A: Mix an amount of the Capsule contents, equivalent to about 50 mg of dextroamphetamine sulfate, with about 10 mL of water for 30 minutes, and filter into a small flask. Cool the filtrate to about 15, add 3 mL of 1 N sodium hydroxide, then add 1 mL of a mixture of 1 volume of benzoyl chloride and 2 volumes of anhydrous ethyl ether, and shake for 2 minutes. Filter the precipitate, wash with about 15 mL of cold water, and recrystallize twice from diluted alcohol: the benzoyl derivative of dextroamphetamine so obtained, after being dried at 105 for 1 hour, melts between 154 and 160.

B: The retention time of the major peak in the chromatogram of the Assay preparation is the same as that of the Standard preparation obtained in the Assay.

Medium: water; 500 mL.

Apparatus 1: 100 rpm.

Time: 45 minutes.

Procedure— Determine the amount of (C9H13N)2·H2SO4 dissolved, employing the procedure set forth in the Assay, making any necessary modifications.

Tolerances— Not less than 75% (Q) of the labeled amount of (C9H13N)2·H2SO4 is dissolved in 45 minutes.

(Official January 1, 2007)

Mobile phase— Dissolve 1.1 g of sodium 1-heptanesulfonate in 525 mL of water. Add 25 mL of dilute glacial acetic acid (14 in 100) and 450 mL of methanol. Adjust dropwise, if necessary, with glacial acetic acid to a pH of 3.3 ± 0.1. Filter through a 0.5-µm membrane filter. The volume of methanol may be adjusted so that the retention time for dextroamphetamine is about 5 minutes.

Standard preparation— Dissolve an accurately weighed quantity of USP Dextroamphetamine Sulfate RS in 0.12 N phosphoric acid to obtain a solution having a known concentration of about 0.3 mg per mL.

Assay preparation— Remove, as completely as possible, the contents of not fewer than 20 Capsules, and weigh. Transfer an accurately weighed portion of the mixed powder, equivalent to about 15 mg of dextroamphetamine sulfate, to a 50-mL volumetric flask. Add 40 mL of 0.12 N phosphoric acid, and sonicate for 15 minutes. Dilute with 0.12 N phosphoric acid to volume, and mix. Filter through a 0.5-µm membrane filter, discarding the first 20 mL of the filtrate.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph three replicate injections of the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation 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 by means of a suitable automatic injector or sampling valve, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of (C9H13N)2·H2SO4 in the portion of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Dextroamphetamine Sulfate RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.