Triturate an amount of finely powdered Tablets, equivalent to about 10 mg of trioxsalen, with 100 mL of chloroform, and filter. Apply 5 µL each of this solution and a Standard solution of USP Trioxsalen RS
in chloroform having a known concentration of 100 µg per mL 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, and develop the chromatogram, using methanol as the solvent, 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, and allow the solvent to evaporate. Locate the spots on the plate by viewing under an UV lamp: the RF
value of the principal spot obtained from the test solution corresponds to that obtained from the Standard solution.
Assemble the apparatus, adding 225 mL of Dilute simulated intestinal fluid
to each vessel, and operate the apparatus for 40 minutes. At the end of the 40 minutes, immediately add 675 mL of dehydrated alcohol to each of the vessels. Continue to operate the apparatus for an additional 20 minutes. Determine the amount of C14
dissolved from UV absorbance determined at the wavelength of maximum absorbance at about 252 nm, filtered portions of the solution under test, in comparison with a Standard solution having a known concentration of USP Trioxsalen RS
in the same medium.
Not less than 75% (Q) of the labeled amount of C14H12O3 is dissolved in 60 minutes.
Weigh and finely powder not less than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 5 mg of trioxsalen, to a separator containing 25 mL of water. Extract with three 25-mL portions of chloroform, filtering each extract into a 100-mL volumetric flask. Wash the filter with chloroform, dilute with chloroform to volume, and mix. Transfer 10.0 mL of this solution to a second 100-mL volumetric flask, dilute with chloroform to volume, and mix. Concomitantly determine the absorbances of this solution and a solution of USP Trioxsalen RS
in the same medium having a known concentration of about 5 µg per mL in 1-cm cells at the wavelength of maximum absorbance at about 252 nm, with a suitable spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C14
in the portion of Tablets taken by the formula:
C(AU / AS),
in which C
is the concentration, in µg per mL, of USP Trioxsalen RS
in the Standard solution, and AU
are the absorbances of the solution from the Tablets and the Standard solution, respectively.