YSI 900 Chlorine Colorimeter - Manual (Page 13)

13
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. For individual testing of free and total Chlorine, the use of different sets of glassware is
recommended (EN ISO 7393-2, 5.3)
3. Do not use the same sample vial for free and total chlorine without thoroughly rinsing the vial
between the two different tests.
4. 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.
5. 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).
6. exceeding the measuring range:
Concentrations above 2 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.
7. Oxidizing agents such as Bromine, Ozone etc. interfere as they react in the same way as
Chlorine.