Lovibond MD100 Mode D'emploi page 31

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
measurement 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. 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.
3. 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).
4. Turbidity (can lead to errors):
Very high levels of calcium hardness (>1000 mg/L CaCO
performing the test. If this occurs add one EDTA tablet to 10 ml of the water sample
prior to run the test.
5. Oxidising agents such as Bromine, Ozone etc. interfere as they react in the same way as
Chlorine.
MD100_2 09/2010
) may lead to turbidity when
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