Biological Buffers

Buffer Reference Center

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

Buffers Useful pH Range pKa
(at 20°C)
pKa
(at 25°C)
pKa
(at 37°C)
Reagent Grade  BioPerformance Certified Grade Pharma Grade
MES 5.5–6.7 6.16 6.10 5.97 M8250 M2933 PHG0003
Bis-Tris 5.8–7.2 n/a 6.50 6.36 B9754 B4429 RES1161B-A7, PHG0004
ADA 6.0–7.2 6.65 6.59 6.46 A9883 n/a n/a
aces 6.1–7.5 6.88 6.78 6.54 A9758 A3594 RES1000A-A7
PIPES 6.1–7.5 6.80 6.76 6.66 P6757 P1851 RES0703P-A7
MOPSO 6.2–7.6 n/a 6.90 6.75 M8389 n/a RES0196M-B7
Bis-Tris Propane 6.3–9.5 n/a 6.8, 9.0 n/a B6755 B4679 PHG0005
BES 6.4–7.8 7.17 7.09 6.90 B9879 B4554 RES1146B-A7
MOPS 6.5–7.9 7.28 7.20 7.02 M1254 M3183 PHG0007
TES 6.8–8.2 7.50 7.40 7.16 T1375 T5691 n/a
HEPES 6.8–8.2 7.55 7.48 7.31 H3375 H4034 RDD002, RES6003H-B7
DIPSO 7.0–8.2 n/a 7.60 7.35 D9648 n/a n/a
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 n/a
Trizma 7.0–9.0 8.20 8.06 7.72 T1503 T6066 RES3137T-A7, RES3193T-A7
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 n/a
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 n/a
Tricine 7.4–8.8 8.16 8.05 7.80 T0377 T5816 RES3077T-A7
Gly-Gly 7.5–8.9 n/a 8.20 n/a G1002 G3915 G0674
Bicine 7.6–9.0 8.35 8.26 8.04 B3876 n/a RES1151B-B7
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 n/a
AMPD 7.8–9.7 n/a 8.80 n/a A9754 n/a n/a
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 n/a
CHES 8.6–10.0 9.55 9.49 9.36 C2885 n/a RES1299C-B7
CAPSO 8.9–10.3 n/a 9.60 9.43 C2278 n/a RES1469C-A7
AMP 9.0–10.5 n/a 9.70 n/a A9879 n/a n/a
CAPS 9.7–11.1 10.56 10.40 10.02 C2632 n/a n/a
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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