A: Prepare 3 mL of a solution in chloroform having a concentration of about 6 mg per mL, and reserve a 1-mL portion for Identification test B. In a well-ventilated hood, apply 2 mL of this solution dropwise to a salt plate while continuously evaporating the solvent with the aid of an IR heat lamp and a current of dry air. Heat the residue at 105 for 15 minutes: the IR absorption spectrum of the residue on the single salt plate exhibits maxima only at the same wavelengths as that of a similar preparation of USP Propantheline Bromide RS, treated in the same manner.

B: Apply 5 µL of the chloroform solution retained from Identification test A and 5 µL of a Standard solution of USP Propantheline Bromide RS in chloroform containing 6 mg per mL to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel. Develop the chromatogram in a solvent system consisting of a mixture of 1 N hydrochloric acid and acetone (1:1) 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 dry at 105 for 5 minutes. Spray the plate with potassium-bismuth iodide TS, and heat at 105 for 5 minutes: the RF value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

C: To 5 mL of a solution (1 in 100) add 2 mL of 2 N nitric acid: this solution responds to the tests for Bromide 191, except that in the test that liberates bromine, the chloroform layer may be yellow.

pH 3.5 buffer solution— Dissolve 17.3 g of sodium dodecyl sulfate in 1000 mL of water containing 10 mL of phosphoric acid in a 2000-mL volumetric flask. Add 250 mL of 0.5 M sodium hydroxide and, while stirring, adjust with 0.5 M sodium hydroxide or dilute phosphoric acid (1 in 10) to a pH of 3.5 ± 0.05, dilute with water to volume, and mix.

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and pH 3.5 buffer solution (55:45). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard solution— Dissolve accurately weighed quantities of USP Propantheline Bromide Related Compound A RS, USP Xanthanoic Acid RS, and USP Xanthone RS in Mobile phase, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 6.0 µg of propantheline bromide related compound A per mL, and about 1.5 µg each of xanthanoic acid and xanthone per mL.

Test solution— Transfer about 60 mg of Propantheline Bromide, accurately weighed, to a 200-mL volumetric flask, dissolve in Mobile phase, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L7. The flow rate is about 2.0 mL per minute. Chromatograph the Standard solution, and record peak responses as directed for Procedure: the resolution, R, between the least resolved peaks is not less than 1.2; and the relative standard deviation for replicate injections of the Standard solution is not more than 6.0% for each component.

Procedure— Separately inject equal volumes (about 50 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms for a total time of not less than 1.5 times the retention time of the propantheline bromide peak, and measure the response for each peak, except the peaks at or before the void volume. Calculate the percentage of xanthanoic acid, xanthone, and propantheline bromide related compound A greater than or equal to 0.1% in the portion of Propantheline Bromide taken by the formula: in which C is the concentration, in µg, of xanthanoic acid, xanthone, or propantheline bromide related compound A per mL of the Standard solution; W is the weight, in mg, of Propantheline Bromide taken; and rU and rS are the related compound peak responses obtained from the Test solution and the Standard solution, respectively: not more than 2.0% of propantheline bromide related compound A and 0.5% each of xanthone and xanthanoic acid is found. Calculate the percentage of all unknown impurities greater than or equal to 0.1% by the formula: in which ri is the response of the unknown impurity peak; and rt is the sum of the responses of all the measured peaks observed in the chromatogram: the sum total of all known and unknown impurities is not more than 3.0%.