Calibration standards, Nbs ph buffers – Ionode IJ pH V5.1 User Manual
Page 22
Ionode IJ Instruction Manual
22
4.5. Calibration Standards
4.5.1. NBS pH Buffers
pH 4.01: 0.05M Potassium Hydrogen Phthalate
Dissolve
10.12g
of
potassium
hydrogen
phthalate in distilled water and make up to 1L.
pH 6.87: 0.025M Potassium Dihydrogen
Phosphate / 0.025M Disodium Hydrogen
Phosphate
Dry each salt at 120
o
C for 2 hours and then
cool in a desiccator. Dissolve 3.533g disodium
hydrogen phosphate and 3.388g potassium
dihydrogen phosphate in distilled water and
make up to 1L.
pH 7.413: 0.008695M Potassium Dihydrogen
Phosphate / 0.03043M Disodium Hydrogen
Phosphate
Prepare salts as above and dissolve 1.179g
potassium dihydrogen phosphate and 4.302g
disodium hydrogen phosphate in distilled water
and make up to 1L.
pH
9.18:
0.01M
Sodium
Tetraborate
Decahydrate
Dissolve
3.80g
of
sodium
tetraborate
decahydrate (borax) in distilled water and make
up to 1L. This solution is susceptible to pH
change from carbon dioxide and should be
prepared fresh regularly.
pH 10.01: 0.025M Sodium Bicarbonate /
0.025M Sodium Carbonate
Use anhydrous reagent grade salts to prepare
this
buffer.
Dissolve
2.092g
of
sodium
bicarbonate and 2.640g of sodium carbonate in
distilled water and make up to 1L.