Lovibond MD 100 Mode D'emploi page 17

Chemical Method
DPD
Appendix
Calibration function for 3rd-party photometers
Conc. = a + b∙Abs + c∙Abs
a
b
c
d
e
f
Interferences
Persistant Interferences
• All oxidising agents in the samples react like chlorine, which leads to higher results.
Removeable Interferences
• Interference from Copper and Iron (III) are eliminated by the addition of EDTA.
• The use of reagent tablets in samples with high Calcium content* and/or high con-
ductivity* can lead to turbidity of the sample and therefore incorrect measurements.
In this case, the alternative reagent tablet DPD No. 1 High Calcium and reagent
tablet DPD No. 3 High Calcium should be used.
*it is not possible to give exact values, because the development of turbidity depends
on the composition and nature of the sample.
• Concentrations above 10 mg/l Chlorine, in the event of using fluid reagents, can lead
to results within the measuring range of up to 0 mg/l. In the event of a high concen-
tration of Chlorine, the sample must be diluted with chlorine-free water. 10 ml of the
diluted sample should be mixed with the reagent and the measurement taken again
(plausibility test).
Interference
CrO
2-
4
MnO
2
EN Method Reference Book 1.0
+ d∙Abs + e∙Abs + f∙Abs
2 3 4
ø 24 mm
-5.41232 ∙ 10
-2
1.78498 ∙ 10
+0
-8.7417 ∙ 10
-2
1.08323 ∙ 10
-1
from / [mg/l]
0.01
0.01
Chlorine T / M100
5
□ 10 mm
-5.41232 ∙ 10
-2
3.83771 ∙ 10
+0
-4.04085 ∙ 10
-1
1.07655 ∙ 10
+0