Chromatographic purity—
Using the chromatogram of the
Assay preparation obtained in the
Assay, calculate the percentage of each impurity by the formula:
100ri / (ris + rc),
in which
ri is the peak area response of a given impurity;
ris is the sum of all of the impurity peak area responses; and
rc is the peak area response for the main cefotaxime peak.
[NOTE—Disregard any impurity peak that is less than 0.1%.
] Not more than 1.0% of any individual impurity is found, and the sum of all impurities found is not more than 3.0%.
Assay—
0.05 M Phosphate Buffer—
Dissolve 7.1 g of anhydrous dibasic sodium phosphate in 1000 mL of water, and adjust with phosphoric acid to a pH of 6.25.
Solution A—
Prepare a mixture of 0.05 M Phosphate Buffer and methanol (86:14). Pass through a filter having a porosity of 0.5 µm or less, and degas before use.
Solution B—
Prepare a mixture of 0.05 M Phosphate Buffer and methanol (60:40). Pass through a filter having a porosity of 0.5 µm or less, and degas before use.
Standard preparation—
Transfer about 40 mg of
USP Cefotaxime Sodium RS, accurately weighed, to a 50-mL volumetric flask, add about 40 mL of
Solution A, swirl to dissolve, dilute with
Solution A to volume, and mix.
[NOTE—Use this solution promptly. It may be used within 24 hours if stored in the refrigerator.
]
Sensitivity solution—
Transfer 2.0 mL of
Standard preparation to a 100-mL volumetric flask, dilute with
Solution A to volume, and mix. Transfer 2.0 mL of this solution to a 20-mL volumetric flask, dilute with
Solution A to volume, and mix.
Resolution solution—
Mix 1 mL of Standard preparation, 7.0 mL of water, and 2.0 mL of methanol. Add 25 mg of sodium carbonate, mix, and allow to stand at room temperature for 10 minutes, with occasional swirling. Add 3 drops of glacial acetic acid and 1 mL of Standard preparation, and mix.
Assay preparation—
Transfer about 40 mg of Cefotaxime Sodium, accurately weighed, to a 50-mL volumetric flask, add
Solution A to dissolve it, dilute with
Solution A to volume, and mix.
[NOTE—Use this solution promptly. It may be used within 24 hours if stored in a refrigerator.
]
Chromatographic system
(see
Chromatography 
621
)—The liquid chromatograph is equipped with a 235-nm detector and a 3.9-mm × 15-cm column that contains 5-µm packing L1 and is maintained at a constant temperature of about 30
. The flow rate is about 1 mL per minute. The system is equilibrated with 100%
Solution A. Seven minutes after injection of the solution under test, the proportion of
Solution B is increased linearly from 0% to 20% at a rate of 10% per minute and is maintained at that composition for 7 minutes. The proportion of
Solution B is then increased linearly at a rate of 2.7% per minute until the proportion of
Solution B is 100%, and is held at that composition for 5 minutes, after which the proportion of
Solution A is increased linearly to 100% at a rate of 20% per minute. Chromatograph the
Resolution solution, and record the peak responses as directed under
Procedure: the retention times are about 3.5 minutes for desacetylcefotaxime and 14 minutes for cefotaxime, and the resolution,
R, between the two peaks is not less than 20. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the retention time for the main cefotaxime peak is between 12 and 15 minutes, the tailing factor is not more than 2, and the relative standard deviation for replicate injections is not more than 1.5%. Chromatograph the
Sensitivity solution, and record the peak responses as directed under
Procedure: the response of the cefotaxime peak is between 0.18% and 0.22% of the response of the cefotaxime peak in the chromatogram obtained from the
Standard preparation.
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 areas for the major peaks. Calculate the quantity, in µg per mg, of cefotaxime (C
16H
17N
5O
7S
2) in the portion of Cefotaxime Sodium taken by the formula:
50(CP / W)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Cefotaxime Sodium RS in the
Standard preparation;
P is the designated content, in µg per mg, of cefotaxime (C
16H
17N
5O
7S
2) in
USP Cefotaxime Sodium RS;
W is the weight, in mg, of Cefotaxime Sodium taken to prepare the
Assay preparation; and
rU and
rS are the cefotaxime peak area responses obtained from the
Assay preparation and the
Standard preparation, respectively.
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