YSI 900 Chlorine Colorimeter - Manual (Page 11)

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ENGLISH
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 deionized water.
2. preparing the sample:
When preparing the sample, the loss of Chlorine, e.g. by pipetting or shaking, must be avoided.
The analysis must take place immediately after taking the sample.
3. The DPD color 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
3
) may lead to turbidity when performing
the test. If this occurs add one EDTA tablet to 10 ml of the water sample prior to run the test.
5. Oxidizing agents such as Bromine, Ozone etc. interfere as they react in the same way as
Chlorine.