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Independent variables, dependent variables, and levels of the face centered central composite design.
| Factor | Symbol | Level (−1) | Level (0) | Level (+1) |
|---|---|---|---|---|
| Independent | ||||
| Methanol concentration (%) | A | 10 | 20 | 30 |
| Mobile phase pH | B | 2.5 | 3.5 | 4.0 |
| Dependent | ||||
| Retention time | Y 1 | |||
| Peak resolution | Y 2 | |||
| Peak asymmetry | Y 3 |
