stoppered test tubes followed by the addition of 50 µL
of internal standard working solution (10 µg/mL) and
was vortexmixed for 1 min. To this solution, 5 mL of
dichloromethane was added and vortexmixed for
10 min and centrifuged at 3000 rpm for 10 min to ef
fect phase separation. The organic layer was trans
ferred to another tube and evaporated to dryness. Fur
ther, the residue was reconstituted in 250 µL of mobile
phase and subjected to chromatographic analysis.
Chr