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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

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