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
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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
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Phosphate Buffer Table – 0.2M solution

Sodium Phosphate Monobasic Anhydrous g/L	Sodium Phosphate Dibasic Heptahydrate g/L	23 °C pH		Sodium 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
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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
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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
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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
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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-NaH2PO2
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
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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
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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
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Henderson-Hasselbach Equation

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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.