Loss on drying
(see
Thermal Analysis 
891
)—
[NOTE—In this procedure, perform weighings rapidly with minimum exposure of the substances to air.
] Determine the percentage of volatile substances by thermogravimetric analysis on an appropriately calibrated instrument, using about 10 mg of Vinblastine Sulfate, accurately weighed. Heat the specimen at the rate of 5
per minute between ambient temperature and 200
in an atmosphere of nitrogen at a flow rate of 40 mL per minute. From the thermogram, determine the accumulated loss in weight between ambient temperature and a point on the plateau before decomposition is indicated (at about 160
): it loses not more than 15.0% of its weight.
Related compounds—
Mobile phase
,
System suitability preparation, and
Chromatographic system—Prepare as directed in the
Assay.
High load test preparation—
Prepare as directed for
Assay preparation in the
Assay.
Low load test preparation—
Pipet 1 mL of High load test preparation into a 25-mL volumetric flask, dilute with water to volume, and mix.
Procedure—
Separately inject 200 µL of the
Low load test preparation and of the
High load test preparation into the chromatograph, and record the chromatograms. Measure the peak responses,
ri, of any related substances appearing after the solvent peak in the chromatogram of the
High load test preparation. Calculate the total percentage of responses due to related substances taken by the formula:
100rt / (rt + 25rv),
in which
rt is the sum of the
ri responses; and
rv is the vinblastine peak response in the chromatogram of the
Low load test preparation. Not more than 3.0% is found. Calculate the percentage response of each related substance taken by the formula:
100ri / (rt + 25rv).
Not more than 1.0% of response due to any individual related substance is found.
Assay—
Mobile phase—
Mix 14 mL of diethylamine with 986 mL of water, and adjust with phosphoric acid to a pH of 7.5 (Solution A). Mix 200 mL of acetonitrile with 800 mL of methanol (Solution B). Mix 380 mL of Solution A with 620 mL of Solution B, pass through a 0.5-µm filter, and degas under vacuum. The ratio of Solutions A and B may be varied to meet system suitability requirements and to provide a suitable elution time for vinblastine sulfate.
Standard preparation—
Dissolve an accurately weighed quantity of
USP Vinblastine Sulfate RS in water to obtain a solution having a known concentration of about 0.4 mg per mL.
Assay preparation—
Transfer about 4 mg of Vinblastine Sulfate, accurately weighed, to a 10-mL volumetric flask, dissolve in and dilute with water to volume, and mix.
System suitability preparation—
Dissolve an amount of
USP Vincristine Sulfate RS in a portion of
Standard preparation to obtain a solution having concentrations of about 0.4 mg of each Reference Standard per mL.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 262-nm detector, a pre-column packed with porous silica gel installed between the pump and the injector, and a 4.6-mm × 15-cm analytical column that contains packing L1. The
Mobile phase is maintained at a pressure and flow rate (about 2 mL per minute) capable of producing the required resolution and a suitable elution time. 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%. Similarly chromatograph 20 µL of the
System suitability preparation, and record the peak responses: the resolution,
R, between the vincristine and vinblastine is not less than 4.0.
[NOTE—For a particular column, the resolution may be increased by increasing the proportion of
Solution A in the
Mobile phase.
]
Procedure—
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 mg, of C
46H
58N
4O
9.H
2SO
4 in the portion of Vinblastine Sulfate taken by the formula:
10C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Vinblastine Sulfate RS (corrected for loss in weight) in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
