4 Calibration
20
How to prepare span calibration solution of acid potassium phthalate standard
solution (standard solution for UV calibration)
Normally calibration with the common span calibration solution is available; also, UV
calibration with acid potassium phthalate is possible.
Preparation
1.
Determine the requirement of acid potassium phthalate from the following table
according to the measurement range.
Note
The calibration solution of acid potassium phthalate has a temperature characteristic. The
temperature characteristic is (4.5 × 10
-3
)/°C at a temperature of 5°C to 30°C. Measure the temperature
of calibration solution to calculate the light absorption during calibration.
Calculation method:
Light absorption of calibration solution = Light absorption of calibration solution at a temperature of
25°C × (1 + (temperature of calibration solution
25) × 0.0045)
(The above table shows light absorptions also at 20°C and 30°C as a reference.)
2.
Measure the requirement of acid potassium phthalate (special grade chemicals)
following the table above.
3.
Pour approximately 500 mL of the zero solution (distilled water) into the 1 L beaker,
and add the measured acid potassium phthalate to dissolve thoroughly.
Tip
The acid potassium phthalate dissolves easily when setting the temperature of the zero solution from
40°C to 50°C.
Acid potassium phthalate:
using the special grade chemicals, dried for 1 hour at a
temperature of 120°C, and cooled in desiccators
Zero solution (distilled water): approximately 3 L
1 L Beaker:
1
2 L Measuring flask:
1
Electronic balance:
1 (Accuracy shall be within 1 mg.)
Cleaning bottle:
1
UV measurement
range
Requirement of
acid potassium
phthalate when
compounded in
2 L
Concentration
of span
calibration
solution
Light absorption
when the
temperature of
calibration
solution is 25°C
(absorption
factor)
Light absorption
when the
temperature of
calibration
solution is 20°C
(absorption
factor)
Light absorption
when the
temperature of
calibration
solution is 30°C
(absorption
factor)
0.1 Abs to 0.5 Abs
(10 m
-1
to 50 m
-1
)
100 mg
50 mg/L
0.44 Abs
(44 m
-1
)
0.43 Abs
(43 m
-1
)
0.45 Abs
(45 m
-1
)
0.6 Abs to 1.0 Abs
(60 m
-1
to 100 m
-1
)
200 mg
100 mg/L
0.87 Abs
(87 m
-1
)
0.85 Abs
(85 m
-1
)
0.89 Abs
(89 m
-1
)
1.1 Abs to 2.5 Abs
(110 m
-1
to 250 m
-1
)
400 mg
200 mg/L
1.74 Abs
(174 m
-1
)
1.70 Abs
(170 m
-1
)
1.78 Abs
(178 m
-1
)
2.6 Abs to 5.0 Abs
(260 m
-1
to 500 m
-1
)
800 mg
400 mg/L
3.48 Abs
(348 m
-1
)
3.40 Abs
(340 m
-1
)
3.56 Abs
(356 m
-1
)
