Assay—
Mobile phase—
Place 14 mL of triethylamine and 5.7 mL of glacial acetic acid in a 100-mL volumetric flask, dilute with water to volume, and mix. Prepare a suitable mixture of water, acetonitrile, 1 N acetic acid, and this solution (876:120:2.8:1.2). Filter through a membrane filter (1-µm or finer porosity), and degas.
Standard preparation—
Dissolve a suitable quantity of
USP Cefoperazone Dihydrate RS, accurately weighed, in
Mobile phase to obtain a solution having a known concentration of about 0.16 mg of cefoperazone (C
25H
27N
9O
8S
2) per mL.
Assay preparation—
Using a suitable quantity of Cefoperazone Sodium, accurately weighed, proceed as directed under Standard preparation.
Chromatographic system
(see
Chromatography 
621
)—The liquid chromatograph is equipped with a 254-nm detector and a 4.0-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed under
Procedure: the relative standard deviation for replicate injections is not more than 2.0%, and the tailing factor is not more than 1.5.
Procedure—
Separately inject equal volumes (about 10 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 cefoperazone per mg, of the Cefoperazone Sodium taken by the formula:
1000(C / M)(rU / rS),
in which
C is the concentration, in mg of cefoperazone (C
25H
27N
9O
8S
2) per mL, of the
Standard preparation;
M is the concentration, in mg per mL, of the
Assay preparation based on the weight of Cefoperazone Sodium taken and the extent of dilution; and
rU and
rS are the peak responses from the
Assay preparation and the
Standard preparation, respectively.
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