(in'' doe meth' a sin).
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C19H16ClNO4 357.79

1H-Indole-3-acetic acid, 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-.
1-(p-Chlorobenzoyl)-5-methoxy-2-methylindole-3-acetic acid [53-86-1].
» Indomethacin contains not less than 98.0 percent and not more than 101.0 percent of C19H16ClNO4, calculated on the dried basis.
Packaging and storage— Preserve in well-closed, light-resistant containers.
USP Reference standards 11
USP Indomethacin RS Click to View Structure
B: Ultraviolet Absorption 197U
Solution: 25 µg per mL.
Medium: hydrochloric acid in methanol (1 in 120).
Absorptivities at 318 nm, calculated on the dried basis, do not differ by more than 3.0%.
C: Its X-ray diffraction pattern (see X-ray Diffraction 941) conforms to that of USP Indomethacin RS.
Loss on drying 731 Dry it at a pressure below 5 mm of mercury at 100 for 2 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.2%.
Mobile phase— Prepare a suitable solution of 0.01 M monobasic sodium phosphate and 0.01 M dibasic sodium phosphate in acetonitrile and water (approximately 1:1).
Standard preparation— Dissolve an accurately weighed quantity of USP Indomethacin RS in Mobile phase to obtain a solution having a known concentration of about 0.1 mg per mL.
Assay preparation— Weigh accurately about 100 mg of Indomethacin, and transfer to a 100-mL volumetric flask. Dissolve in and dilute with Mobile phase to volume, and mix. Pipet 10 mL of this solution into a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm × 30-cm column that contains 10-µm packing L1. The flow rate is about 1 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed under Procedure: the column efficiency determined from the analyte peak is not less than 500 theoretical plates, and the relative standard deviation for replicate injections is not more than 1.0%.
Procedure— Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C19H16ClNO4 in the portion of Indomethacin taken by the formula:
1000C(rU / rS)
in which C is the concentration, in mg per mL, of USP Indomethacin RS in the Standard preparation; and rU and rS are the peak responses obtained at equivalent retention times from the Assay preparation and the Standard preparation, respectively.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Clydewyn M. Anthony, Ph.D.
Senior Scientific Liaison
(SM22010) Monographs - Small Molecules 2
Reference Standards RS Technical Services
USP35–NF30 Page 3496