Mobile phase— Prepare a filtered and degassed mixture of methanol,water,and glacial acetic acid (55:44:1).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).Resolution may be increased by increasing the proportion of water in the Mobile phase.

Solvent mixture— Prepare a mixture of methanol and water (1:1).

Internal standard solution— Prepare a solution of naproxen in methanol containing about 0.3mg per mL.

Standard stock solution— Dissolve an accurately weighed quantity of USP Ketorolac Tromethamine RSquantitatively in methanol to obtain a solution having a known concentration of about 0.24mg per mL.[NOTE—Protect this solution from light.]

Standard preparation— Transfer 5.0mLof the Standard stock solutionand 5.0mLof the Internal standard solutionto a 50-mLvolumetric flask,dilute with Solvent mixtureto volume,and mix.[NOTE—Protect this solution from light.]

Assay preparation— Transfer an accurately measured volume of the Injection,equivalent to about 12mg of ketorolac tromethamine,to a 50-mLvolumetric flask,dilute with methanol to volume,and mix.Transfer 5.0mLof this stock solution and 5.0mLof Internal standard solutionto a second 50-mLvolumetric flask,dilute with Solvent mixtureto volume,and mix.[NOTE—Protect both the stock solution and the Assay preparation from light.]

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L1.The flow rate is about 1.2mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.7for ketorolac and 1.0for naproxen,the resolution,R,between the ketorolac peak and the naproxen peak is not less than 5.4,the column efficiency determined from the ketorolac peak is not less than 2700theoretical plates,the tailing factor is not more than 1.5,and the relative standard deviation for replicate injections is not more than 1.5%.

Procedure— Separately inject equal volumes (about 100µL)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 ketorolac tromethamine (C15H13NO3·C4H11NO3)in each mLof the Injection taken by the formula: in which Cis the concentration,in mg per mL,of USP Ketorolac Tromethamine RSin the Standard stock solution;Vis the volume,in mL,of Injection taken to prepare the Assay preparation;and RUand RSare the ratios of the ketorolac peak response to the naproxen peak response obtained from the Assay preparationand the Standard preparation,respectively.