Hach BioTector B7000i - Page 66

Page 66
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 deionized water to make it exactly 1 liter solution.
Note that the quantities required change with the % purity of the chemical used. Table 9 below gives the KHP
quantities required at various % purity for the preparation of 1000mgC/l calibration standard.
Table 9 Quantity of KHP required to prepare 1000 mgC/l standard at various purities.
% Purity of KHP
Quantity of KHP (grams)
to prepare 1000 mgC/l Standard
100
2.127
99.9
2.129
99.5
2.138
99.0
2.149
95.0
2.239
90.0
2.364
To prepare standard solutions containing more than 1000 mgC/l, the required solvent can be mixed directly
with deionized water. Table 10 below gives the required quantity of KHP for various concentration standard
solutions to be mixed with deionized water and added enough deionized water to make the solution exactly 1
liter.
Table 10 Quantity of KHP required to prepare various concentration TOC standard solutions.
TOC Standard Solution
Concentration (mgC/l)
Quantity of 99.9% KHP (grams)
to be added into 1 Liter DIW
1000
2.129
1250
2.661
1500
3.194
2000
4.258
5000
10.645
10000
21.290