A: Apply 2µLof Injection and 2µLof a solution of USP Terbutaline Sulfate RSin sodium chloride solution (0.9in 100)containing 1mg per mLto a suitable thin-layer chromatographic plate (see Chromatography á621ñ)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 1in 50solution of 4-aminoantipyrine in methanol,allow to air-dry,and spray with a 2in 25solution of potassium ferricyanide in a solvent prepared by mixing ammonium hydroxide with water (4:1):the RFvalue 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 preparationcorresponds to that in the chromatogram of the Standard preparationas obtained in the Assay.

Mobile phase ,Standard preparation,and Chromatographic system—Prepare as directed in the Assayunder 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 1mg per mL.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of (C12H19NO3)2·H2SO4in each mLof the Injection taken by the formula: in which Lis the labeled quantity,in mg per mL,of terbutaline sulfate in the Injection,Cis the concentration,in mg per mL,of USP Terbutaline Sulfate RSin the Standard preparation,Dis 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 rUand rSare the terbutaline peak responses obtained from the Assay preparationand the Standard preparation,respectively.