Table 2.
Box-Behnken experimental design matrixes of the selected independent variables and studied responses.
| Number of experiments | Factors levels | Responses | ||||
|---|---|---|---|---|---|---|
| x 1 | x 2 | x 3 | y 1 | y 2 | y 3 | |
| 1 | 3.8 | 0.6 | 40 | 3.06 | 1.27 | 1.72 |
| 2 | 4.2 | 0.6 | 40 | 2.79 | 1.33 | 1.51 |
| 3 | 3.8 | 0.8 | 40 | 3.66 | 1.40 | 1.60 |
| 4 | 4.2 | 0.8 | 40 | 4.02 | 1.04 | 1.41 |
| 5 | 3.8 | 0.7 | 35 | 3.12 | 1.51 | 1.58 |
| 6 | 4.2 | 0.7 | 35 | 4.25 | 1.07 | 1.43 |
| 7 | 3.8 | 0.7 | 45 | 3.91 | 1.37 | 1.38 |
| 8 | 4.2 | 0.7 | 45 | 2.58 | 1.52 | 1.32 |
| 9 | 4.0 | 0.6 | 35 | 3.59 | 1.39 | 1.59 |
| 10 | 4.0 | 0.8 | 35 | 3.85 | 1.30 | 1.40 |
| 11 | 4.0 | 0.6 | 45 | 3.05 | 1.44 | 1.56 |
| 12 | 4.0 | 0.8 | 45 | 3.25 | 1.35 | 1.78 |
| 13 | 4.0 | 0.7 | 40 | 4.58 | 1.06 | 2.06 |
| 14 | 4.0 | 0.7 | 40 | 4.48 | 1.12 | 2.15 |
| 15 | 4.0 | 0.7 | 40 | 4.28 | 1.03 | 2.12 |
x 1: pH of mobile phase; x2: flow rate (mL/min); x3: content of acetonitrile (%); y1: Rs between impurity G and SIM; y2: tailing factor SIM (T); and y3: Rs between impurities B and C.