Table 2 Screening variables and their levels (in coded and actual) used for 32 factorial design
Independent variables | Level used, | actual (coded) | |
|---|---|---|---|
(− 1) | (0) | (+ 1) | |
X1 = Flow rate (ml/min) | 1 | 1.1 | 1.2 |
X2 = Temperature (°C) | 20 | 22.5 | 25 |
X3 = Methanol (%) | 80 | 82.5 | 85 |