Identification—
A:
Thin-Layer Chromatographic Identification Test 
201
—
Test solution—
Transfer a volume of Oral Solution, equivalent to about 10 mg of codeine phosphate, to a separator, and add 5 mL of water, 5 mL of methylene chloride, and 1 mL of ammonium hydroxide. Shake for 1 minute, allow the layers to separate, and use the clear, lower layer.
Developing solvent system:
a mixture of alcohol and ammonium hydroxide (49:1).
B:
The retention times of the major peaks in the chromatogram of the Assay preparation correspond to those in the chromatogram of the Standard preparation, as obtained in the Assay.
Microbial limits 61—
It meets the requirements of the tests for absence of
Salmonella species,
Escherichia coli, Staphylococcus aureus, and
Pseudomonas aeruginosa. The total aerobic microbial count does not exceed 100 cfu per mL, and the total combined molds and yeasts count does not exceed 50 cfu per mL.
Assay—
Diluent—
Prepare a mixture of methanol and water (80:20).
Mobile phase—
Prepare a filtered and degassed mixture of methanol, water, 0.1 N ammonium hydroxide solution, and 0.1 N ammonium nitrate solution (27:3:2:1). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Assay preparation—
Using a pipet calibrated “to contain”, transfer an accurately measured volume of Oral Solution, equivalent to about 10 mg of bromodiphenhydramine hydrochloride and 8 mg of codeine phosphate, to a 100-mL volumetric flask, dissolve in and dilute with Diluent to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30.0-cm column that contains packing L3. The flow rate is about 1.0 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative retention times are about 1.0 for bromodiphenhydramine and 1.4 for codeine; the resolution,
R, between bromodiphenhydramine and codeine is not less than 2.0; 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 preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the peak responses for bromodiphenhydramine and codeine. Calculate the quantity, in mg, of bromodiphenhydramine hydrochloride (C
17H
20BrNO·HCl) in each mL of the Oral Solution taken by the formula:
100(C/V)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Bromodiphenhydramine Hydrochloride RS in the
Standard preparation; V is the volume, in mL, of Oral Solution taken to prepare the
Assay preparation; and
rU and
rS are the bromodiphenhydramine peak responses obtained from the
Assay preparation and the
Standard preparation, respectively. Calculate the quantity, in mg, of codeine phosphate hemihydrate (C
18H
21NO
3·H
3PO
4·½H
2O) in each mL of the Oral Solution taken by the formula:
(406.37/397.36)(100C/V)(rU / rS),
in which 406.37 and 397.36 are the molecular weights of codeine phosphate hemihydrate and anhydrous codeine phosphate, respectively;
C is the concentration, in mg per mL, of
USP Codeine Phosphate RS in the
Standard preparation; V is the volume, in mL, of Oral Solution taken to prepare the
Assay preparation; and
rU and
rS are the codeine peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
