Recommended Buffers for Cation Exchange Chromatography*

To use the calculator, enter the buffer's concentration and temperature, then click on the corresponding = button.
The following are the implicit rules of the calculator:

The best buffers (white background)** Less suitable buffers (light brown background)**
Ionic strength at at pH=pKa I ≈ 0.5 C I ≈ 2 C
Concentration range 1 - 500 mM 1 - 130 mM
Temperature range 3 - 37oC 3 - 37oC

pKa0 (25 oC) d(pKa)/dt
ΔH0, kJ/mol
Calculate pKa at
given concentration
and temperature
Buffer name/dissociation type Dissociation step UV Absorption Notes
1.92 -0.0006
1.1
mM   oC
pKa =  
Maleic acid
H2L = H+ + HL-1
Maleic acid, biological buffers structure Opaque up to 270nm Other pKa: 6.23. Can react with strong nucleophiles (e.g. thiols) by Michael addition.
2.148 +0.0047
-8.0
mM   oC
pKa =  
Phosphoric acid
H3L = H+ + H2L-1
H3PO4 = H+ + H2PO4-1 Clear*** Other pKa: 7.198, 12.35. Stabilizes many enzymes. Precipitates bivalent cations.
3.128 -0.0024
4.07
mM   oC
pKa =  
Citric acid
H3L = H+ + H2L-1
Citric acid, biological buffers formula Clear*** Other pKa: 4.761, 6.396. Binds to some proteins. Forms complexes with many metals.
3.40
mM   25oC
pKa =  
Malic acid
H2L = H+ + HL-1
Malic acid, biological buffers structure Clear*** Other pKa: 5.11. Is chiral. Forms complexes with some metals.
3.75
mM   25oC
pKa =  
Formic acid
HL = H+ + L-1
Formic acid, biological buffers formula Clear*** Slightly volatile, usually is sold containing 5-10% of water - difficult to dose in exact amounts.
3.86
mM   25oC
pKa =  
Lactic acid
HL = H+ + L-1
Lactic acid, biological buffers structure Clear*** Is chiral. Usually is sold as ~85% solution in water - difficult to dose in exact amounts.
4.207 -0.0018
3.0
mM   oC
pKa =  
Succinic acid
H2L = H+ + HL-1
Succinic acid, biological buffers formula Clear*** Other pKa: 5.636.
4.756 +0.0002
-0.41
mM   oC
pKa =  
Acetic acid
HL = H+ + L-1
Acetic acid, biological buffers structure Clear*** Volatile.
5.03 (at 20oC)
mM   20oC
pKa =  
Pivalic (trimethylacetic) acid
HL = H+ + L-1
Pivalic (trimethylacetic) acid, biological buffers formula Clear*** Volatile, has bad odor and relatively low solubility in water.
5.11
mM   25oC
pKa =  
Malic acid
HL-1 = H+ + L-2
Malic acid, biological buffers structure Clear*** Other pKa: 3.40. Is chiral. Forms complexes with some metals.
5.39 (at 20oC)
mM   20oC
pKa =  
Picolinic acid
HL± = H+ + L-1
Picolinic acid, biological buffers formula Other pKa: 0.99 at 20oC.
5.636 +0.0002
-0.5
mM   oC
pKa =  
Succinic acid
HL-1 = H+ + L-2
Succinic acid, biological buffers structure Clear*** Other pKa: 4.207.
6.14 -0.0087
14.8
mM   oC
pKa =  
MES
HL± = H+ + L-1
MES, biological buffers formula Clear*** Other pKa: <3. Weekly binds Ca, Mg, Mn. Negligible binding with Cu(II).1,2
6.844 -0.0072
12.23
mM   oC
pKa =  
ADA
HL-1 = H+ + L-2
ADA, biological buffers structure Opaque below 260 nm. Other pKa: 1.59, 2.48. Binds Cu(II), Co(II), Zn(II), Mn(II), Ni(II), Ca(II), weakly binds Mg(II).3,4
6.847 -0.018
30.43
mM   oC
pKa =  
ACES
HL± = H+ + L-1
ACES, biological buffers formula Opaque at 230 nm. Other pKa: <3. Binds Cu(II), Co(II), Zn(II), Nil(II), week binding to Ca(II), Mg(II), negligible binding to Mn(II).1,5
6.90 -0.015
25.0
mM   oC
pKa =  
MOPSO
HL± = H+ + L-1
MOPSO, biological buffers structure Clear*** Other pKa: <2. Chiral, some metal binding.
6.960 -0.0072
12.3
mM   oC
pKa =  
PIPES
(HL±)-1 = H+ + L-2
PIPES, biological buffers formula Clear*** Other pKa: <3. Negligible binding to metals.1,2 Can form radicals, should be avoided in studies of oxidative compounds and redox processes in biochemistry.6,7
7.184 -0.012
21.1
mM   oC
pKa =  
MOPS
HL± = H+ + L-1
MOPS, biological buffers structure Clear*** Other pKa: <2. Negligible binding to metals.2 Partially degrades on autoclaving in the presence of glucose.
7.187 -0.014
24.25
mM   oC
pKa =  
BES
HL± = H+ + L-1
BES, biological buffers formula Clear*** Other pKa: <3. Binds Cu(II), negligible binding to Ca(II), Mg(II) and Mn(II).1
7.198 -0.0022
3.6
mM   oC
pKa =  
Phosphoric acid
H2L-1 = H+ + HL-2
H2PO4-1 = H+ + HPO4-2 Clear*** Other pKa: 2.148, 12.35. Stabilizes many enzymes. Precipitates bivalent cations.
7.50 -0.019
32.13
mM   oC
pKa =  
TES
HL± = H+ + L-1
TES, biological buffers formula Clear*** Other pKa: <3. Binds Cu(II), Co(II), Zn(II), Mn(II). Negligible binding to Ca(II), Mg(II) and Mn(II).1,8
7.564 -0.012
20.4
mM   oC
pKa =  
HEPES
HL± = H+ + L-1
HEPES, biological buffers structure Clear*** Other pKa: <3. Negligible binding to Ca(II), Mg(II) and Mn(II).1 Is oxidized by Cu(II).9 Can form radicals, should be avoided in studies of redox processes in biochemistry.6,7
7.576 -0.018
30.18
mM   oC
pKa =  
DIPSO
HL± = H+ + L-1
DIPSO, biological buffers formula Clear*** Other pKa: <2. Chiral. Binds Co(II), Ni(II).10
7.635 -0.023
39.09
mM   oC
pKa =  
TAPSO
HL± = H+ + L-1
TAPSO, biological buffers structure Clear*** Other pKa: <2. Chiral. Binds Co(II), Ni(II).10
7.85 -0.013
mM   oC
pKa =  
POPSO
(HL±)-1 = H+ + L-2
POPSO, biological buffers formula Clear*** Other pKa: <2. Chiral, is a mixture of two diastereomers. Can form radicals, should be avoided in studies of redox processes in biochemistry.6,7
7.957 -0.013
21.3
mM   oC
pKa =  
EPPS, HEPPS
HL± = H+ + L-1
EPPS, HEPPS, biological buffers structure Clear*** Other pKa: <2. Binds metals. Can form radicals, should be avoided in studies of redox processes in biochemistry.6,7
7.94 -0.014
23.70
mM   oC
pKa =  
HEPPSO
HL± = H+ + L-1
HEPPSO, biological buffers formula Clear*** Other pKa: <2. Chiral.
8.135 -0.018
31.37
mM   oC
pKa =  
Tricine
HL± = H+ + L-1
Tricine, biological buffers structure Clear*** Other pKa: 2.023. Binds Cu(II), Co(II), Zn(II), Ni(II), Cd(II), Pb(II) Ca(II), Mg(II) and Mn(II).1,4 Is photooxidized by flavines.
8.265 -0.026
43.40
mM   oC
pKa =  
Glycylglycine
HL± = H+ + L-1
Glycylglycine, biological buffers formula Clear*** Other pKa: 3.14. Binds Cu(II) Mn(II), weakly binds Ca(II) and Mg(II).1 Is a primary amine, therefore it can form Schiff’s bases with aldehydes/ ketones.
8.334 -0.016
26.34
mM   oC
pKa =  
Bicine
HL± = H+ + L-1
Bicine, biological buffers structure Clear*** Other pKa: 2.0. Binds Cu(II), Co(II), Zn(II), Mn(II), Ca(II), Mg(II).1,8 Is slowly oxidized by ferricyanide.
8.44 -0.024
40.4
mM   oC
pKa =  
TAPS
HL± = H+ + L-1
TAPS, biological buffers formula Clear*** Other pKa: <2. Binds Co(II), Ni(II).10
9.138 -0.025
43.19
mM   oC
pKa =  
AMPSO
HL± = H+ + L-1
AMPSO, biological buffers structure Clear*** Other pKa: <2. Binds Co(II), Ni(II).10 Is chiral.
9.237 -0.008
13.8
mM   oC
pKa =  
Boric acid
HL = H+ + L-1
H3BO3 = H+ + H2BO3-1 Clear*** Forms covalent complexes with mono- and oligosaccharides, ribose subunits of nucleic acids, pyridine nucleotides.
9.43 -0.023
39.55
mM   oC
pKa =  
CHES
HL± = H+ + L-1
CHES, biological buffers formula Clear*** Other pKa: <3.
9.780 -0.026
44.2
mM   oC
pKa =  
Glycine
HL± = H+ + L-1
Glycine, biological buffers structure Clear*** Other pKa: 2.351. Interferes with Bradford protein assay. Is a primary amine, therefore it can form Schiff’s bases with aldehydes/ ketones.
9.825 -0.027
46.67
mM   oC
pKa =  
CAPSO
HL± = H+ + L-1
CAPSO, biological buffers formula Clear*** Other pKa: <2. Is chiral.
10.499 -0.028
48.1
mM   oC
pKa =  
CAPS
HL± = H+ + L-1
CAPS, biological buffers structure Clear*** Other pKa: <2.
10.7
mM   25oC
pKa =  
CABS
HL± = H+ + L-1
CABS, biological buffers formula Clear*** Other pKa: <2.

* Significant deviations exist in the reported values of pKa and other thermodynamic constants of most common buffers due to them being determined by methods of different accuracy. Additionally, many online resources provide pKa values of biological buffers at unspecified or wrongly specified ionic strengths. We attempted to provide the most consistent data available. pKa0, d(pKa)/dt and ΔH0 are compiled mostly from
- CRC Handbook of Chemistry & Physics, 93th edition: Dissociation Constants of Organic Acids and Bases.
- Goldberg, R. N., Kishore, N., Lennen, R. M. J. Phys. Chem. Ref. Data, 31, 2002, 231-370, as well as some other original publications.
If you have have experimentally observed significantly different values, please report them to support@reachdevices.com.

**Temperature dependence of pKa is presumed to be linear.
The best buffers for cation-exchange (white background):
- for concentrations 1 to 200mM, the Debye-Hückel model is used, and the resulting pKa is presented in brown font.
- for concentrations 201 to 500mM, the Davies model is used, and the resulting pKa is presented in blue font.
Less suitable buffers for cation-exchange (light brown background):
- for concentrations 1 to 50mM, the Debye-Hückel model is used, and the resulting pKa is presented in brown font.
- for concentrations 51 to 130mM, the Davies model is used, and the resulting pKa is presented in blue font.
For a detailed explanation of pKa vs pKa0, and formulas used in the calculator, click on this link.

***The buffer is transparent at 200-700 nm range.

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2 - Kandegedara, A., Rorabacher, D. B. Anal. Chem., 1999, 71, 3140-3144.

3 - Lance, E. A., Rhodes, C.W. , Nakon, R. Anal. Biochem., 1983, 133, 492-501.

4 - Nakon, R. Anal. Biochem., 1979, 95, 527-532.

5 - Pope, J. M., Stevens, P. R., Angotti, M. T., Nakon. R. Anal. Biochem., 1980, 103, 214-221.

6 - Grady, J. K., Chasteen, N. D., Harris. D. C., Anal. Biochem., 1988, 173, 111-115.

7 - Kirsch, M., Lomonosova, E. E., Korth, H.-G., Sustmann, R. de Groot, H. The Journal of Biological Chemistry, 1998, 273, 12716-12724.

8 - Nakon, R., Krishnamoorthy. C. R. Science, 1983, 221, 749-750.

9 - Hegetschweiler, K., Saltman, P. Inorg. Chem., 1986, 25, 107-109.

10 - Machado, C. M. M., Gameiro, P., Soares, H. M. V. M. J. Solution Chem., 2008, 37, 603-617.