EC was determined according to the AOAC (2000) first action
method with minor modifications (Wu et al., 2012). In brief, the
d5-ethyl carbamate was used as an internal standard. A 2.0-g wine
sample containing 100-lL 1.0 lg/mL d5-ethyl carbamate was
added to a centrifuge tube and vortexed for 1 min. Using a diatomite solid-phase extraction column, the analyte was eluted from
the mixture with 10 mL of 5% ethyl acetate after 10 min of short
static stretches. The collected elutate was dried by anhydrous
sodium sulfate, and concentrated using N2 flow at 30 C. The analyte
was further diluted with methanol to a final volume of 1 mL
for GC/MS. All samples were measured three times and the data
were presented as the average of the three measured valu