A: Transfer a quantity of Elixir, equivalent to about 1.25 mg of hyoscyamine sulfate, to a separator. Render alkaline with 6 N ammonium hydroxide, and extract with 50 mL of methylene chloride, filtering the extract into a beaker. Evaporate to dryness. Add 2 drops of nitric acid to the dry residue, and evaporate on a steam bath to dryness. Add a few drops of alcoholic potassium hydroxide TS: a violet color appears.

B: Transfer a quantity of Elixir, equivalent to about 2.5 mg of hyoscyamine sulfate, to a separator. Render acidic with 3 N sulfuric acid, and extract with methylene chloride. Discard this extract. Render the solution alkaline with 6 N ammonium hydroxide, and extract with methylene chloride, filtering the extract into a beaker. Evaporate to dryness. Dissolve the residue in a small amount of 0.1 N hydrochloric acid, and add gold chloride TS, with shaking, until a definite precipitate separates. Slowly heat until the precipitate dissolves, and allow the solution to cool: lustrous golden yellow scales are formed.

(Official January 1, 2007)

Diluent— Use 0.01 N hydrochloric acid.

Buffer solution— Transfer 13.6 g of monobasic potassium phosphate to a 2000-mL volumetric flask, dissolve in about 1800 mL of water, adjust with phosphoric acid to a pH of 3.0 ± 0.1, dilute with water to volume, mix, and filter.

Mobile phase— Prepare a degassed mixture containing Buffer solution and methanol (75:25).

Standard stock preparation— Dissolve an accurately weighed quantity of USP Hyoscyamine Sulfate RS in Diluent to obtain a solution having a concentration of about 0.16 mg of anhydrous hyoscyamine sulfate per mL. [NOTE—This solution may be stored in a refrigerator for 30 days.]

Standard preparation— Transfer 3.0 mL of the Standard stock preparation into a 100-mL volumetric flask, dilute with Diluent, to volume and mix. Calculate the concentration, C, in mg per mL, of anhydrous hyoscyamine sulfate in this solution.

Tropic acid solution— Dissolve an accurately weighed quantity of tropic acid in Diluent to obtain a solution having a concentration of about 4 µg of tropic acid per mL.

System suitability preparation— Transfer 3.0 mL of the Standard stock preparation into a 100-mL volumetric flask, add 4.0 mL of the Tropic acid solution, dilute with Diluent, to volume and mix.

Assay preparation— Transfer an accurately measured volume of Elixir, equivalent to about 0.25 mg of hyoscyamine sulfate, to a 50-mL volumetric flask, dilute with Diluent to volume, and mix. Pass an aliquot through a 0.45-µm filter, discarding the first 5 mL of the filtrate.

Chromatographic system— The liquid chromatograph is equipped with a 205-nm detector and a 4.6-mm × 15-cm column that contains 4-µm packing L11 and a 3-mm × 4-mm guard column that contains packing L11. The flow rate is about 1.0 mL per minute. The column temperature is maintained at 30. Chromatograph the System suitability preparation, and record the peak responses as directed for Procedure: the elution order is tropic acid peak, followed by hyoscyamine peak; the resolution, R, between tropic acid and hyoscyamine is not less than 1.5; the tailing factor for the hyoscyamine 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 50 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the area responses for the major peaks. Calculate the quantity, in mg, of hyoscyamine sulfate [(C17H23NO3)2·H2SO4·2H2O] in each mL of the Elixir taken by the formula: in which 1.053 is the ratio of the molecular weight of hydrated hyoscyamine sulfate to that of anhydrous hyoscyamine sulfate; C is as defined in the Standard preparation; V is the volume, in mL, of the Elixir taken; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.