Chloride 
221
—
To 1 g of the substance under test, add 30 to 40 mL of water, and warm gently, if necessary, until no more dissolves. Mix well, and pass through a filter paper that gives a negative test for chloride. Add I mL of nitric acid and 1 mL of
silver nitrate TS. Dilute with water to 50 mL. Mix well, and allow to stand for 5 minutes protected from direct sunlight: any turbidity formed is not greater than that produced in a similarly treated control solution containing 0.3 mL of 0.020 N hydrochloric acid (0.02%).
Limit of ondansetron related compound D—
Phosphate buffer—
Dissolve about 2.72 g of monobasic potassium phosphate in 900 mL of water. Adjust with 1 N sodium hydroxide or 0.5 N sodium hydroxide to a pH of 5.4, dilute to 1000 mL, and mix.
Mobile phase—
Prepare a filtered and degassed mixture of
Phosphate buffer and acetonitrile (80:20). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard solution—
Dissolve an amount of
USP Ondansetron Related Compound D RS in
Mobile phase, and dilute stepwise with
Mobile phase, to obtain a solution having a known concentration of about 0.4 µg per mL.
Test solution—
Transfer about 50 mg of Ondansetron, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 328-nm detector and a 4.6-mm × 25-cm column that contains packing L10. The column temperature is maintained at 30
. The flow rate is about 1.5 mL per minute. Chromatograph the
Resolution solution, and record the peak responses as directed for
Procedure: the relative retention times are about 0.8 for ondansetron related compound C and 1.0 for ondansetron related compound D; and the resolution,
R, between ondansetron related compound C and ondansetron related compound D is not less than 1.5. Chromatograph the
Standard solution, and record the peak responses as directed for
Procedure: the column efficiency is not less than 8000 theoretical plates; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 20 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of ondansetron related compound D in the ondansetron taken by the formula:
10(C/W)(rU / rS),
in which
C is the concentration, in µg per mL, of
USP Ondansetron Related Compound D RS in the
Standard solution; W is the weight, in mg, of ondansetron taken to prepare the
Test solution; and
rU and
rS are the peak responses of ondansetron related compound D obtained from the
Test solution and the
Standard solution, respectively: not more than 0.10% is found.
Related compounds—
Phosphate buffer, Mobile phase, Resolution solution, Standard preparation, and Chromatographic system—
Prepare as directed in the Assay.
Test solution—
Use the Assay preparation prepared as directed in the Assay.
Procedure—
Inject a volume (about 10 µL) of the
Test solution into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each impurity in the portion of Ondansetron taken by the formula:
100(ri / rs),
in which
ri is the peak area for each impurity; and
rs is the sum of the areas of all the peaks: not more than 0.1% of any individual impurity is found; and not more than 0.5% of total impurities is found, including ondansetron related compound D.
[Note—Disregard the peak corresponding to ondansetron related compound D at a relative retention time of about 0.4.
]
Assay—
Phosphate buffer—
Dissolve about 2.72 g of monobasic potassium phosphate in 900 mL of water. Adjust with 1 N sodium hydroxide or 0.5 N sodium hydroxide to a pH of 5.4, dilute to 1000 mL, and mix.
Mobile phase—
Prepare a filtered and degassed mixture of
Phosphate buffer and acetonitrile (52:48). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Resolution solution—
Prepare a solution of USP Ondansetron RS and
USP Ondansetron Related Compound A RS in
Mobile phase having a known concentration of about 0.09 mg per mL and 0.05 mg per mL, respectively.
Standard preparation—
Dissolve an accurately weighed quantity of USP Ondansetron RS in Mobile phase, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.090 mg per mL.
Assay preparation—
Transfer about 45 mg of Ondansetron, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix. Pipet 5.0 mL of this solution into a 50-mL volumetric flask. Dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 216-nm detector and a 4.6-mm 25-cm column that contains packing L10. The flow rate is about 1.5 mL per minute. The column temperature is maintained at 30
. Chromatograph the
Resolution solution, and record the peak responses as directed for
Procedure: the relative retention times are about 1.1 for ondansetron related compound A and 1.0 for ondansetron; and the resolution,
R, between ondansetron related compound A and ondansetron is not less than 1.5. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 1.5%.
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 responses for the ondansetron peaks. Calculate the quantity, in mg, of C
18H
19N
3O in the portion of Ondansetron taken by the formula:
500C(rU / rS),
in which
C is the concentration, in mg per mL, of USP Ondansetron RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
