3.3.3. Completeness of ethanol mass transfer to headspace
The evaluation of the completeness of ethanol mass transfer to headspace was conducted at a selected equilibration temperature of 105 °C and an equilibration time of 3 min. Since the partition coefficients (or H) of ethanol at higher temperature (closed to or above the boiling point) are not available, the completeness of ethanol mass transfer in EF was evaluated by the following procedures: i.e., the liquor sample was added on a piece of the filter paper that was placed in a closed vial for the first headspace GC measurement; then the filter paper was removed from the vial and placed to another sample vial for a second HS-GC measurement under the same conditions. The GC signal of the second headspace measurement is much smaller than that found in the first measurement, qualitatively indicating that more ethanol mass has been transferred to headspace during the first equilibration. The ratio (R) of the GC signal counts from these two headspace measurements, i.e., R = A2/A1, is a measure of the effectiveness of ethanol mass transfer in the first headspace equilibration can then be calculated.
equation(4)Eff (%)=(1−R)×100Eff (%)=(1−R)×100The results show that the efficiency of the ethanol mass transfer is 99% at the first headspace equilibration, indicating that the near-complete ethanol evaporation has been achieved under the given experiment conditions.