Procedure
Pipet 1-mL portions of the
Standard preparation and the
Assay preparation into separate 100-mL volumetric flasks, dilute with
Borate solution to volume, and mix. Transfer 5.0-mL portions of each of the resulting solutions to separate low-actinic glass, 50-mL volumetric flasks, and add 15 mL of
Borate solution and 15.0 mL of
Sodium dithionite solution. Pass nitrogen through the solutions, seal the flasks with nitrogen-filled balloons, and heat in a water bath for 30 minutes. Cool the flasks for 15 minutes in a water bath thermostatically controlled at 20
. Dilute the solutions with
Borate solution to volume, and mix. Determine without delay the fluorescence intensities of the resulting solutions in a fluorometer at an excitation wavelength of 392 nm and an emission wavelength of 505 nm, the time elapsed between the addition of the
Sodium dithionite solution and the measurement being the same for the two solutions. Calculate the quantity, in mg, of sennosides in the Sennosides taken by the formula:
25C(IU / IS),
in which
C is the concentration, in mg per mL, of
USP Sennosides RS, corrected for loss on drying, in the
Standard preparation, and
IU and
IS are the fluorescence values observed for the solutions from the
Assay preparation and the
Standard preparation, respectively.