| Molar absorptivity of Fe (II)-MD complex | |||
| pH | Wavelength | ||
| 430 nm | 615 nm | 730 nm | |
| 4.0 | 1410 | 1126 | 1066 |
| 4.5 | 2030 | 2016 | 1740 |
| 5.0 | 2460 | 2848 | 1770 |
| 5.5 | 2642 | 3498 | 1912 |