Biological Buffers

Buffer Reference Center

Useful pH Ranges of Selected Biological Buffers (25 °C, 0.1M)

Buffers Useful pH Range pKa
(at 20)
pKa
(at 25)
pKa
(at 37)
Reagent Grade BPC
Grade
Ultra
Grade
MES 5.5–6.7 6.16 6.10 5.97 M8250 M2933 M5287
Bis-Tris 5.8–7.2 n/a 6.50 6.36 B9754 B4429 B7535
ADA 6.0–7.2 6.65 6.59 6.46 A9883 n/a A8074
aces 6.1–7.5 6.88 6.78 6.54 A9758 A3594 A7949
PIPES 6.1–7.5 6.80 6.76 6.66 P6757 P1851 P8203
MOPSO 6.2–7.6 n/a 6.90 6.75 M8389 n/a n/a
Bis-Tris Propane 6.3–9.5 n/a 6.8, 9.0 n/a B6755 B4679 B9410
BES 6.4–7.8 7.17 7.09 6.90 B9879 B4554 B6420
MOPS 6.5–7.9 7.28 7.20 7.02 M1254 M3183 M5162
TES 6.8–8.2 7.50 7.40 7.16 T1375 T5691 T6541
HEPES 6.8–8.2 7.55 7.48 7.31 H3375 H4034 H7273
DIPSO 7.0–8.2 n/a 7.60 7.35 D9648 n/a D0306
MOBS 6.9–8.3 n/a 7.60 n/a M3295 n/a n/a
TAPSO 7.0–8.2 n/a 7.60 7.39 T9269 T5566 T0432
Trizma 7.0–9.0 8.20 8.06 7.72 T1503 T6066 T6791
HEPPSO 7.1–8.5 n/a 7.80 6.66 H3137 n/a n/a
POPSO 7.2–8.5 n/a 7.80 7.63 P3405 n/a P7088
TEA 7.3–8.3 n/a 7.80 n/a T1377 n/a n/a
EPPS 7.3–8.7 n/a 8.00 n/a E9502 E0276 E1894
Tricine 7.4–8.8 8.16 8.05 7.80 T0377 T5816 T9784
Gly-Gly 7.5–8.9 n/a 8.20 n/a G1002 G3915 G7278
Bicine 7.6–9.0 8.35 8.26 8.04 B3876 n/a B8660
HEPBS 7.6–9.0 n/a 8.30 n/a H6903 n/a n/a
TAPS 7.7-9.1 8.49 8.40 8.18 T5130 T5316 T9659
AMPD 7.8–9.7 n/a 8.80 n/a A9754 n/a A9074
TABS 8.2–9.6 n/a 8.90 n/a T1302 n/a n/a
AMPSO 8.3–9.7 n/a 9.00 9.10 A6659 n/a A7585
CHES 8.6–10.0 9.55 9.49 9.36 C2885 n/a C8210
CAPSO 8.9–10.3 n/a 9.60 9.43 C2278 n/a C8085
AMP 9.0–10.5 n/a 9.70 n/a A9879 n/a A9199
CAPS 9.7–11.1 10.56 10.40 10.02 C2632 n/a C6070
CABS 10.0–11.4 n/a 10.70 n/a C5580 n/a n/a

 

Trizma Buffer Table – pH vs. Temperature

pH at Temperature   g/L for 0.05 M Solution
5 °C 25 °C 37 °C   Trizma HCL Trizma Base
7.76 7.20 6.91   7.02 0.67
7.89 7.30 7.02   6.85 0.80
7.97 7.40 7.12   6.61 0.97
8.07 7.50 7.22   6.35 1.18
8.18 7.60 7.30   6.06 1.39
8.26 7.70 7.40   5.72 1.66
8.37 7.80 7.52   5.32 1.97
8.48 7.90 7.62   4.88 2.30
8.58 8.00 7.71   4.44 2.65
8.68 8.10 7.80   4.02 2.97
8.78 8.20 7.91   3.54 3.34
8.88 8.30 8.01   3.07 3.70
8.98 8.40 8.10   2.64 4.03
9.09 8.50 8.22   2.21 4.36
9.18 8.60 8.31   1.83 4.65
9.28 8.70 8.42   1.50 4.90
9.36 8.80 8.51   1.23 5.13
9.47 8.90 8.62   0.96 5.32
9.56 9.00 8.70   0.76 5.47

 

Phosphate Buffer Table – 0.2M solution

Potassium 
Phosphate Monobasic Anhydrous g/L
Sodium Phosphate Dibasic
 Heptahydrate g/L
23 °C pH   Potassium Phosphate Monobasic Anhydrous g/L Sodium Phosphate
Dibasic Heptahydrate g/L
23 °C pH
22.4 3.49 5.7   10.80 29.51 6.9
22.08 4.29 5.8   9.36 32.73 7.0
21.60 5.37 5.9   7.92 35.95 7.1
21.05 6.60 6.0   6.72 38.63 7.2
20.40 8.05 6.1   5.52 41.31 7.3
19.56 9.93 6.2   4.56 43.46 7.4
18.60 12.07 6.3   3.84 45.07 7.5
17.64 14.22 6.4   3.12 46.68 7.6
16.44 16.90 6.5   2.52 48.55 7.7
15.00 20.12 6.6   2.04 49.09 7.8
13.56 23.34 6.7   1.68 49.89 7.9
12.24 26.29 6.8   1.27 50.81 8.0

 

Citric Acid – Na2HPO4 Buffer Solutions, pH approx. 2.6–7.61

Citric acid monohydrate, C6H8O7 • H2O, M. wt. 210.14; 0.1M-solution contains 21.01 g/l. Na2HPO4, M. wt. 141.98; 0.2M-solution contains 28.40 g/l, or Na2HPO4 • 2H2O, M. wt. 178.05; 0.2M-solution contains 35.61 g/l.

x ml 0.1M-citric acid and y ml 0.2M-Na2HPO4 mixed.

pH x ml 0.1M-citric acid y ml 0.2-Na2HPO4
2.6 89.10 10.90
2.8 84.15 15.85
3.0 79.45 20.55
3.2 75.30 24.70
3.4 71.50 28.50
3.6 67.80 32.20
3.8 64.50 35.50
4.0 61.45 38.55
4.2 58.60 41.40
4.4 55.90 44.10
4.6 53.25 46.75
4.8 50.70 49.30
5.0 48.50 51.50
5.2 46.40 53.60
5.4 44.25 55.75
5.6 42.00 58.00
5.8 39.55 60.45
6.0 36.85 63.15
6.2 33.90 66.10
6.4 30.75 69.25
6.6 27.25 72.75
6.8 22.75 77.25
7.0 17.65 82.35
7.2 13.05 86.95
7.4 9.15 90.85
7.6 6.35 93.65

 

Citric Acid – Sodium Citrate Buffer Solutions, pH 3.0–6.21

Citric acid monohydrate, C6H8O7 • H2O, M. wt. 210.14; 0.1M-solution contains 21.01 g/l. Trisodium citrate dihydrate, C6H5O7Na3 • 2H2O, M. wt. 294.12; 0.1M-solution contains 29.41 g/l.

x ml 0.1M-citric acid and y ml 0.1M-trisodium citrate mixed.

pH x ml 0.1 M-citric acid y ml 0.1M-trisodium citrate
3.0 82.0 18.0
3.2 77.5 22.5
3.4 73.0 27.0
3.6 68.5 31.5
3.8 63.5 36.5
4.0 59.0 41.0
4.2 54.0 46.0
4.4 49.5 50.5
4.6 44.5 55.5
4.8 40.0 60.0
5.0 35.0 65.0
5.2 30.5 69.5
5.4 25.5 74.5
5.6 21.0 79.0
5.8 16.0 84.0
6.0 11.5 88.5
6.2 8.0 92.0

 

Sodium Acetate – Acetic Acid Buffer Solutions, pH 3.7–5.61

Sodium acetate trihydrate, CH3COONa • 3H2O, M. wt. 136.09; 0.2M-solution contains 27.22 g/l.

x ml 0.2M-NaOAc and y ml 0.2M-HOAc mixed.

pH, 18 °C x ml 0.2M-NaOAc y ml 0.2M-HOAc
3.7 10.0 90.0
3.8 12.0 88.0
4.0 18.0 82.0
4.2 26.5 73.5
4.4 37.0 63.0
4.6 49.0 51.0
4.8 59.0 41.0
5.0 70.0 30.0
5.2 79.0 21.0
5.4 86.0 14.0
5.6 91.0 9.0

 

Na2HPO4 – NaH2PO4 Buffer Solutions, pH 5.8–8.0 at 25 °C1

Na2HPO4 • 2H2O, M. wt. 178.05; 0.2M-solution contains 35.61 g/l. Na2HPO4 • 12H2O, M. wt. 358.22; 0.2M -solution contains 71.64 g/l. NaH2PO4 • H2O, M. wt. 138.01; 0.2M-solution contains 27.6 g/l. NaH2PO4 • 2H2O, M. wt. 156.03; 0.2M-solution contains 31.21 g/l.

x ml 0.2M-Na2HPO4, y ml 0.2M-NaH2PO4; diluted to 100 ml with H2O.

pH, 25 °C x ml 0.2M-Na2HPO4 y ml 0.2M-NaH2PO4
5.8 4.0 46.0
6.0 6.15 43.85
6.2 9.25 40.75
6.4 13.25 36.75
6.6 18.75 31.25
6.8 24.5 25.5
7.0 30.5 19.5
7.2 36.0 14.0
7.4 40.5 9.5
7.6 43.5 6.5
7.8 45.75 4.25
8.0 47.35 2.65

 

Imidazole (glyoxaline) – HCl buffer solutions, pH 6.2–7.8 at 25 °C1

Imidazole, C3H4N2, M. wt. 68.08.

25 ml 0.2M-imidazole (13.62 g/l), x ml 0.2M-HCl, diluted to 100 ml with H2O.

pH, 25 °C x ml 0.2M-HCl
6.2 21.45
6.4 19.9
6.6 17.75
6.8 15.2
7.0 12.15
7.2 9.3
7.4 6.8
7.6 4.65
7.8 3.0

 

Sodium Carbonate – Sodium Bicarbonate Buffer Solutions, pH 9.2–10.81

Na2CO3 • 10H2O, M. wt. 286.2; 0.1M-solution contains 28.62 g/l. NaHCO3, M. wt. 84.0; 0.1M-solution contains 8.40 g/l.

x ml 0.1M-Na2CO3 and y ml 0.1M-Na2HCO3 mixed.

pH x ml 0.1M-Na2CO3 y ml 0.1M-NaHCO3
20 °C 37 °C
9.2 8.8 10 90
9.4 9.1 20 80
9.5 9.4 30 70
9.8 9.5 40 60
9.9 9.7 50 50
10.1 9.9 60 40
10.3 10.1 70 30
10.5 10.3 80 20
10.8 10.6 90 10

 


Helpful Formulas

Percentage by weight (w/v)
(% buffer desired / 100) x final buffer volume (ml) = g of starting material needed.
Molar Solutions
desired molarity x formula weight x solution final volume (L) = grams needed
Henderson-Hasselbach Equation

Reference

  1. Dawson, R. M. C.; Elliot, D. C.; Elliot, W. H.; Jones, K. M. Data for Biochemical Research; 3rd ed., Oxford Science Publ., 1986.

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