A: To a portion of finely powdered Tablets, equivalent to about 800 mg of meprobamate, add 5 mL of dehydrated alcohol, and heat just below the boiling temperature for about 5 minutes, with occasional swirling. Cool, filter into 15 mL of solvent hexane, and mix. With the aid of suction, filter the crystals that form, and dry at 60: the crystals of meprobamate so obtained melt between 103 and 107, but the range between beginning and end of melting does not exceed 2.

B: A portion of the crystals obtained in Identification test A responds to Identification test A under Meprobamate.

Medium: deaerated water; 900 mL.

Apparatus 1: 100 rpm.

Time: 30 minutes.

Procedure— Determine the amount of C9H18N2O4 dissolved using the method set forth for the Assay, making any necessary volumetric adjustments.

Tolerances— Not less than 75% (Q) of the labeled amount of C9H18N2O4 is dissolved in 30 minutes.

Mobile phase— Prepare a filtered and degassed mixture of water and acetonitrile (7:3), making adjustments if necessary (see System Suitability under Chromatography 621).

Phenacetin stock solution— Dissolve phenacetin in acetonitrile to obtain a solution having a concentration of about 125 µg per mL. Pipet 20 mL of this solution into a 100-mL volumetric flask, add 30 mL of acetonitrile, dilute with water to volume, and mix.

Standard preparation— Transfer about 50 mg of USP Meprobamate RS, accurately weighed, to a 10-mL volumetric flask, add 3 mL of acetonitrile, and shake to dissolve. Dilute with water to volume, and mix to obtain a solution having a known concentration of about 5 mg of USP Meprobamate RS per mL.

Resolution solution— Transfer 25 mg of meprobamate to a 5-mL volumetric flask, add 1 mL of acetonitrile, and shake to dissolve. Add 1 mL of Phenacetin stock solution, dilute with water to volume, and mix.

Assay preparation— Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 250 mg of meprobamate, to a 50-mL volumetric flask, add 15 mL of acetonitrile, and shake to dissolve. Dilute with water to volume, mix, and filter, discarding the first 10 mL of the filtrate.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 200-nm detector and a 3.9- to 4.6-mm × 25- to 30-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the resolution, R, between the meprobamate and the phenacetin peaks is not less than 2.0, and the area of the phenacetin peak is not less than 65.0% and not more than 100.0% of the meprobamate peak area. The relative retention times are about 0.7 for meprobamate and 1.0 for phenacetin. 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 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 C9H18N2O4 in the portion of Tablets taken by the formula: in which C is the concentration, in mg per mL, of USP Meprobamate RS in the Standard preparation, and rU and rS are the meprobamate peak responses obtained from the Assay preparation and the Standard preparation, respectively.