Standard preparation
Transfer about 12 mg of
USP Cefamandole Nafate RS, accurately weighed, to a 50-mL volumetric flask containing 4 mL of water. Immediately before use, add 30.0 mL of
pH 2.3 Buffer, dilute with water to volume, and mix.
Procedure
Transfer a portion of the
Assay preparation to a suitable polarographic cell. Deaerate by bubbling scrubbed nitrogen through the solution for 5 minutes, and redirect the nitrogen flow to the surface outlet. Insert the dropping mercury electrode of a suitable polarograph (see
Polarography 801) capable of measuring a current of 0.5 microampere or appropriate current to maintain on-scale response, using an average capillary, and a drop rate of 1 per second. Record the polarogram in the differential pulse mode from
0.3 volt to
1.05 volts, using a saturated calomel reference electrode and platinum wire counter electrode. Determine the peak height obtained, in microamperes, where the peak height is defined as the perpendicular distance from the extrapolated baseline to the highest point of the peak as compared to the full-scale current range. Similarly, determine the peak current of the
Standard preparation. Calculate the quantity, in µg, of C
18H
18N
6O
5S
2 in each mg of the Cefamandole Nafate taken by the formula:
P(WS / WU)(iU / iS),
in which
P is the potency, in µg of cefamandole per mg, of
USP Cefamandole Nafate RS;
WS and
WU are the quantities, in mg, of
USP Cefamandole Nafate RS and Cefamandole Nafate taken to prepare the
Standard preparation and the
Assay preparation, respectively; and
iU and
iS are the peak currents, in microamperes, from the
Assay preparation and the
Standard preparation, respectively.