Buffer

1. 11/1/2014 Preparation of pH buffer solutions
Delloyd's Lab Tech resources reagents and Solutions
Preparation of pH buffer solutions
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Phosphate and Acetate buffers
The different names for phosphate salts. Standardization buffers pH 4 and pH 7. Ph range of some
buffer systems. Making up buffer solutions by adding an adjuster solution (acid or base) to a known
volume and concentration of a primary salt solution. Potassium hydrogen phosphate, potassium
dihydrogen phosphate, disodium hydrogen phosphate, potassium hydrogen phthalate, sodium
acetate,sodium tetraborate, tris aminomethane.
Related link:
Analysis Buffers
For EDTA titrations
For Fluoride (TISAB)
For Determination of Fe. On this page: Click the links below to jump to the relevant info:
The preparation of pH buffer solutions
acetate buffers
phosphate buffers
solid mixture buffers
Phosphates
Phosphate salts are known by several names and the correct phosphate must be used to prepare buffer
solutions.
One phosphate cannot be substituted for another phosphate. Check formula of salt to be certain.
Formula Name of salt Other names
KH2PO4
potassium dihydrogen
phosphate
potassium dihydrogen orthophosphate
monobasic potassium phosphate
monopotassium phosphate
acid potassium phosphate
potassium biphosphate
K2HPO4
potassium hydrogen
phosphate
dipotassium hydrogen orthophosphate
dipotassium hydrogen phosphate
dibasic potassium phosphate
dipotassium phosphate
K3PO4 potassium phosphate tribasic potassium phosphate
tripotassium phosphate
Standardization buffers
For pH=7.00 :
Add 29.1 ml of 0.1 molar NaOH to 50 ml 0.1 molar potassium dihydrogen phosphate.
Alternatively :
Dissolve 1.20g of sodium dihydrogen phosphate and 0.885g of disidium hydrogen phosphate in 1 liter volume
distilled water.
For pH= 4.00 :
Add 0.1 ml of 0.1 molar NaOH to 50 ml of 0.1 molar potassium hydrogen phthalate .
Alternatively :
Dissolve 8.954g of disodium hydrogen phosphste.12 H2O and 3.4023g of potassium dihydrogen phosphate in 1
liter volume distilled water.
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2. 11/1/2014 Preparation of pH buffer solutions
Range of common buffer systems ¹
Buffering system Useful buffering pH range @
25°C
Hydrochloric acid/ Potassium chloride 1.0 - 2.2
Glycine/ Hydrochloric acid 2.2 - 3.6
Potassium hydrogen phthalate/ Hydrochloric acid 2.2 - 4.0
Citric acid/ Sodium citrate 3.0 - 6.2
Sodium acetate/ Acetic acid 3.7 - 5.6
Potassium hydrogen phtaalate/ Sodium hydroxide 4.1 - 5.9
Disodium hydrogen phthalate / Sodium dihydrogen orthophospate 5.8 - 8.0
Dipotassium hydrogen phthalate / Potassium dihydrogen
5.8 - 8.0
orthophospate
Potassium dihydrogen orthophosphate / sodium hydroxide 5.8 - 8.00
Barbitone sodium / Hydrochloric acid 6.8 - 9.6
Tris (hydroxylmethyl) aminomethane / Hydrochloric acid 7.0 - 9.00
Sodium tetraborate/ Hydrochloric acid 8.1 - 9.2
Glycine/ Sodium hydroxide 8.6 - 10.6
Sodium carbonate/ Sodium hydrogen carbonate 9.2 - 10.8
Sodium tetraborate/ Sodium hydroxide 9.3 - 10.7
Sodium bicarbonate / Sodium hydroxide 9.60 - 11.0
Sodium hydrogen orthophosphate / Sodium hydroxide 11.0 - 11.9
Potassium chloride/ Sodium hydroxide 12.0 - 13.0
Preparing a Buffer Solution ²
This page gives tabulated info on the preparation of buffers by mixing adjusters
with a known volume of the primary salt solution, and made up to 200ml with distilled water.
BUFFERS 1.00 - 9.00
Buffer A :
pH 1.0 - 2.2
Buffer B :
pH 2.2 - 4.00
Buffer C :
pH 4.10 - 5.90
Buffer D :
pH 5.8 - 8.00
Buffer E :
pH 7.0 - 9.00
50 ml 0.2 M
KCl + mls of
0.2 M HCl
100 ml 0.1 M
potassium hydrogen
phthalate + mls of 0.1
M HCl.
100 ml 0.1 M
potassium hydrogen
phthalate + mls of 0.1
M NaOH
. 100 ml 0.1 M
KH2PO4 + mls
of 0.1 M NaOH.
100 ml 0.1 M tris
(hydroxymethyl)
aminomethane +
mls of 0.1 M HCl.
pH mls of
0.2M HCl
added
pH mls of 0.1M HCl
added
pH mls of 0.1M
NaOH added
pH mls of
0.1M
NaOH
added
pH mls of 0.1 M
HCl added
1.00 134.0 2.20 99.0 4.10 2.6 5.80 7.2 7.00 93.2
1.10 105.6 2.30 91.6 4.20 6.0 5.90 9.2 7.10 91.4
1.20 85.0 2.40 84.4 4.30 9.4 6.00 11.2 7.20 89.4
1.30 67.2 2.50 77.6 4.40 13.2 6.10 13.6 7.30 86.8
1.40 53.2 2.60 70.8 4.50 17.4 6.20 16.2 7.40 84.0
1.50 41.4 2.70 64.2 4.60 22.2 6.30 19.4 7.50 80.6
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3. 11/1/2014 Preparation of pH buffer solutions
1.60 32.4 2.80 57.8 4.70 27.2 6.40 23.2 7.60 77.0
1.70 26.0 2.90 51.4 4.80 33.0 6.50 27.8 7.70 73.2
1.80 20.4 3.00 44.6 4.90 38.8 6.60 32.8 7.80 69.0
1.90 16.2 3.10 37.6 5.00 45.2 6.70 38.6 7.90 64.0
2.00 13.0 3.20 31.4 5.10 51.0 6.80 44.8 8.00 58.4
2.10 10.2 3.30 25.8 5.20 57.6 6.90 51.8 8.l0 52.4
2.20 7.8 3.40 20.8 5.30 63.2 7.00 58.2 8.20 45.8
3.50 16.4 5.40 68.2 7.10 64.2 8.30 39.8
3.60 12.6 5.50 73.2 7.20 69.4 8.40 34.4
3.70 9.0 5.60 77.6 7.30 74.0 8.50 29.4
3.80 5.8 5.70 81.2 7.40 78.2 8.60 24.4
3.90 2.8 5.80 84.6 7.50 82.2 8.70 20.6
4.00 0.2 5.90 87.4 7.60 85.6 8.80 17.0
7.70 88.4 8.90 14.0
7.80 90.6 9.00 11.4
7.90 92.2
8.00 93.4
BUFFERS 08 - 13
Buffer F: pH 8.0 - 9.10 Buffer G :
pH 9.2 - 10.80
Buffer H :
pH 9.60 - 11.00
Buffer I :
pH 10.90 - 12.00
Buffer J :
pH 12.00 -
13.00
100 mL 0.025 M
Na2B4O7.10H2O
(borax) + mls of 0.1 M
HCl.
100 mL 0.025 M
Na2B4O7.10H2O
(borax) + mls of 0.1 M
NaOH.
100 mL 0.05 M
NaHCO3 + mls of
0.1 M NaOH.
100 mL 0.05 M
Na2HPO4 + mls
of 0.1 M NaOH.
50 mL 0.2 M
KCl + volume
indicated (in
mL) 0.2 M
NaOH.
pH mls of 0.1M HCl
added
pH mls of 0.1M
NaOH added
pH mls of
0.1M
NaOH
added
pH mls of
0.1M
NaOH
added
pH mls of
0.2M
NaOH
added
8.00 41.0 9.20 1.8 9.60 10.0 10.90 6.6 12.00 12.0
8.10 39.4 9.30 7.2 9.70 12.4 11.00 8.2 12.10 16.0
8.20 37.6 9.40 12.4 9.80 15.2 11.10 10.2 12.20 20.4
8.30 35.4 9.50 17.6 9.90 18.2 11.20 12.6 12.30 25.6
8.40 33.2 9.60 22.2 10.00 21.4 11.30 15.2 12.40 32.4
8.50 30.4 9.70 26.2 10.10 24.4 11.40 18.2 12.50 40.8
8.60 27.0 9.80 30.0 10.20 27.6 11.50 22.2 12.60 51.2
8.70 23.2 9.90 33.4 10.30 30.4 11.60 27.0 12.70 64.4
8.80 19.2 10.00 36.6 10.40 33.0 11.70 32.4 12.80 82.4
8.90 14.2 10.10 39.0 10.50 35.6 11.80 38.8 12.90 106.0
9.00 9.2 10.20 41.0 10.60 38.2 11.90 46.0 13.00 132.0
9.10 4.0 10.30 42.6 10.70 40.4 12.00 53.8
10.40 44.2 10.80 42.4
10.50 45.4 10.90 44.0
10.60 46.6 11.00 45.4
10.70 47.6
10.80 48.5
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4. 11/1/2014 Preparation of pH buffer solutions
Acetate buffer solutions pH 3 - 6 ³
Make up the following solutions
(1) 0.1M acetic acid
(2) 0.1M sodium acetate (tri-hydrate) (13.6g / l)
Mix in the following proportions to get the required ph
ph vol. of 0.1M
acetic acid
vol. of 0.1M
sodium acetate
3 982.3 mls 17.7 mls
4 847.0 mls 153.0 mls
5 357.0 mls 643.0 mls
6 52.2 mls 947.8 mls
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5. 11/1/2014 Preparation of pH buffer solutions
Phosphate buffer solutions ph 7 - 11
Make up the following solutions
(1) 0.1M disodium hydrogen phosphate (14.2g / l)
(2) 0.1M HCl
(3) 0.1M NaOH
Mix in the following proportions to get the required ph
ph vol. of phosphate vol. of 0.1M HCl vol. of 0.1M NaOH
7 756.0 mls 244 mls
8 955.1 mls 44.9 mls
9 955.0 mls 45.0 mls
10 966.4 mls
11 965.3 mls
Addition of acid or base to a salt pH 3 - 11
Here, the primary salt is a solid and is weighed out in grams. A measured amount of 0.1M HCl or NaOH is
added,
then made up to 1 liter to give the relevant buffer solution 4.
pH Salt mixture
Dilute each mixture to 1 liter solution with distilled water
3 10.21g potassium hydrogen phthalate and 223ml of 0.10M HCl
4 10.21g potassium hydrogen phthalate and 1ml of 0.10M HCl
5 10.21g potassium hydrogen phthalate and 226ml of 0.10M NaOH
6 6.81g potassium dihydrogen phOsphate and 56ml of 0.10M NaOH
7 6.81g potassium dihydrogen phosphate and 291ml of 0.10M NaOH
8 6.81g potassium dihydrogen phosphate and 467ml of 0.10M NaOH
9 4.77g sodium tetraborate and 46ml of 0.10M HCl
10 4.77g sodium tetraborate and 183ml of 0.10M NaOH
11 2.10g sodium bicarbonate and 227ml of 0.10M NaOH
1. The Physical and Theoretical Laboratory, Oxford University.
2. "Electrolyte solutions" Robinson, R. A., and Stokes, R. H., 2nd ed., rev. London, Butterworths, 1968.
3. "Practical chemistry" J. Lambert and T.A. Muir, 3rd. Ed. Heineman, London.
4. pdf file, www.bc.ca/bcsc/resources/ (Canadian Teachers Federation).
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Signature: Dhanlal De Lloyd, Chem. Dept, The University of The West Indies, St. Augustine campus
The Republic of Trinidad and Tobago.
Copyright: delloyd2000© All rights reserved.
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6. 11/1/2014 Preparation of pH buffer solutions
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