Penicillin V content—
Transfer about 40 mg, accurately weighed, to a 100-mL volumetric flask, add methanol to volume, and mix. Concomitantly determine the absorbances of this solution and of a similarly prepared Standard solution prepared with about 30 mg of
USP Penicillin V Potassium RS at the wavelength of maximum absorbance at about 276 nm. Determine the percentage of penicillin V taken by the formula:
P(aU / aS),
in which
P is the percentage content of penicillin V in the
USP Penicillin V Potassium RS, and
aU and
aS are the absorptivities of the solution of the specimen and the Standard solution, respectively: between 62.3% and 72.5% is found.
Assay—
Assay preparations—
Dissolve a quantity of Penicillin V Benzathine in 1.0 N sodium hydroxide to obtain a solution containing 2000 Penicillin V Units per mL. Pipet 2 mL of this solution into a glass-stoppered, 125-mL conical flask, and use as the
Assay preparation for
Inactivation and titration. Dilute a quantity of Penicillin V Benzathine quantitatively with water to obtain a suspension containing 2000 Penicillin V Units per mL. Pipet 2 mL of this suspension into a glass-stoppered, 125-mL conical flask, and use as the
Assay preparation for the
Blank determination.
Procedure—
Proceed as directed for
Procedure under
Iodometric Assay—Antibiotics 
425
, except in the
Inactivation and titration of the specimen to omit the addition of 2.0 mL of 1.0 N sodium hydroxide. Calculate the potency, in Penicillin V Units per mg, in the Penicillin V Benzathine taken by the formula:
(
F)(
B 
I) / (2
D),
in which
D is the concentration, in mg per mL, of the
Assay preparation for
Inactivation and titration on the basis of the weight of Penicillin V Benzathine taken and the extent of dilution.
;)
,5
)]-, compd. with N,N¢-bis(phenylmethyl)-1,2-ethanediamine (2:1).