Here’s a comparative table of EDTA, DMPS, and DMSA for the top 10 toxic heavy metals, listed in descending order of affinity (based on approximate log K values or practical clinical efficacy) for each chelator.
Stability & Chelation Affinity: EDTA vs. DMPS vs. DMSA
| EDTA (log K) | DMPS (log K) | DMSA (log K) |
| Chromium (Cr³⁺) ~23.0 | Mercury (Hg²⁺) ~35–40 | Mercury (Hg²⁺) ~32–38 |
| Uranium (UO₂²⁺) ~21.0 | Arsenic (As³⁺) ~20–25 | Arsenic (As³⁺) ~18–23 |
| Mercury (Hg²⁺) ~21.5 | Lead (Pb²⁺) ~18–22 | Lead (Pb²⁺) ~18–20 |
| Nickel (Ni²⁺) ~18.6 | Cadmium (Cd²⁺) ~18–20 | Cadmium (Cd²⁺) ~17–18 |
| Lead (Pb²⁺) ~18.0 | Nickel (Ni²⁺) ~13–15 | Nickel (Ni²⁺) ~12–14 |
| Gadolinium (Gd³⁺) ~17.5 | Chromium (Cr³⁺) ~8–10 | Chromium (Cr³⁺) ~8–10 |
| Cadmium (Cd²⁺) ~16.5 | Thallium (Tl⁺) ~8–10 | Thallium (Tl⁺) ~8–10 |
| Aluminum (Al³⁺) ~16.1 | Aluminum (Al³⁺) ~8–11 | Aluminum (Al³⁺) ~8–11 |
| Arsenic (As³⁺) ~8–10 | Gadolinium (Gd³⁺) ~6–10 | Gadolinium (Gd³⁺) ~6–10 |
| Thallium (Tl⁺) ~6–7 | Uranium (UO₂²⁺) ~10–12 | Uranium (UO₂²⁺) ~10–12 |
What These Numbers Mean
The higher the log K, the stronger and more stable the metal–chelating complex.
Log K > 18 = very stable; can effectively chelate and help excrete the metal.
Log K < 10 = weak or unstable; usually ineffective for these metals.
EDTA has moderate to high affinity for many toxic metals, especially lead, cadmium, uranium, and nickel. However, it is ineffective or weakly binding for arsenic, thallium, and gadolinium. This is why other agents like DMSA, DMPS, DTPA, or HOPO chelators are used when higher specificity or stronger binding is required.
DMPS chelates metals through thiol (–SH) groups, which are particularly effective for soft, thiophilic metals like mercury, arsenic, lead, and cadmium, making it one of the most effective chelators for these metals. It is far less effective for lanthanides (like gadolinium), uranium, or chromium, which require chelators like DTPA or investigational HOPOs.
