Protect Metolazone solutions from light.
Standard preparations
Dissolve an accurately weighed quantity of
USP Metolazone RS in tetrahydrofuran and mix to obtain
Standard preparation A having a known concentration of 0.50 mg per mL. Dilute a portion of
Standard preparation A quantitatively with tetrahydrofuran to obtain
Standard preparation B having a known concentration of 0.25 mg per mL.
Procedure
Separately apply 10 µL of the
Test preparation and each of the two
Standard preparations to a suitable thin-layer chromatographic plate (see
Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture. Allow the spots to dry, and develop the chromatogram in a solvent system consisting of a mixture of chloroform, ethyl acetate, and formic acid (55:40:5) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, air-dry, examine the plate under short-wavelength UV light, and compare the intensities of any secondary spots observed in the chromatogram of the
Test preparation with those of the principal spots in the chromatograms of the
Standard preparations: no secondary spot from the chromatogram of the
Test preparation is larger or more intense than the principal spot obtained from
Standard preparation B (0.5%) and the sum of the intensities of the secondary spots obtained from the
Test preparation corresponds to not more than 1.0%.