Methods - Lovibond CheckitDirect Mode D'emploi

Methods

GB
Notes Chlorine/Bromine:
1. Vial cleaning:
As many household cleaners (e.g. dishwasher detergent) contain reducing substances,
the subsequent determination of Chlorine/ Bromine 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 /Bromine, 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:
10 mg/l Chlorine using tablets
4 mg/l Chlorine using liquid reagents
22 mg/l Bromine using tablets
can lead to results showing 0 mg/l. In this case, the water sample must be diluted with
water free of Chlorine/ Bromine and the measurement repeated.
6. Turbidity (can lead to errors):
The use of the DPD No. 1 tablet in samples with high Calcium ion contents* and/or high
conductivity* can lead to turbidity of the sample and therefore incorrect measurements.
In this case, the reagent tablet DPD No. 1 High Calcium should be used as an
alternative. Even if turbidity does occur after the DPD No. 3 tablet has been added, this
can be prevented by using the DPD No. 1 HIGH CALCIUM tablet.
* it is not possible to give exact values, because the development of turbidity depends
on the nature of the sample.
7. 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.
Oxidising agents such as Ozone etc. interfere as they react in the same way
as Chlorine/Bromine.
28 CheckitDirect_Cl-Br-pH-CyA-S:4.3-CaH_2c 11/2012
ng.