Identification—
The chromatogram of the
Assay preparation obtained as directed in the
Assay exhibits a major peak for oxacillin, the retention time of which corresponds to that exhibited in the chromatogram of the
Standard preparation obtained as directed in the
Assay.
Dissolution 
711
—
Medium:
water; 900 mL.
Apparatus 1:
100 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of oxacillin (C
19H
19N
3O
5S) by a suitable validated spectrophotometric analysis of a filtered portion of the solution under test, suitably diluted with
Dissolution Medium, if necessary, in comparison with a Standard solution having a known concentration of
USP Oxacillin Sodium RS in the same medium.
Tolerances—
Not less than 75% (Q) of the labeled amount of C19H19N3O5S is dissolved in 45 minutes.
Assay—
Mobile phase
,
Standard preparation, and
Chromatographic system—Proceed as directed in the
Assay under
Oxacillin Sodium.
Assay preparation—
Remove, as completely as possible, the contents of not less than 10 Capsules, and weigh. Mix, and transfer an accurately weighed portion of the powder, equivalent to about 100 mg of oxacillin (C19H19N3O5S), to a 200-mL volumetric flask, add water to volume, and mix for 10 minutes with the aid of a magnetic stirrer. Filter about 25 mL of the resulting solution, discarding the first 5 mL of the filtrate. Transfer 10.0 mL of the clear filtrate to a 50-mL volumetric flask, dilute with water to volume, and mix. [NOTE—Use this Assay preparation on the day prepared.]
Procedure—
Proceed as directed for
Procedure in the
Assay under
Oxacillin Sodium. Calculate the quantity, in mg, of oxacillin (C
19H
19N
3O
5S) in the portion of Capsule contents taken by the formula:
in which the terms are as defined therein.
