| H+ (mol∙L−1) | Separation factor (SF) Zr/Hf | ||
| TBP | CYANEX®923 | TBP/CYANEX®923 | |
| 1.0 | 0.7 | 1.7 | 3.5 |
| 2.0 | 1.6 | 4.4 | 13.6 |
| 3.0 | 3.5 | 10 | 8.6 |
| 4.0 | 4.7 | 5.9 | 8.5 |
| 5.0 | 13.1 | 13.5 | 6.7 |
| 7.0 | 51.3 | 25.7 | 14.6 |
| 10 | 51.0 | 15.9 | 15.5 |