Table 1 Parameters and levels applied in CCD for d-MSPME optimization
Factors | Low level (−1) | Central point (0) | High level (+ 1) |
|---|---|---|---|
Mass of adsorbent (mg) | 10 | 25 | 41 |
Extraction time (min) | 5 | 10 | 15 |
Desorption time (min) | 5 | 12.5 | 20 |
Eluent volume (µL) | 100 | 550 | 1000 |
pH | 4 | 6.5 | 9 |