Related compounds—
In the chromatogram obtained from the
Assay preparation in the
Assay, the sum of the responses of any peaks detected, other than the major peak due to trioxsalen, is not more than 2.0% of the total of all the peak responses and the response of the peak occurring at retention time relative to trioxsalen of about 0.75 is not more than 1.5% of the total of all responses.
Assay—
Mobile phase—
Prepare a filtered and degassed mixture of methanol and water (70:30). Make adjustments if necessary (see
System Suitability under
Chromatography 
621
).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Trioxsalen RS in tetrahydrofuran to obtain a solution having a known concentration of about 1 mg per mL. Transfer 5.0 mL of this solution to a 100-mL volumetric flask, dilute with
Mobile phase to volume, and mix.
Assay preparation—
Transfer about 100 mg of Trioxsalen, accurately weighed, to a 100-mL volumetric flask, dissolve in tetrahydrofuran, dilute with tetrahydrofuran to volume, mix, and filter. Transfer 5.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-nm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the tailing factor for the trioxsalen peak is not more than 2.0, and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 20 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C
14H
12O
3 in the portion of Trioxsalen taken by the formula:
2000C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Trioxsalen RS in the
Standard preparation, and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
for 6 hours: it loses not more than 0.5% of its weight.