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PoolDirect 9in1_4i 11/2015
1.1 Methods
Notes:
1. Vial cleaning:
As many household cleaners (e.g. dishwasher detergent) contain reducing substances,
the subsequent determination of 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. Preparing the sample:
When preparing the sample, the lost of Bromine, e.g. by pipetting or shaking, must be
avoided. The analysis must take place immediately after taking the sample.
3. The DPD colour development is carried out at a pH value of 6.2 to 6.5. The reagent
tablet therefore contains 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. Exceeding the measuring range:
Concentrations above 22 mg/l Bromine can lead to results showing 0 mg/l. In this case,
the water sample must be diluted with water free of Bromine. 10 ml of the diluted
sample should be mixed with the reagent and the measurement repeated.
Oxidising agents such as Chlorine, Ozone etc. interfere as they react in the same way
as Bromine.
Precision
An educated operator obtained under laboratory conditions exemplary for 2 different
(one) standard solutions the following standard deviations using different lots of reagent:
0.40 ± 0.04 mg/l; 5.00 ± 0.15 mg/l