G in the Assay preparation on the basis of the labeled quantity in each Tablet and the extent of dilution.