A: The IR absorption spectrum of a potassium bromide dispersion of it exhibits maxima only at the same wavelengths as that of a similar preparation of USP Ritodrine Hydrochloride RS.

B: The retention time of the ritodrine hydrochloride in the Assay preparation obtained in the Assay corresponds to that of the Standard preparation obtained in the Assay.

C: A solution (1 in 100) responds to the tests for Chloride 191.

Mobile phase and Chromatographic system— Prepare as directed in the Assay.

Test preparation— Prepare a solution containing about 1 mg of Ritodrine Hydrochloride in each mL of Mobile phase.

Diluted test preparation— Quantitatively dilute a suitable volume of the Test preparation with Mobile phase to obtain a solution having a known concentration of 0.01 mg per mL of ritodrine hydrochloride.

Procedure— Chromatograph the Test preparation and the Diluted test preparation, as directed in the Assay. The relative retention times are about 0.3 for tyramine, 0.65 for erythro-1-(4-ketocyclohexyl)-2-[(1-hydroxyphenethyl)amino]propanol-1, 0.85 for erythro-p-hydroxy-[1-(4-ketocyclohexylethyl)amino]ethyl benzyl alcohol, 1.0 for ritodrine, 1.15 for threo diastereomer of ritodrine, and 2.3 for p-hydroxy--(p-hydroxyphenethyl)amino]propiophenone. Determine the peak responses for ritodrine and for the related compounds from the chromatograms obtained from the Diluted test preparation and the Test preparation, respectively. Calculate the percentage of related compounds found: not more than 0.5% of any individual impurity and not more than 2.0% of total impurities is found.

(Official January 1, 2007)

Mobile phase— Dissolve 6.6 g of dibasic ammonium phosphate and 1.1 g of sodium 1-heptanesulfonate in 700 mL of water, and mix with 300 mL of methanol. Adjust by the addition of phosphoric acid to a pH of 3.0, mix, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Ritodrine Hydrochloride RS in Mobile phase to obtain a solution having a known concentration of about 0.2 mg per mL.

Assay preparation— Transfer about 200 mg of Ritodrine Hydrochloride, accurately weighed, to a 100-mL volumetric flask, dissolve in Mobile phase, dilute with Mobile phase to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.

System suitability preparation— Dissolve about 20 mg of Ritodrine Hydrochloride in about 50 mL of Mobile phase. Add 5.6 mL of sulfuric acid, dilute with Mobile phase to 100 mL, and mix. Heat a portion of this solution for about 2 hours at about 85, and then cool to room temperature. Cautiously mix 10.0 mL of the cooled solution with 8.0 mL of sodium hydroxide solution (1 in 10), and allow to cool. This solution contains ritodrine and its threo diastereomer.

Chromatographic system— The chromatograph is equipped with a 4.6-mm × 25-cm stainless steel column that contains packing L7 and an UV detector that monitors absorption at 214 nm. Chromatograph about 50 µL of the System suitability preparation: the resolution between ritodrine and its threo diastereomer is not less than 1.0. [NOTE—Chromatograms obtained as directed for this test, exhibit relative retention times of 1.0 for ritodrine and approximately 1.2 for the threo diastereomer.]

Procedure— Separately inject equal volumes (20 to 50 µL) of the Standard preparation and the Assay preparation into the chromatograph (see Chromatography 621) by means of a suitable sampling valve. Record the chromatograms and measure the peak responses. Calculate the quantity, in mg, of C17H21NO3·HCl in the portion of Ritodrine Hydrochloride taken by the formula: in which C is the concentration, in mg per mL, of USP Ritodrine Hydrochloride RS in the Standard preparation; and rU and rS are the peak responses for Ritodrine Hydrochloride obtained from the Assay preparation and the Standard preparation, respectively.