Identification—
Shake a portion of Capsule contents, equivalent to about 100 mg of gemfibrozil, with 10 mL of 0.1 N sodium hydroxide. Filter the mixture into a 50-mL centrifuge tube, and acidify the filtrate with 3 N sulfuric acid to obtain a copious precipitate. Centrifuge, and discard the clear solution. Wash the precipitate with small portions of water, and allow it to air-dry: the IR absorption spectrum of a potassium bromide dispersion of the precipitate, previously dried over silica gel for 4 hours, exhibits maxima only at the same wavelengths as those of a similar preparation of
USP Gemfibrozil RS.
Dissolution 
711
—
Medium:
0.2 M pH 7.5 phosphate buffer prepared by dissolving 545 g of monobasic potassium phosphate in 5 L of water, adding 131 g of sodium hydroxide, diluting with water to about 19.5 L, and mixing well. Adjust with either 1 N phosphoric acid or 1 N sodium hydroxide to a pH of 7.5, and dilute with water to 20 L; 900 mL.
Apparatus 2:
50 rpm.
Time:
45 minutes.
Procedure—
Determine the amount of C
15H
22O
3 dissolved from UV absorbances at the wavelength of maximum absorbance at about 276 nm on filtered portions of the solution under test, suitably diluted with 1 N sodium hydroxide, in comparison with a Standard solution obtained as follows. Prepare a Standard stock solution of
USP Gemfibrozil RS having a known concentration of about 0.33 mg per mL in
Medium. [NOTE—Initially dissolve the USP Reference Standard in an amount of methanol not to exceed 1% of the volume of the Standard stock solution.
] Quantitatively dilute the Standard stock solution with 1 N sodium hydroxide to obtain a Standard solution having a concentration estimated to correspond to that of the filtered and diluted solution under test.
Tolerances—
Not less than 80% (Q) of the labeled amount of C15H22O3 is dissolved in 45 minutes.
Assay—
Mobile phase, Standard preparation, and System suitability preparation—
Proceed as directed in the Assay under Gemfibrozil.
Assay preparation—
Remove, as completely as possible, the contents of not fewer than 20 Capsules, weigh, and mix. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of gemfibrozil, to a 100-mL volumetric flask, add about 80 mL of methanol, and shake to dissolve. Dilute with methanol to volume, mix, and filter. Transfer 5.0 mL of this clear solution to a 25-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Gemfibrozil. Calculate the quantity, in mg, of C
15H
22O
3 in the portion of Capsules taken by the formula:
500C(rU / rS),
in which the terms are as defined therein.
