Chromatographic purity
Dissolve 125 mg in 10 mL of methanol to obtain the
Test solution. Dissolve
USP Tolmetin Sodium RS in methanol to obtain a
Standard solution having a concentration of 12.5 mg per mL. Dilute a portion of this
Standard solution quantitatively with methanol to obtain a
Diluted standard solution having a concentration of 62.5 µg per mL. Apply separate 20-µL portions of the three solutions on the starting line to a suitable thin-layer chromatographic plate (see
Chromatography 621) coated with 0.25-mm layer of chromatographic silica gel mixture. Develop the chromatogram in a solvent system consisting of a mixture of chloroform and glacial acetic acid (95:5) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber, mark the solvent front, air-dry, and view under short-wavelength UV light: the
RF value of the principal spot from the
Test solution corresponds to that from the
Standard solution. Any other spot obtained from the
Test solution does not exceed in size or intensity the principal spot obtained from the
Diluted standard solution (0.5%), and the sum of the total impurities based on a comparison of the intensities of all such other spots with the
Diluted standard solution does not exceed 2.0%.