Limit of meprobamate
Dissolve 100 mg of Carisoprodol in 1.0 mL of chloroform. Dissolve USP Meprobamate RS
in chloroform to obtain a Standard solution containing about 1 mg per mL. Apply a 10-µL portion of the test solution and a separate 5-µL portion of the Standard solution to a suitable thin-layer chromatographic plate (see Chromatography 621
), coated with a 0.25-mm layer of chromatographic silica gel. Allow the spots to dry in a current of air, and develop the chromatogram in a solvent system consisting of a mixture of chloroform and acetone (4:1) 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, allow the solvent to evaporate, and spray the plate alternately with antimony trichloride TS
and a 3 in 100 solution of furfural in chloroform until one or more black spots appear, heat the plate at 110
for 15 minutes, and examine the plate: any spot in the chromatogram of the test solution having an RF
value corresponding to that of meprobamate in the chromatogram of the Standard solution is not darker in color than the meprobamate spot in the chromatogram of the Standard solution (0.5%).
Sodium methoxide titrant
Prepare and standardize as directed for 0.1 N sodium methoxide (in toluene) (see Volumetric Solutions under Reagents, Indicators, and Solutions), except to use 200 mL of methanol to dissolve the sodium metal, to add 750 mL of toluene, and to dilute with methanol to 1000 mL.
Transfer about 400 mg of Carisoprodol, accurately weighed, to a suitable boiling flask, add 10 mL of pyridine, and mix. Add 1 drop of phenolphthalein TS, and titrate with Sodium methoxide titrant
to a permanent pink endpoint. Add 25.0 mL of Sodium methoxide titrant
, connect the flask to a water-cooled condenser, and reflux on a hot plate for 30 minutes. Allow to cool, add 40 mL of alcohol and 7 drops of phenolphthalein TS
, and titrate the excess alkali with 0.1 N hydrochloric acid VS until the pink color disappears. Perform a blank determination (see Residual Titrations
under Titrimetry 541
). Each mL of Sodium methoxide titrant
is equivalent to 26.03 mg of C12