A: Apply 2 µL of Injection and 2 µL of a solution of USP Terbutaline Sulfate RS in sodium chloride solution (0.9 in 100) containing 1 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 isopropyl alcohol, cyclohexane, and formic acid (13:5:1) 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 with a current of air. Spray the plate with a 1 in 50 solution of 4-aminoantipyrine in methanol, allow to air-dry, and spray with a 2 in 25 solution of potassium ferricyanide in a solvent prepared by mixing ammonium hydroxide with water (4:1): the RF value of the principal spot obtained from the Injection corresponds to that obtained from the Standard solution.

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

Mobile phase , Standard preparation, and Chromatographic system—Prepare as directed in the Assay under Terbutaline Sulfate.

Assay preparation— Use Injection. If necessary, quantitatively dilute an accurately measured volume of Injection with water to obtain a solution having a concentration of about 1 mg per mL.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of (C12H19NO3)2·H2SO4 in each mL of the Injection taken by the formula: in which L is the labeled quantity, in mg per mL, of terbutaline sulfate in the Injection, C is the concentration, in mg per mL, of USP Terbutaline Sulfate RS in the Standard preparation, D is the concentration, in mg per mL, of terbutaline sulfate in the Assay preparation, based upon the labeled quantity, in mg per mL, of terbutaline sulfate in the Injection and the extent of dilution, and rU and rS are the terbutaline peak responses obtained from the Assay preparation and the Standard preparation, respectively.