Identification—
Prepare a solution containing about 5 mg of ampicillin per mL, using powder from Ampicillin Capsules, in a mixture of acetone and 0.1 N hydrochloric acid (4:1). Prepare a Standard solution of
USP Ampicillin RS to contain 5 mg per mL in the same solvent mixture. Apply separately 2 µL of each solution on a thin-layer chromatographic plate (see
Chromatography 
621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Place the plate in a suitable chromatographic chamber, and develop the chromatogram in a solvent system consisting of a mixture of acetone, water, toluene, and glacial acetic acid (650:100:100:25). When the solvent front has moved about three-fourths of the length of the plate, remove the plate from the chamber, mark the solvent front, and allow to air-dry. Locate the spots on the plate by spraying lightly with a solution of ninhydrin in alcohol containing 3 mg per mL, and dry at 90
for 15 minutes: the
RF value of the principal spot obtained from the solution under test corresponds to that obtained from the Standard solution.
Dissolution, Procedure for a Pooled Sample 711—
Medium:
water; 900 mL.
Apparatus 1:
100 rpm.
Time:
45 minutes.
Standard preparation—
Dissolve an accurately weighed quantity of
USP Ampicillin RS in water to obtain a solution having a known concentration of about
L/900 mg per mL,
L being the labeled amount, in mg, of ampicillin per Capsule.
Procedure—
Proceed as directed for
Procedure in the section
Antibiotics—Hydroxylamine Assay under
Automated Methods of Analysis 16, using a filtered portion of the solution under test as the
Assay preparation. Calculate the quantity, in mg, of C
16H
19N
3O
4S dissolved by the formula:
0.9CP(AU / AS).
Tolerances—
Not less than 75% (Q) of the labeled amount of C16H19N3O4S is dissolved in 45 minutes.
Assay—
Assay preparation—
Place not fewer than 5 Capsules in a high-speed glass blender jar containing an accurately measured volume of water, and blend for 4 ± 1 minutes. Dilute an accurately measured volume of this stock solution quantitatively and stepwise with water to obtain an Assay preparation containing about 1.25 mg of ampicillin per mL.
Procedure—
Proceed as directed for
Procedure under
Iodometric Assay—Antibiotics 425. Calculate the quantity, in mg, of ampicillin (C
16H
19N
3O
4S) in each Capsule taken by the formula:
(
T /
D)(
F / 2000)(
B 
I),
in which
T is the labeled quantity, in mg, of ampicillin in each Capsule; and
D is the concentration, in mg per mL, of ampicillin in the
Assay preparation on the basis of the labeled quantity in each Capsule and the extent of dilution.
