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The calculation of the quantities required to prepare Potassium Hydrogen Phthalate (KHP) standard solutions
with various purities are given as an example below:
Name: Potassium Hydrogen Phthalate
Formula: C
8
H
5
KO
4
Carbon, 12 x8 = 96
Oxygen, 16 x4 = 64
Potassium, 39 x 1 = 39
Hydrogen, 1 x5 = 5____________
Total weight = 204.22 g/mol
47% of KHP is Carbon. Purity of the KHP is 99.9%. Therefore, to prepare a 1000 mgC/l standard solution,
add 2.13g of KHP in a flask and add enough deionised water to make it exactly 1 liter solution.
Note that the quantities required change with the % purity of the chemical used. Table 10 below gives the
KHP quantities required at various % purity for the preparation of 1000mgC/l calibration standard.
Table 10 Quantity of KHP required to prepare 1000 mgC/l standard at various purities.
To prepare standard solutions containing more than 1000 mgC/l, the required solvent can be mixed directly
with deionised water. Table 11 below gives the required quantity of KHP for various concentration standard
solutions to be mixed with deionised water and added enough deionised water to make the solution exactly 1
liter.
Table 11 Quantity of KHP required to prepare various concentration TOC standard solutions.
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