Identification—
The retention times of the major peaks in the chromatogram of the
Assay preparation are the same as those of the
Standard preparation, all relative to the internal standard, as obtained in the
Assay.
Dissolution 
711
—
Medium:
simulated gastric fluid TS, prepared without pepsin; 900 mL.
Apparatus 1:
100 rpm.
Time:
30 minutes.
Procedure—
Determine the absorbances of filtered portions of the solution under test, suitably diluted with
Dissolution Medium, if necessary, and Standard solutions having known concentrations of
USP Chlordiazepoxide RS and
USP Amitriptyline Hydrochloride RS in the same
Medium, at wavelengths of 239 nm and 309 nm, using
Dissolution Medium as the blank. Calculate the percentage of chlordiazepoxide (C
16H
14ClN
3O) dissolved by the formula:
100(CD / L)(AU / AS),
in which
C is the concentration, in mg per mL, of
USP Chlordiazepoxide RS in the
Standard solution determined at the wavelength of 309 nm;
D is the dilution factor of the diluted solution under test;
L is the labeled amount, in mg, of chlordiazepoxide in each Tablet; and
AU and
AS are the absorbances of the solution under test and the chlordiazepoxide
Standard solution, respectively, at the wavelength of 309 nm.
Calculate the percentage of amitriptyline (C20H23N) dissolved by the formula:
100(277.40/313.86)(CD / L)(AX / AS),
in which 277.40 and 313.86 are the molecular weights of amitriptyline and amitriptyline hydrochloride, respectively;
C is the concentration, in mg per mL, of
USP Amitriptyline Hydrochloride RS in the amitriptyline Standard solution;
D is the dilution factor of the diluted solution under test;
L is the labeled amount, in mg, of amitriptyline in each Tablet;
AS is the absorbance of the amitriptyline
Standard solution at the wavelength of 239 nm; and
AX is defined by the formula:
AU239 – AU309 (C309AS239 / C239AS309),
in which
AU239 and
AU309 are the absorbances of the solution under test measured at 239 nm and 309 nm, respectively;
C309 and
C239 are the concentrations, in mg per mL, of
USP Chlordiazepoxide RS in the
Standard solution obtained at wavelengths of 309 and 239 nm, respectively; and
AS239 and
AS309 are the absorbances of the chlordiazepoxide
Standard solution determined at the wavelengths indicated in the subscripts.
[NOTE—All of the chlordiazepoxide measurements may be made with either a single
Standard solution or two separate Standard solutions.
]
Tolerances—
Not less than 85% (Q) of the labeled amount of chlordiazepoxide (C16H14ClN3O) and an amount of amitriptyline hydrochloride equivalent to not less than 85% (Q) of the labeled amount of amitriptyline (C20H23N) are dissolved in 30 minutes.
Related compounds—
Transfer an accurately weighed portion of finely powdered Tablets, equivalent to about 25 mg of chlordiazepoxide, to a 10-mL conical flask, add 2.5 mL of acetone, and shake. Allow any undissolved particles to settle, and apply 50 µL of the supernatant to a thin-layer chromatographic plate (see
Chromatography 621), coated with a 0.25-mm layer of chromatographic silica gel. Apply to the same plate 20 µL of an acetone solution containing 1 mg per mL of
USP Chlordiazepoxide Related Compound A RS and 10 µL of an acetone solution containing 50 µg per mL of
USP 2-Amino-5-chlorobenzophenone RS. Develop the chromatogram in a chromatographic chamber (not previously saturated with the developing solvent) in ethyl acetate until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and allow the solvent to evaporate. Locate the spots on the plate by lightly spraying with 2 N sulfuric acid, drying at 105
for 15 minutes, and then spraying in succession with sodium nitrite solution (1 in 1000), ammonium sulfamate solution (1 in 200), and N-(1-naphthyl)ethylenediamine dihydrochloride solution (1 in 1000): any spots from the test solution are not greater in size or intensity than the spots at the respective
RF values produced by the Standard solutions, corresponding to not more than 4.0% of chlordiazepoxide related compound A, and not more than 0.1% of 2-amino-5-chlorobenzophenone.
Assay—
[NOTE—Use low-actinic glassware in this procedure.
]
pH 2.5 Buffer—
Mix 10.5 mL of 0.20 N sodium hydroxide with 100 mL of a solution consisting of 0.04 M acetic acid, 0.04 M phosphoric acid, and 0.04 M boric acid (prepared by dissolving 2.402 g of glacial acetic acid, 4.612 g of phosphoric acid, and 2.473 g of boric acid in sufficient water to obtain 1000 mL of solution).
Solvent mixture—
Prepare a mixture consisting of pH 2.5 Buffer, tetrahydrofuran, and methanol (5:4:1).
Mobile phase—
Prepare a solution of 0.01 M sodium lauryl sulfate in Solvent mixture.
Assay preparation—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 50 mg of chlordiazepoxide and about 125 mg of amitriptyline, to a 50-mL volumetric flask, add Solvent mixture to volume, sonicate to disperse the mixture, and allow undissolved particles to settle. Transfer 10.0 mL of the resulting solution to a 100-mL volumetric flask, dilute with Solvent mixture to volume, and mix. Pass a portion of this solution through a filter having a 5-µm or finer porosity, and use the filtrate as the Assay preparation.
Chromatographic system (see Chromatography 621)—
The chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains 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 resolution,
R, 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, and record the chromatogram. Measure the peak responses at approximate retention times of 5 minutes for chlordiazepoxide and 7 minutes for amitriptyline hydrochloride. Calculate the quantity, in mg, of chlordiazepoxide (C
16H
14ClN
3O) in the portion of Tablets taken by the formula:
0.5[C(rU / rS)]Z,
and calculate the quantity, in mg, of amitriptyline (C
20H
23N) in the portion of Tablets taken by the formula:
(277.40/313.86)[(0.5C)(rU / rS)]Y ,
in which
Z denotes chlordiazepoxide;
Y denotes amitriptyline hydrochloride; 277.40 is the molecular weight of amitriptyline; 313.86 is the molecular weight of amitriptyline hydrochloride;
C is the concentration, in µg per mL, of USP Reference Standard in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
