Table 2.
Experimental conditions according to the central composite design and observed response values.
| Exp. no. | Run order | A | B | Y 1 | Y 2 | Y 3 |
|---|---|---|---|---|---|---|
| 1 | 8 | −1.00 | −1.00 | 9.21 | 2.52 | 1.6 |
| 2 | 3 | 1.00 | −1.00 | 7.64 | 4.74 | 1.4 |
| 3 | 4 | −1.00 | 1.00 | 8.57 | 3.11 | 1.6 |
| 4 | 11 | 1.00 | 1.00 | 10.41 | 4.69 | 1.8 |
| 5 | 10 | −1.00 | 0.00 | 5.37 | 7.81 | 1.2 |
| 6 | 12 | 1.00 | 0.00 | 12.32 | 5.62 | 1.1 |
| 7 | 9 | 0.00 | −1.00 | 6.35 | 4.59 | 1.5 |
| 8 | 7 | 0.00 | 1.00 | 5.61 | 8.25 | 1.1 |
| 9 | 2 | 0.00 | 0.00 | 4.76 | 7.64 | 1.1 |
| 10 | 1 | 0.00 | 0.00 | 4.79 | 8.01 | 1.2 |
| 11 | 5 | 0.00 | 0.00 | 4.77 | 7.78 | 1.0 |
| 12 | 6 | 0.00 | 0.00 | 4.81 | 8.11 | 1.1 |
| 13 | 13 | 0.00 | 0.00 | 4.78 | 7.85 | 1.1 |
A: methanol concentration (%); B: mobile phase pH.
Y 1: retention times; Y 2: peak resolution; Y 3: peak asymmetry.