XD 7500
Operation
77
ba77191e01 - 71310060
04/2018
Example:
Determination of
Chlorophyll a?
according to Nusch
The chlorophyll determination is based on two measurements (before and
after adding an acid) of the optical density (= absorbance) of the extract of an
aqueous sample at 665 nm.
Reformulated
equation
For entry on the photometer, assign names that you can enter in the formula
editor on the photometer to the variables of the equation.
Enter the general method data
Method number, method name, unit etc.
Enter the wavelengths for absorbance measurements (A
x nm
)
Minimum 1, maximum 10
Defining the procedure variables
(K
X
)
(optional)
Procedure variables are used to take into account any influence quanti-
ties that cannot be measured by the photometer.
The values for these procedure variables have to be entered for all mea-
surements with the method, e.g. the temperature or pH value.
Enter the formula to calculate the measurement result
Enter the formula with which you want to calculate the measurement
result in the formula editor.
Enter an additional condition (optional)
Conditions are used to check the measurement result for validity.
The condition is entered with the formula editor.
Chlorophyll a (µg/l) = 29.6 * (A
(before) 665 nm
- A
(after) 665 nm
)*(V
Extract
/
V
Sample
)
with:
A
(before) 665 nm
1. Measurement of the absorbance at 665 nm
(before acid addition)
A
(after) 665 nm
2. Measurement of the absorbance at 665 nm
(after the acid addition)
V
Extract
Volume of the extract (in ml)
V
Sample
Volume of the water sample (in ml)
R = 29.6 * (A
665nm
- A
665nm_2
)*(K
1
/K
2
)
