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Independent variables and their levels used for Box-Behnken design.
| Variables |
Factors | Levels | ||
|---|---|---|---|---|
| X | −1 | 0 | 1 | |
| Extraction temperature, (°C) | X 1 | 30 | 45 | 60 |
| Extraction time, (min) | X 2 | 60 | 90 | 120 |
| Solid to liquid ratio, (g/mL) | X 3 | 0.5 : 5 | 0.5 : 20 | 0.5 : 35 |
