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Identity, code unit, coded level and experimental values of the 3 independent variables.
| Independent Variable | Code Unit | Coded Variable Levels | ||
|---|---|---|---|---|
| −1 | 0 | +1 | ||
| aqEtOH concentration (% v/v) 1 | X1 | 25 | 50 | 75 |
| US frequency (kHz) | X2 | 15 | 30 | 45 |
| Extraction duration (min) | X3 | 20 | 40 | 60 |
1 % of aqEtOH concentration in mixture with HPLC grade ultrapure water.
