Loss on drying 
731
—
Dry about 100 mg, accurately weighed, in vacuum at a pressure not exceeding 5 mm of mercury at 25
for 4 hours: it loses not more than 8.0% of its weight.
Assay—
[NOTE—Prepare solutions of plicamycin in low-actinic glassware.
]
Mobile phase—
Prepare a suitable filtered and degassed mixture of 650 mL of 0.01 M phosphoric acid and 350 mL of acetonitrile.
Standard preparations—
Dissolve an accurately weighed quantity of
USP Plicamycin RS in
Mobile phase to obtain a solution having a concentration of 500 µg of plicamycin per mL. Dilute this solution with
Mobile phase to obtain solutions containing 50, 100, and 150 µg of plicamycin per mL.
Assay preparation—
Transfer about 5 mg of Plicamycin, accurately weighed, to a 50-mL volumetric flask. Dissolve in Mobile phase, dilute with Mobile phase to volume, and mix.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 278-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1.3 mL per minute. Chromatograph replicate injections of the
Standard preparation, and record the peak responses as directed for
Procedure: the relative standard deviation is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 10 µL) of the
Standard preparations and the
Assay preparation into the chromatograph by means of a suitable microsyringe or sampling valve, record the chromatograms, and measure the responses for the major peaks. The retention time is about 13 minutes for plicamycin. Plot the peak responses of the
Standard preparations versus concentration, in µg per mL, of plicamycin, and draw the straight line best fitting the three plotted points. From the graph so obtained, determine the concentration, in µg per mL, of plicamycin in the
Assay preparation. Calculate the potency, in µg of C
52H
76O
24 per mg, taken by the formula:
(50C / W),
in which
C is the concentration, in µg per mL, of plicamycin in the
Assay preparation, and
W is the weight, in mg, of Plicamycin taken.
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,3
(1R*,3R*,4S*)]]-6-[[2,6-Dideoxy-3-O-(2,6-dideoxy-