Recommended Buffers for Anion 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
5.23 -0.014 mM   oC
pKa =  
Pyridine
HL+ = H+ + L
pyridine, biological buffers stucture 275nm Volatile and toxic.
5.333 -0.018
31.11
mM   oC
pKa =  
Piperazine
H2L+2 = H+ + HL+
piperazine, biological buffers formula Clear*** Other pKa: 9.731.
6.05 -0.017
29.5
mM   oC
pKa =  
L-Histidine
H2L+ = H+ + HL±
Histidine, biological buffers structure 235nm Other pKa: 1.80, 9.34. Chiral. Forms complexes with Me2+, forms complexes with itself. It is a primary amine, and therefore can form Schiff’s bases with aldehydes/ ketones.
6.484 -0.017
28.4
mM   oC
pKa =  
Bis-tris
HL+ = H+ + L
Bis-tris, biological buffers formula Clear*** Binds Ca(II), Sr(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II); weakly binds Mg(II), Ba(II), Mn(II).1
6.65 -0.03
mM   oC
pKa =  
Bis-tris propane
H2L+2 = H+ + HL+
Bis-tris propane, biological buffers structure Clear*** Other pKa: 9.11.
6.993 -0.021
36.64
mM   oC
pKa =  
Imidazole
HL+ = H+ + L
Imidazole, biological buffers formula 235nm Forms complexes with Me2+, and forms complexes with histidine. Strongly nucleophilic, catalyzes wide range of chemical transformations.
7.77 -0.016
27.4
mM   oC
pKa =  
N-Ethylmorpholine
HL+ = H+ + L
N-Ethylmorpholine, biological buffers structure Clear***
7.762 -0.020
33.6
mM   oC
pKa =  
TEA (Triethanolamine)
HL+ = H+ + L
TEA (Triethanolamine), biological buffers formula Clear*** Binds Co(II), Ni(II), Cu(II), Zn(II), Cd(II).1 Can form radicals in the presence of strong oxidants, exercise caution during studies of redox processes.
8.072 -0.028
47.45
mM   oC
pKa =  
Tris
HL+ = H+ + L
Tris, biological buffers structure Clear*** Binds Cu(II), Ni(II).1,2 Binds Co(II), Zn(II), Cd(II), Pb(II); weakly binds Ca(II), Mg(II), Ba(II), Mn(II).1 It is a primary amine, and therefore can form Schiff’s bases with aldehydes/ ketones. Inactivates DEPC. Is involved in some enzymatic reactions (e.g. alkaline phosphatase).
8.50 -0.022
mM   oC
pKa =  
Morpholine
HL+ = H+ + L
Morpholine, biological buffers formula Clear***
8.54 -0.028
mM   oC
pKa =  
N-Methyldiethanolamine
HL+ = H+ + L
N-Methyldiethanolamine, biological buffers structure Clear***
8.801 -0.029
49.85
mM   oC
pKa =  
AMPD (2-amino-2-methyl-1,3-propanediol)
HL+ = H+ + L
AMPD (2-amino-2-methyl-1,3-propanediol), biological buffers formula Clear*** It is a primary amine, and therefore can form Schiff’s bases with aldehydes/ ketones.
8.883 -0.026
42.08
mM   oC
pKa =  
Diethanolamine
HL+ = H+ + L
Diethanolamine, biological buffers structure Clear*** Binds Ni(II), Cu(II), Zn(II), Cd(II).1
9.498 -0.030
50.52
mM   oC
pKa =  
Ethanolamine
HL+ = H+ + L
Ethanolamine, biological buffers formula Clear*** Binds Co(II), Ni(II), Cu(II), Zn(II), Cd(II); weakly binds Mn(II).1 It is a primary amine, and therefore can form Schiff’s bases with aldehydes/ ketones.
9.694 -0.032
54.05
mM   oC
pKa =  
AMP (2-amino-2-methyl-1-propanol)
HL+ = H+ + L
AMP (2-amino-2-methyl-1-propanol), biological buffers structure Clear*** It is a primary amine, and therefore can form Schiff’s bases with aldehydes/ ketones.
9.731 -0.025
42.89
mM   oC
pKa =  
Piperazine
HL+ = H+ + L
Piperazine, biological buffers formula Clear*** Other pKa: 5.333.
10.55 -0.026
mM   oC
pKa =  
1,3-Diaminopropane
HL+ = H+ + L
1,3-Diaminopropane, biological buffers structure Clear*** Other pKa: 8.88. Forms strong complexes with many metals. It is a primary amine, and therefore can form Schiff’s bases with aldehydes/ ketones.
11.123 -0.031
mM   oC
pKa =  
Piperidine
HL+ = H+ + L
Piperidine, biological buffers structure Clear***

* 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.

1 - Scheller, K. H., Abel, T. H., Polanyi, P. E., Wenk, P. K., Fischer, B. E., Sigel. H. Eur. J. Biochem., 1980, 107, 455-466.

2 - Bai, K. -S., Martell. A. E., J. Inorg. Nucl. Chem., 1969, 31, 1697–1707.