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Sampling
1.
When preparing the sample, chlorine outgassing, e.g. through the pipette or
shaking, must be avoided.
2.
The analysis must take place immediately after taking the sample.
Preparation
1.
Cleaning of vials:
As many household cleaners (e.g. dishwasher detergent) contain reducing
substances, this can lead to lower results with the determination of chlorine.
To avoid measurement errors, the glassware used should be free of chlorine
consumption. To achieve this, all glassware should be placed in a sodium
hypochlorite solution (0.1 g/L) for one hour and then rinsed 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.
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 therefore be adjusted between pH 6 and pH 7 before the
analysis (use 0.5 mol/L sulphuric acid or 1 mol/L sodium hydroxide).
Notes
1.
Evo tablets can be used as an alternative to the corresponding standard tablet (e.g.
DPD No.3 Evo instead of DPD No.3).
EN Method Reference Book 1.0
Chlorine T / M100
EN
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