Specific rotation 
781S
:
between +124
and +134
.
Test solution:
a known amount of specimen, equivalent to about 50 mg of cephalothin, per mL, in water.
Loss on drying 731—
Dry about 100 mg, accurately weighed, in a capillary-stoppered bottle in vacuum at a pressure not exceeding 5 mm of mercury at 60
for 3 hours: it loses not more than 1.5% of its weight.
Chromatographic purity—
Mobile phase
,
Resolution solution, and
Chromatographic system—Proceed as directed in the
Assay.
Standard solution—
Use the
Standard preparation, prepared as directed in the
Assay, transfer 1.0 mL to a 100-mL volumetric flask, dilute with
Mobile phase to volume, and mix.
Test solution—
Use the
Assay preparation prepared as directed in the
Assay.
Procedure—
Proceed as directed for the
Procedure in the
Assay, except to inject equal volumes (about 20 µL) of the
Standard solution and the
Test solution and to continue the chromatography of the
Test solution for at least 4 times the retention time of the main cephalothin peak. The area of any peak in the chromatogram obtained from the
Test solution, except the main peak, is not greater than the area of the main peak in the chromatogram obtained from the
Standard solution (1.0%), and the sum of the areas of any such peaks is not greater than 3 times the area of the main peak in the chromatogram obtained from the
Standard solution (3.0%).
[NOTE—Any peak in the chromatogram obtained from the
Test solution with an area less than one-tenth that of the main peak in the chromatogram obtained from the
Standard solution is disregarded.
]
Assay—
Mobile phase—
Dissolve 17 g of sodium acetate in 790 mL of water, add 0.6 mL of glacial acetic acid, and if necessary adjust with 0.1 N sodium hydroxide or glacial acetic acid to a pH of 5.9 ± 0.1. Add 150 mL of acetonitrile and 70 mL of alcohol, and mix. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Cephalothin Sodium RS quantitatively in
Mobile phase to obtain a solution having a known concentration of about 1 mg per mL.
Resolution solution—
Heat a 5-mL portion of the
Standard preparation in a water bath at 90
for 10 minutes. Cool the solution, and immediately inject a portion of it into the chromatograph as directed under
Chromatographic system.
Assay preparation—
Transfer about 25 mg of Cephalothin Sodium, accurately weighed, to a 25-mL volumetric flask, add about 15 mL of Mobile phase, swirl to dissolve, dilute with Mobile phase to volume, and mix.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains 5 µm packing L1 and is maintained at a constant temperature of about 40
. The flow rate is about 1 mL per minute. Chromatograph the
Resolution solution, and record the peak responses as directed under
Procedure: the resolution between the two principal peaks is not less than 9.0. Chromatograph the
Standard preparation, and record the peak responses as directed under
Procedure: the tailing factor is not more than 1.8, and the relative standard deviation for replicate injections is not more than 1.0%.
Procedure—
[NOTE—Use peak areas where peak responses are indicated.
] 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 cephalothin (C
16H
16N
2O
6S
2) in each mg of Cephalothin Sodium taken by the formula:
25(CP / W)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Cephalothin Sodium RS in the
Standard preparation;
P is the assigned potency, in µg of cephalothin per mg, of
USP Cephalothin Sodium RS;
W is the quantity, in mg, of Cephalothin Sodium taken to prepare the
Assay preparation; and
rU and
rS are the cephalothin peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
