Sterility 71
Where the label states that Cloxacillin Sodium is sterile, it meets the requirements when tested as directed for
Direct Inoculation of the Culture Medium under
Test for Sterility of the Product to be Examined, except to use Fluid Thioglycollate Medium containing polysorbate 80 solution (1 in 200) and an amount of sterile penicillinase sufficient to inactivate the cloxacillin in each tube, to use SoybeanCasein Digest Medium containing polysorbate 80 solution (1 in 200) and an amount of sterile penicillinase sufficient to inactivate the cloxacillin in each tube, and to shake the tubes once daily.
Assay
Buffer
Prepare a 0.02 M solution of monobasic potassium phosphate in water, and adjust with 2 N sodium hydroxide to a pH of 6.8.
Mobile phase
Prepare a mixture of
Buffer and acetonitrile (80:20). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation
Prepare a solution of
USP Cloxacillin Sodium RS in
Buffer having a known concentration of about 0.55 mg per mL.
Assay preparation
Transfer about 110 mg of Cloxacillin Sodium, accurately weighed, to a 200-mL volumetric flask, dilute with Buffer to volume, and mix. Stir with the aid of a magnetic stirrer for 5 minutes to dissolve.
Chromatographic system (see Chromatography 621)
The liquid chromatograph is equipped with a 225-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the tailing factor is not more than 1.8; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure
Separately inject equal volumes (about 20 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in µg, of cloxacillin (C
19H
18ClN
3O
5S) in each mg of Cloxacillin Sodium taken by the formula:
200(CE / W)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Cloxacillin Sodium RS in the
Standard preparation; E is the cloxacillin (C
19H
18ClN
3O
5S) equivalent, in µg per mg, of
USP Cloxacillin Sodium RS;
W is the weight, in mg, of Cloxacillin Sodium taken to prepare the
Assay preparation; and
rU and
rS are the cloxacillin peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.