A: Infrared Absorption á197Mñ—Do not dry specimens.

B: Ultraviolet Absorption á197Uñ—

Solution: 10µg per mL.

Medium: hydrochloric acid in methanol (1in 1200).

C: Prepare a test solution of it in a mixture of chloroform and methanol (1:1)containing 1mg per mL.Similarly prepare a Standard solution,using USP Piroxicam RS.Separately apply 20-µLportions of the test solution and the Standard solution to a suitable thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel.Allow the spots to dry,and develop the chromatogram in a solvent system consisting of a mixture of toluene and glacial acetic acid (95:5)until the solvent front has moved about three-fourths of the length of the plate.Remove the plate from the developing chamber,and air-dry.Place the plate in the developing chamber,and develop as before.Remove the plate from the chamber,mark the solvent front,and air-dry.Locate the spots on the plate by viewing under short-wavelength UVlight:the RFvalue of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.

Solvent— Use dimethyl sulfoxide.

Buffer— Dissolve 7.72g of anhydrous citric acid in 400mLof water,and separately dissolve 5.35g of dibasic sodium phosphate in 100mLof water.Add the phosphate solution to the citric acid solution,dilute with water to make 1000mL,and mix.

Mobile phase— Prepare a suitable mixture of Bufferand methanol (55:45),and degas.

Standard preparation— Dissolve an accurately weighed quantity of USP Piroxicam RSin 0.01Nmethanolic hydrochloric acid to obtain a solution having a known concentration of about 0.25mg per mL.Transfer 10.0mLof this solution to a 50-mLvolumetric flask,add about 25mLof 0.01Nmethanolic hydrochloric acid and 10.0mLof water,dilute with 0.01Nmethanolic hydrochloric acid to volume,and mix.This solution contains about 0.05mg per mL.

Assay preparation— Transfer about 50mg of Piroxicam,accurately weighed,to a 100-mLvolumetric flask,dilute with 0.01Nmethanolic hydrochloric acid to volume,and mix.Transfer 10.0mLof this solution to a second 100-mLvolumetric flask,add about 50mLof 0.01Nmethanolic hydrochloric acid and 20.0mLof water,dilute with 0.01Nmethanolic hydrochloric acid to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—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 1.2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the column efficiency is not less than 500theoretical plates,the tailing factor is not more than 1.5,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25µL)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 C15H13N3O4Sin the portion of Piroxicam taken by the formula: in which Cis the concentration,in mg per mL,of USP Piroxicam RSin the Standard preparation,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.