The analytes were purified by CARB/SCX solid phase extraction
cartridges which were washed with 5 mL water and 5 mL methanol.
The 5 mL sample extract was loaded under gravity and were
eluted with 5 mL aminated methanol. The extracts were evaporated
to dryness at 50 C with N2 flow for 25e30 min.