Assay—
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 C
19H
16ClNO
4 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.
;)
for 2 hours: it loses not more than 0.5% of its weight.