Limit of phenolic compounds
To about 5 mg add 1 drop of 3 N hydrochloric acid, 1 mL of water, and 2 drops of ferric chloride TS
. Mix, add 2 drops of potassium ferricyanide TS
, and observe after 2 minutes: no blue-green color develops.
Prepare a filtered and degassed solution containing 0.007 M docusate sodium and 0.007 M ammonium nitrate in a mixture of acetonitrile and water (70:30), and adjust the solution with glacial acetic acid to a pH of 3.4. [NOTEDissolve the docusate sodium in the acetonitrile and water mixture before adding the ammonium nitrate.]
Dissolve an accurately weighed quantity of USP Dextromethorphan Hydrobromide RS
in water to obtain a stock solution having a known concentration of about 1 mg per mL. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase
to volume, and mix.
Transfer about 100 mg of Dextromethorphan Hydrobromide, accurately weighed, to a 100-mL volumetric flask, add water to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.
(see Chromatography 621
)The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation
, and record the peak responses as directed for Procedure:
the tailing factor for the major peak is not more than 2.5; and the relative standard deviation is not more than 2.0%.
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 C18
NO· HBr in the portion of Dextromethorphan Hydrobromide taken by the formula:
1000C(rU / rS),
in which C
is the concentration, in mg per mL, of USP Dextromethorphan Hydrobromide RS
in the Standard preparation;
are the peak responses obtained from the Assay preparation
and the Standard preparation