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NitraLyt
®
700 IQ Calibration and measuring
4 - 15 ba75397d03 12/2004
4.1.8 Calibration procedure, Simple std. add. (4)
Calibration with simple standard addition is carried out in the sample
while adding standard. The volumes of test sample and standard have
to be exactly dosed.
The following appliances are suitable for dosing:
!
Measuring cylinder to determine the volume of the sample
!
Pipette (microliter pipette as necessary) for accurate dosing of the
standard. The higher the concentration of the standard, the more
important it is to measure the amount of calibration standard very
carefully.
Note
Before
calibrating, determine the chloride content of the sample (see
section 4.2.1).
Before calibrating, activate the Cl compens. function and adjust the
chloride content (see section 3.4).
The chloride content of the test sample affects the calibration result.
Conditions and
calibration range for
simple standard
addition
Observe the following points for the simple standard addition:
!
The volume of the standard added to the test sample changes the
test sample. Therefore, the volume of the standard should not be
more than approx. 1 % of the volume of the sample.
Example: With 100 ml sample volume, the added volume should not
be more than 1 ml.
!
Through the addition of standard solution, the nitrate content of the
test sample should be increased at least twofold but not more than
tenfold.
Based on these conditions, the range that can be calibrated is from 0.1
to 22 mg/l NO3-N (or 0.44 to 98 mg/l NO3). If the expected measured
values are outside this range, a different calibration procedure has to
be selected.
Concentration and
quantity of standard
solution
The concentration and quantity of the standard solution to be added
depend on the measuring range expected. They can be determined by
means of the following diagram. The requirements for the simple stan-
dard addition are automatically met while doing so.