A: To one portion of the dry residue add 2 drops of nitric acid, evaporate on a steam bath to dryness, and add a few drops of alcoholic potassium hydroxide TS: a violet color is produced.

B: Dissolve the other portion of the residue in 1 mL of 0.1 N hydrochloric acid, and add gold chloride TS, dropwise 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.

C: A filtered solution of Tablets responds to the tests for Sulfate 191.

(Official January 1, 2007)

Diluent, Buffer solution, Mobile phase, Standard stock preparation, and Standard preparation— Proceed as directed in the Assay under Hyoscyamine Sulfate Injection.

Tropic acid solution— Dissolve an accurately weighed quantity of tropic acid in Diluent to obtain a solution having a concentration of about 3 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— Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed quantity of the powder, equivalent to about 0.125 mg of hyoscyamine sulfate, to a 25-mL volumetric flask. Add about 20 mL of the Diluent, and sonicate for 15 minutes with occasional swirling. Allow to cool to room temperature, 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 the tropic acid peak, followed by the 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 1.8; and the relative standard deviation for six 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 the portion of Tablets 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 under Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.