Tintometer Lovibond MD200 Mode D'emploi page 37

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. 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 4 mg/l Chlorine using liquid reagents 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. After using liquid reagents replace the bottle caps securely noting the colour codi
Store the reagent bottles in a cool, dry place ideally between 6°C and 10 °C.
7. Oxidising agents such as Bromine, Ozone etc. interfere as they react in the same way as
Chlorine.
MD200_1b 11/2011
ng.
37