This table of frequently used biological buffers gives the pKa value at 20 °C, 25 °C, and 37 °C as well as the useful pH range of each buffer. The buffers are listed in order of increasing pH. Column definitions for the table are as follows.
Column heading | Definition |
Acronym | Common acronym of the biological buffer |
Name | Systematic name of the biological buffer |
Mol. wt. | Molecular weight of the biological buffer |
pKa(20 °C) | Negative logarithm of the acid dissociation constant at 20 °C |
pKa(25 °C) | Negative logarithm of the acid dissociation constant at 25 °C |
pKa(37 °C) | Negative logarithm of the acid dissociation constant at 37 °C |
Useful pH range | Range of pH for which buffer is useful |
The table is reprinted with permission of Sigma Chemical Company, St. Louis, MO.
Acronym | Name | Mol. wt. | pKa(20 °C) | pKa(25 °C) | pKa(37 °C) | Useful pH range |
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MES | 2-(N-Morpholino)ethanesulfonic acid | 6.16 | 6.10 | 5.97 | 5.5–6.7 | |
BIS TRIS | Bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane | n/a | 6.50 | 6.36 | 5.8–7.2 | |
ADA | N-(2-Acetamido)-2-iminodiacetic acid | 6.65 | 6.59 | 6.46 | 6.0–7.2 | |
ACES | 2-[(2-Amino-2-oxoethyl)amino]ethanesulfonic acid | 182.199 | 6.88 | 6.78 | 6.54 | 6.1–7.5 |
PIPES | Piperazine-N,N´-bis(2-ethanesulfonic acid) | 6.80 | 6.76 | 6.66 | 6.1–7.5 | |
MOPSO | 3-(N-Morpholino)-2-hydroxypropanesulfonic acid | n/a | 6.90 | 6.75 | 6.2–7.6 | |
BIS TRISPROPANE | 1,3-Bis[tris(hydroxymethyl)methylamino]propane | n/a | 6.8 | n/a | 6.3–9.5 | |
BES | N,N-Bis(2-hydroxyethyl)-2-aminoethanesulfonic acid | 213.252 | 7.17 | 7.09 | 6.90 | 6.4–7.8 |
MOPS | 3-(N-Morpholino)propanesulfonic acid | 7.28 | 7.20 | 7.02 | 6.5–7.9 | |
TES | N-Tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid | 7.50 | 7.40 | 7.16 | 6.8–8.2 | |
HEPES | N-(2-Hydroxyethyl)piperazine-N´-(2-ethanesulfonic acid) | 7.55 | 7.48 | 7.31 | 6.8–8.2 | |
DIPSO | 3-[N,N-Bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid | n/a | 7.60 | 7.35 | 7.0–8.2 | |
MOBS | 4-(N-Morpholino)butanesulfonic acid | n/a | 7.60 | n/a | 6.9–8.3 | |
TAPSO | 3-[N-Tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid | n/a | 7.60 | 7.39 | 7.0–8.2 | |
TRIZMA | Tris(hydroxymethyl)methylamine | 121.135 | 8.20 | 8.06 | 7.72 | 7.0–9.1 |
HEPPSO | N-(2-Hydroxyethyl)piperazine-N´-(2-hydroxypropanesulfonic acid) | n/a | 7.80 | 6.66 | 7.1–8.5 | |
POPSO | Piperazine-N,N´-bis(2-hydroxypropanesulfonic acid) | n/a | 7.80 | 7.63 | 7.2–8.5 | |
TEA | Tris(2-hydroxyethyl)amine | 149.188 | n/a | 7.80 | n/a | 7.3–8.3 |
EPPS | 4-(2-Hydroxyethyl)-1-piperazinepropanesulfonic acid | 8.00 | n/a | 7.3–8.7 |