Lovibond MiniDirect Cl Instrucciones página 22

Methods
GB
Notes Chlorine:
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 contamination .
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 . Do not use the same sample vial for free and total chlorine without thoroughly rinsing
the vial betweeen the two different tests .
4 . Preparing the sample:
When preparing the sample, the escape of Chlorine gases, e .g . by pipetting or shaking,
must be avoided . The analysis must take place immediately after taking the sample .
5 . 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) .
6 . Concentrations above
2 mg/l Chlorine using powder packs with method P1
8 mg/l Chlorine using powder packs with method P2
can lead to results showing 0 mg/l . In this event, the water sample must be diluted with
water free of Chlorine and the measurement repeated .
Oxidizing agents such as Bromine, Ozone etc . interfere as they react in the same way
as Chlorine .
22 MiniDirect_Cl_1 09/2008