A: Transfer a portion of the contents of the Capsules, equivalent to about 100 mg of dicyclomine hydrochloride, to a separator containing 10 mL of water and 1 mL of hydrochloric acid. Extract the aqueous acid solution with two 30-mL portions of chloroform, transfer the chloroform extracts to a second separator containing 20 mL of water and 1 mL of sodium hydroxide solution (1 in 10), and shake. Filter the chloroform layer through anhydrous sodium sulfate into a suitable container, and add 3 mL of a freshly prepared 1 in 20 solution of acetyl chloride in anhydrous methanol, prepared by cautiously adding acetyl chloride dropwise to anhydrous methanol with stirring. Evaporate under reduced pressure at room temperature until the residue has been thoroughly dried: the IR absorption spectrum of a potassium bromide dispersion of the dicyclomine hydrochloride so obtained exhibits maxima and minima at the same wavelengths as that of a similar preparation of USP Dicyclomine Hydrochloride RS.

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.

Apparatus 2: 50 rpm.

Time: 45 minutes.

Mobile phase— Prepare as directed in the Assay.

0.04 M Phosphate buffer, pH 7.5— Dissolve 2.72 g of monobasic potassium phosphate in 450 mL of water, adjust with 10% sodium hydroxide to a pH of 7.5 ± 0.1, dilute with water to 500 mL, and mix.

Buffer–acetonitrile mixture— Prepare a mixture of 0.04 M Phosphate buffer, pH 7.5 and acetonitrile (1:1).

Standard solution— Prepare a solution in Medium having a known concentration of about 20 µg per mL of USP Dicyclomine Hydrochloride RS. Transfer 25.0 mL of this solution to a suitable flask, add 25.0 mL of the Buffer–acetonitrile mixture, and mix.

Test solution— Pass a portion of the solution under test through a 0.7-µm glass microfiber filter. Transfer 5.0 mL of the filtrate to a suitable flask, add 5.0 mL of the Buffer–acetonitrile mixture, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm × 15-cm column containing 3.5-µm packing L7. The flow rate is about 1.0 mL per minute. Chromatograph the Standard solution, and record the responses as directed for Procedure: the tailing factor for the analyte peak is not more than 2.0, and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 250 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the amount, in mg, of C19H35NO2·HCl dissolved.

Tolerances— Not less than 75% (Q) of the labeled amount of C19H35NO2·HCl is dissolved in 45 minutes.

(Official January 1, 2007)

0.02 M Phosphate buffer, pH 7.5— Dissolve 2.72 g of monobasic potassium phosphate in 900 mL of water, adjust with 10% sodium hydroxide to a pH of 7.5 ± 0.1, dilute with water to 1000 mL, and mix.

Mobile phase— Prepare a mixture of acetonitrile and 0.02 M Phosphate buffer, pH 7.5 (70:30), filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluent— Prepare a mixture of acetonitrile and water (70:30).

Standard preparation— Dissolve an accurately weighed quantity of USP Dicyclomine Hydrochloride RS in Diluent to obtain a solution having a known concentration of about 0.4 mg per mL. [NOTE—This solution is stable for 2 days.]

Assay preparation— Remove, as completely as possible, the contents of not fewer than 20 Capsules, and mix the contents. Transfer an accurately weighed portion of the powder, equivalent to about 20 mg of dicyclomine hydrochloride, to a 50-mL volumetric flask. Add 2.0 mL of water, and sonicate for at least 2 minutes to disperse the sample. Add 35 mL of acetonitrile, sonicate for at least 5 minutes, and shake by mechanical means for at least 30 minutes. Add 10 mL of water, allow the preparation to equilibrate to room temperature, then dilute with water to volume, and mix. Centrifuge, for at least 5 minutes, a portion of this solution in a 15-mL glass centrifuge tube. Use the clear supernatant.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 215-nm detector and a 4.6-mm × 15-cm column containing 3-µm packing L7. The flow rate is about 1.0 mL per minute. Chromatograph the Standard preparation, and record the responses as directed for Procedure: the tailing factor for the analyte peak is not more than 1.5; and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 50 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 dicyclomine hydrochloride (C19H35NO2·HCl) in the portion of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Dicyclomine Hydrochloride RS in the Standard preparation; and rU and rS are the areas of the dicyclomine peak obtained from the Assay preparation and the Standard preparation, respectively.