Next, analytes were extracted from
the samples by adding 15 mL of ethyl acetate/formic acid (99:1, v/
v) and shaking for 30 min.
The mixture was centrifuged for 10 min
at 4050g.
Subsequently, the extracts were evaporated to dryness at
room temperature under a nitrogen stream.
The residue was dissolved
with 400 lL of a mixture of Milli-Q water/MeOH (50:50,
v/v) and placed in a 1.5 mL Eppendorf tube.
500 lL of hexane
was added and the mixture was centrifuged for 15 min at
24960g.
Finally, the underlying aqueous phase was separated and
10 lL injected into the ultra high performance liquid chromatograph
(UHPLC) system.