A: Infrared Absorption 197K.

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.

Standard solution— Transfer about 5.0 g of acetone and 0.6 g of methylene chloride, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with N,N-dimethylacetamide to volume, and mix. Pipet 1 mL of this solution into a 100-mL volumetric flask, dissolve in and dilute with N,N-dimethylacetamide to volume, and mix.

Test solution— Transfer about 500 mg of Carprofen, accurately weighed, to a 5-mL volumetric flask, dissolve in and dilute with N,N-dimethylacetamide to volume, and mix.

Chromatographic system (see Chromatography 621)— The gas chromatograph is equipped with a flame-ionization detector and a 0.53-mm × 30-m capillary column coated with 3.0-µm G43 stationary phase. The carrier gas is nitrogen, flowing at a rate of about 4.9 mL per minute. The split flow ratio is about 10:1. Initially the column temperature is maintained at 80 for 4 minutes, then is increased at a rate of 30 per minute to a temperature of 190, and maintained at 190 for at least 3 minutes. The injection port temperature is maintained at 210, and the detector temperature is maintained at 220. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: acetone elutes before methylene chloride; the resolution, R, between them is not less than 1.5; and the relative standard deviation for replicate injections, determined from the peak responses of acetone, is not more than 10.0%.

Procedure— Separately inject equal volumes (about 1 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure all the peak responses. Calculate the percentage of each residual solvent in the portion of Carprofen taken by the formula: in which CS is the concentration, in µg per mL, of the individual residual solvent in the Standard solution; W is the weight, in mg, of Carprofen taken to prepare the Test solution; rU is the peak response of the individual residual solvent in the Test solution; and rS is the peak response of the individual residual solvent in the Standard solution: not more than 5000 ppm of acetone is found; and not more than 600 ppm of methylene chloride is found.

Mobile phase and Chromatographic system— Proceed as directed in the Assay.

Test solution— Use the Assay preparation.

Procedure— Inject about 10 µL of the Test solution into the chromatograph, record the chromatogram, and measure the responses for all the peaks. Calculate the percentage of each related compound in the portion of Carprofen taken by the formula: in which ri is the response of each individual peak other than the major peak of carprofen; and rs is the sum of the peak responses: not more than 0.5% of each individual known related compound is found (see the relative retention times of these compounds in the table below); not more than 0.1% of each individual unknown related compound is found; and not more than 1.0% of total related compounds is found.

Mobile phase— Prepare a mixture of acetonitrile, water, methanol, and glacial acetic acid (40:35:25:0.2).

Carprofen related compound A solution— [note—Use low-actinic glassware.] Prepare a solution of USP Carprofen Related Compound A RS, accurately weighed, in Mobile phase, containing about 16 µg per mL, sonicating if necessary.

Standard preparation— [note—Use low-actinic glassware.] Prepare a solution of USP Carprofen RS, accurately weighed, in Mobile phase, containing about 160 µg per mL, sonicating if necessary.

System suitability solution— [note—Use low-actinic glassware.] Transfer 10 mL of Carprofen related compound A solution and 10 mL of Standard preparation into a 100-mL volumetric flask. Dilute with Mobile phase to volume, and mix.

Assay preparation— [note—Use low-actinic glassware.] Dissolve an accurately weighed quantity of Carprofen in Mobile phase, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 160 µg per mL.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 239-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between carprofen and carprofen related compound A is not less than 2.0; the column efficiency for the carprofen peak is not less than 5000 theoretical plates; the tailing factor for the carprofen peak is not more than 2.0; and the relative standard deviation for replicate injections of carprofen is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for all the peaks. Calculate the percentage of C15H12ClNO2 in the portion of Carprofen taken by the formula: in which P is the purity, in µg per mg, of USP Carprofen RS; CS and CU are the concentrations, in µg per mL, of the Standard preparation and the Assay preparation, respectively; and RU and RS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.USP31