2.6. Calculation procedures
For all the employed extraction methods, total yields were calculated
as the ratio between the total extract mass and the raw
material mass, on a dry basis. For the HPE experiments, the total
extract mass included the fractions collected during the extraction
kinetic, the ones retained in the trap and adsorbent column, as well
as the one recovered from tubing line cleaning with EtOH.
The overall extraction curves were set up considering the
accumulated mass of extract (collected at a fixed time interval).
Therefore, the extract fractions retained in the trap and adsorbent
column, as well as the ones collected in the cleaning process
were not considered for the kinetic representations. Each overall
1st step and 2nd step F-HPE curve, and NF-HPE curve was fitted by
a curve formed by two straight lines using the fminsearch function
of Matlab (R2007a), as described by Seabra et al. [30]. The kinetic
parameters of the constant extraction rate (CER) period were calculated
according to Rodrigues et al. [34]: (i) mass transfer rate for
the constant extraction rate period, MCER; (ii) mass ratio of solute
in solvent phase at measuring-cell outlet, YCER, and (iii) duration of
the constant extraction rate period, tCER.