Table 1: Formation constants of the binary complexes of DPA at 25 °C and I = 0.1 M ionic strength.
| System | l | p | qa | log βb | Sc |
| DPA | 0 | 1 | 1 | 7.65(0.04) | 4.99E−6 |
| 0 | 1 | 2 | 10.21(0.06) | ||
| Co-DPA | 1 | 1 | 0 | 4.55(0.02) | 4.69E−7 |
| Cu-DPA | 1 | 1 | 0 | 7.65(0.01) | 1.18E−7 |
| Mn-DPA | 1 | 1 | 0 | 4.01(0.04) | 5.31E−7 |
| 1 | 1 | 1 | 8.21(0.02) | ||
| Ni-DPA | 1 | 1 | 0 | 6.88(0.02) | 9.49E−7 |
| Zn-DPA | 1 | 1 | 0 | 5.87(0.03) | 5.68E−7 |
| al, p, and q are the stoichiometric coefficients corresponding to MII, HL, and H+, respectively; | |||||
| bStandard deviation is given in parentheses; | |||||
| cSum of square of residuals. | |||||