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Level of variables selected in the factorial design and response surface methodology.
| Independent variable | Coded variable level |
|||
|---|---|---|---|---|
| Simbol | Low |
Central |
High |
|
| -1 | 0 | 1 | ||
| Sonication time (min) | A | 10 | 20 | 30 |
| Temperature (°C) | B | 30 | 45 | 60 |
| Ethanol/Water (v/v) | C | 70/30 | 80/20 | 90/10 |
| Solid/Liquid (w/v) | D | 1/20 | 1/12.5 | 1/5 |
