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Calculate buffer compositions for any target pH. Get acid/base ratios and buffer capacity estimates.
HEPES acid / HEPES sodium
pKa
7.48
Range
6.8–8.2
Base component
22.7 mM
Acid component
27.3 mM
NaH₂PO₄ / Na₂HPO₄
pKa
7.2
Range
5.8–8
Base component
30.7 mM
Acid component
19.3 mM
MOPS acid / MOPS sodium
pKa
7.2
Range
6.5–7.9
Base component
30.7 mM
Acid component
19.3 mM
Tris base / Tris-HCl
pKa
8.06
Range
7–9
Base component
9.0 mM
Acid component
41.0 mM
CO₂/H₂CO₃ / NaHCO₃
pKa
6.35
Range
5.1–7.1
Base component
45.9 mM
Acid component
4.1 mM
MES acid / MES sodium
pKa
6.15
Range
5.5–6.7
Base component
47.3 mM
Acid component
2.7 mM
CH₃COOH / CH₃COONa
pKa
4.76
Range
3.7–5.6
Base component
49.9 mM
Acid component
0.1 mM
Citric acid / Na₃Citrate
pKa
4.76
Range
3–6.2
Base component
49.9 mM
Acid component
0.1 mM
Buffer calculations use Henderson-Hasselbalch equation. Actual pH may vary with temperature, ionic strength, and CO₂ absorption. Verify with a pH meter. For research purposes only.