A: Transfer a portion of powdered Tablets, equivalent to about 50 mg of baclofen, to a glass-stoppered 40-mL centrifuge tube. Add 10.0 mL of a mixture of dehydrated alcohol and glacial acetic acid (4:1), shake by mechanical means for 30 minutes, and centrifuge. Apply 20 µL of this solution and 20 µL of a Standard solution containing 5 mg of USP Baclofen RS per mL in a mixture of dehydrated alcohol and glacial acetic acid (4:1) to a thin-layer chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel. Place the plate in a chromatographic chamber (see Chromatography 621) containing a solvent system consisting of a mixture of butyl alcohol, glacial acetic acid, and water (4:1:1), and develop the chromatogram until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, and dry in a current of warm air. Spray with a detecting reagent consisting of 0.4 g of ninhydrin in 95 mL of butyl alcohol and 5 mL of dilute glacial acetic acid (1 in 10) until the plate is slightly wet. Place the plate in an oven maintained at 100 for 10 minutes: the RF value of the principal orange-red spot obtained from the solution from the Tablets corresponds to that obtained from the Standard solution.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

Medium: 0.01 N hydrochloric acid; 500 mL for Tablets containing 10 mg or less of drug and 1000 mL for Tablets containing more than 10 mg of drug.

Apparatus 2: 50 rpm.

Time: 30 minutes.

Mobile phase and Chromatographic system—Proceed as directed in the Assay.

Procedure— Inject an accurately measured volume (about 190 µL) of a filtered portion of the solution under test into the chromatograph by means of a microsyringe or a sampling valve, record the chromatogram, and measure the response for the major peak. Calculate the quantity of C10H12ClNO2 dissolved in comparison with a Standard solution having a known concentration of USP Baclofen RS in the same Medium and similarly chromatographed.

Tolerances— Not less than 75% (Q) of the labeled amount of C10H12ClNO2 is dissolved in 30 minutes.

Diluting solution , Mobile phase, and Chromatographic system—Proceed as directed in the Assay.

Standard preparation— Transfer about 10 mg of USP Baclofen Related Compound A RS, accurately weighed, to a 10-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix. Transfer 4.0 mL of this solution to a 25-mL volumetric flask, dilute with Diluting solution to volume, and mix.

Test preparation— Use the Assay preparation.

Procedure— [NOTE—Use peak areas where peak responses are indicated.] Separately inject equal volumes (about 10 µL) of the Standard preparation and the Test preparation into the chromatograph, and proceed as directed in the Procedure under Assay. Calculate the percentage of baclofen related compound A in the portion of Tablets taken by the formula: in which C is the concentration of USP Baclofen Related Compound A RS, in mg per mL, in the Standard preparation; W is the weight of baclofen in the Test preparation; and rU and rS are the peak responses due to baclofen related compound A in the chromatograms of the Test preparation and the Standard preparation, respectively. Not more than 4.0% is found.

(Official January 1, 2007)

Diluting solution— Transfer 75 mL of methanol and 10 mL of glacial acetic acid to a 250-mL volumetric flask. Dilute with water to volume, and mix.

Mobile phase— Prepare a filtered and degassed mixture of 0.3 N acetic acid, methanol, and 0.36 N sodium 1-pentanesulfonate (550:440:20). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Baclofen RS in Diluting solution to obtain a solution having a known concentration of about 4 mg per mL.

Assay preparation— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 40 mg of baclofen, to a 50-mL flask. Transfer 10.0 mL of Diluting solution to the flask, sonicate to disperse, and shake by mechanical means for 30 minutes. Centrifuge a portion of this solution for 5 minutes, and filter.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 265-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 0.6 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, and allow the Assay preparation to elute for not less than three times the retention time of baclofen. Record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C10H12ClNO2 in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Baclofen RS in the Standard preparation; and rU and rS are the baclofen peak responses obtained from the Assay preparation and the Standard preparation, respectively.