Tintometer Lovibond MD200 AL 200 Mode D'emploi page 33

Methods
GB
Notes:
1. Vial cleaning:
As many household cleaners (e.g. dishwasher detergent) contain reducing substances,
the subsequent determination of Chlorine may show lower results. To avoid any meas-
urement errors, only use glassware free of Chlorine demand.
Preparation: Put all applicable glassware into Sodium hypochlorite solution (0.1 g/l) for
one hour, then rinse all glassware thoroughly with deionised water.
2. For individual testing of free and total Chlorine, the use of different sets of glassware is
recommended (EN ISO 7393-2, 5.3)
3. Preparing the sample:
When preparing the sample, the lost of Chlorine, e.g. by pipetting or shaking, must be
avoided. The analysis must take place immediately after taking the sample.
4. The DPD colour development is carried out at a pH value of 6.2 to 6.5. The reagents
therefore contain a buffer for the pH adjustment.
Strong alkaline or acidic water samples must be adjusted between pH 6 and pH 7 before
the reagent is added (use 0.5 mol/l Sulfuric acid resp. 1 mol/l Sodium hydroxide).
5. Exceeding the measuring range:
Concentrations above 10 mg/l Chlorine can lead to results showing 0 mg/l. In this case,
the water sample must be diluted with water free of Chlorine and the measurement
repeated.
6. Turbidity (can lead to errors):
The use of the reagent tablets in samples with high Calcium ion contents* and/or high
conductivity* can lead to turbidity of the sample and therefore incorrect measurements.
In this case, the reagent tablets DPD No. 1 High Calcium and DPD No. 3 High Calcium
should be used as an alternative.
* it is not possible to give exact values, because the development of turbidity depends
on the nature of the sample.
7. Oxidising agents such as Bromine, Ozone etc. interfere as they react in the same way as
Chlorine.
Reagent
Set
DPD No. 1 / No. 3
DPD No. 1
DPD No. 3
Kombi-Pack
DPD No. 1 HIGH CALCIUM /
DPD No. 3 HIGH CALCIUM
DPD No. 1 HIGH CALCIUM
DPD No. 3 HIGH CALCIUM
MD200_9 03/2018
Form of reagent/Quantity
Tablet / per 100
inclusive stirring rod
Tablet / 100
Tablet / 100
Tablet / per 100
inclusive stirring rod
Tablet / 100
Tablet / 100
Order-No.
517711BT
511050BT
511080BT
517781BT
515740BT
515730BT
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