Chromatographic purity—
pH 3.5 Buffer—
Dissolve 68.0 g of monobasic potassium phosphate in 1000 mL of water, and adjust with phosphoric acid to a pH of 3.5 ± 0.05.
Mobile phase—
Prepare a suitable filtered and degassed mixture of water, acetonitrile, and
pH 3.5 buffer (55:43:2). Make adjustments if necessary (see
System Suitability under
Chromatography 
621
).
System suitability solution—
Prepare a solution in
Mobile phase containing about 0.01 mg per mL of
USP Ketoprofen RS and 0.005 mg per mL of 3-benzoylbenzoic acid.
[NOTE—Protect this solution from light.
]
Standard solution—
Dissolve an accurately weighed quantity of
USP Ketoprofen RS quantitatively in
Mobile phase to obtain a solution having a known concentration of about 0.002 mg per mL.
[NOTE—Protect this solution from light.
]
Test solution—
Transfer about 100 mg of Ketoprofen, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix. [NOTE—Protect this solution from light.]
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 233-nm detector and a 4.6-mm × 15-cm column that contains 3-µm packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the relative retention times are about 0.8 for 3-benzoylbenzoic acid and 1.0 for ketoprofen; the resolution,
R, between 3-benzoylbenzoic acid and ketoprofen is not less than 4; the column efficiency, determined from the ketoprofen peak, is not less than 2250 theoretical plates; and the tailing factor for the ketoprofen peak is not more than 2.0. Chromatograph the
Standard solution, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 5%.
Procedure—
Separately inject equal volumes (about 20 µL) of the
Standard solution and the
Test solution into the chromatograph, run the chromatograph for seven times the retention time for ketoprofen, record the chromatograms, and measure the areas for the peaks. Calculate the percentage of each impurity by the same formula:
10,000(C / W)(ri / rS),
in which
C is the concentration, in mg per mL, of
USP Ketoprofen RS in the
Standard solution; W is the weight, in mg, of Ketoprofen taken to prepare the
Test solution; ri is the response of each individual peak, other than the main ketoprofen peak, obtained from the
Test solution; and
rS is the response of the main ketoprofen peak obtained from the
Standard solution: not more than 0.2% of any individual impurity is found, and the sum of all impurities found is not more than 1.0%.
;)
-methyl-, (±)-.
and 
1