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Biological Buffer Reference Chart
A reference chart for biological buffers, their pKa, effective pH range, and applicable molecular weights. Values based on 25 ° C and 100mM buffer.
| Buffer (100mM) | pKa (25°C) | effective pH range | Molecular Weight (g/mol) |
| ACES | 6.78 | 6.1-7.5 | 182.2 |
| Acetate | 4.76 | 3.6-5.6 | 59.04 |
| ADA | 6.59 | 6.0-7.2 | 190.2 |
| Ammonia | 9.25 | 8.8-9.9 | |
| AMP | 9.69 | 8.7-10.4 | 89.14 |
| AMPD | 8.80 | 7.8-9.7 | 105.14 |
| BES | 7.09 | 6.4-7.8 | 213.2 |
| Bicine | 8.26 | 7.6-9.0 | 163.17 |
| BIS-Tris | 6.46 | 5.8-7.2 | 209.24 |
| Bis-Tris-Propane | 6.8 | 6.3-9.5 | 282.34 |
| Boric Acid (pK1) | 9.23 | 8.5-10.2 | 61.83 |
| Boric Acid (pK2) | 12.74 | ||
| Boric Acid (pK3) | 13.80 | ||
| Cacodylate | 6.27 | 5.0-7.4 | 159.98 |
| CAPS | 10.40 | 9.7-11.1 | 221.32 |
| CAPSO | 9.60 | 8.9-10.3 | 237.32 |
| Carbonate (pK1) | 6.35 | 6.0-8.0 | |
| Carbonate (pK2) | 10.33 | 9.5-11.1 | |
| CHES | 9.5 | 8.6-10.0 | 207.29 |
| Citrate (pK1) | 3.13 | 2.2-6.5 | |
| Citrate (pK2) | 4.76 | 3.0-6.2 | |
| Citrate (pK3) | 6.40 | 5.5-7.2 | |
| DIPSO | 7.52 | 7.0-8.2 | 265.26 |
| Formate | 3.75 | 3.0-4.5 | |
| Glycine (pK1) | 2.35 | 2.2-3.6 | 75.07 |
| Glycine (pK2) | 9.78 | 8.8-10.6 | |
| Glycylglycine | 3.14 | 2.5-3.8 | 132.11 |
| Glycylglycine | 8.25 | 7.5-8.9 | |
| HEPES | 7.48 | 6.8-8.2 | 238.30 |
| HEPPS, EPPS | 8.00 | 7.6-8.6 | 252.33 |
| HEPPSO | 7.85 | 7.1-8.5 | 268.33 |
| Imidazole | 6.95 | 6.2-7.8 | 68.08 |
| Malate (pK1) | 3.40 | 2.7-4.2 | 134.09 |
| Malate (pK2) | 5.13 | 4.0-6.0 | |
| Maleate (pK1) | 1.97 | 1.2-2.6 | 116.10 |
| Maleate (pK2) | 6.24 | 5.5-7.2 | |
| MES | 6.10 | 5.5-6.7 | 195.20 |
| MOPS | 7.14 | 6.5-7.9 | 209.26 |
| MOPSO | 6.87 | 6.2-7.6 | 225.26 |
| Phosphate (pK1) | 2.15 | 1.7-2.9 | |
| Phosphate (pK2) | 7.20 | 5.8-8.0 | |
| Phosphate (pK3) | 12.33 | ||
| PIPES | 6.76 | 6.1-7.5 | 302.36 |
| POPSO | 7.78 | 7.2-8.5 | 406.38 |
| Pyridine | 5.23 | 4.9-5.9 | 79.10 |
| Succinate (pK1) | 4.21 | 3.2-5.2 | 118.09 |
| Succinate (pK2) | 5.64 | 5.5-6.5 | |
| TAPS | 8.40 | 7.7-9.1 | 243.27 |
| TAPSO | 7.61 | 7.0-8.2 | 259.28 |
| Taurine (AES) | 9.06 | 7.4-9.6 | |
| TEA | 7.76 | 7.0-8.3 | 101.19 |
| TES | 7.40 | 6.8-8.2 | 229.25 |
| Tricine | 8.05 | 7.4-8.8 | 179.17 |
| Tris | 8.06 | 7.5-9.0 | 121.14 |