To test how the process of solvent evaporation affected the yield of EC, EC (1 µg/mL) in MTBE or ethyl acetate was Vers.20020601 added with methyl octadecanoate (abbr. C18:0 FAME, with a final concentration of 1.6 ug/mL). Then the mix solution of EC and C18:0 FAME was separately diluted with MTBE or ethyl acetate to a total volume of 2, 4, 10, 15 mL, dried under nitrogen until the remaining volume approximated to 100 µL. Undiluted sample was directly injected to GC-MS as a control. Two more undiluted samples were over-dried for 1 s and 10 min in separate vials, and then resuspended in 100 µL of corresponding solvent.