Chlorine, 0.01 - 6.0 Mg/L Cl - Grundfos DIT-L Bedienungsanleitung

7.3 Chlorine, 0.01 - 6.0 mg/l Cl

Start the photometer and select method.
See section 6.1 Start.
7.3.1 Important notes
• 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.
• For individual testing of free and total chlorine, the use of
different sets of glassware is recommended.
See EN ISO 7393-2, section 5.3.
• When preparing the sample, the escape of chlorine gas,
e.g. by pipetting or shaking, must be avoided. The analysis
must take place immediately after taking the sample.
• 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 sulphuric acid and 1 mol/l sodium hydroxide,
respectively).
• For concentrations between 6.0 and 10 mg/l, the photometer
shows that the measuring range [Hi] has been exceeded.
Concentrations above 10 mg/l chlorine 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
(plausibility test).
• Turbidity can lead to errors:
The use of the DPD No. 1 tablet (No 95727747) 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 (No 95727748) should be used as an alternative.
Even if turbidity does occur after the DPD No. 3 tablet
(No 95727750) tablet has been added, this can be prevented
by using the DPD No. 1 high calcium tablet. (No 95727748).
*) It is not possible to give exact values, because the
development of turbidity depends on the nature of the
sample.
• All oxidising agents in the samples interfere as they react in
the same way as chlorine.
7.3.2 Free chlorine
1. Fill a clean vial (∅24) with 10 ml of the water
0.0.0
sample and perform zero setting. See
section 6.2 Zero
2. Remove the vial from the sample chamber
and empty it, leaving a few drops in the vial.
3. Add one DPD No. 1 tablet (No 95727747) or
DPD No. 1 high calcium straight from the foil
to the water sample and crush the tablets
using a clean stirring rod.
4. Add the water sample to the 10 ml mark.
5. Close the vial tightly with the cap and swirl
gently several times until the tablets are
dissolved.
6. Place the vial in the sample chamber
correctly. See fig. 3.
7. Press the [Zero/Test] key.
Zero/Test
The method symbol flashes for approx.
CL 6
3 seconds.
"RESULT" appears in the display in mg/l free
RESULT
chlorine.
10
CL 6
2
setting.
7.3.3 Total chlorine (free and combined differentiated)
1. At first, carry out the method described in
section 7.3.2 Free
2. Add one DPD No. 3 tablet (No 95727750)
straight from the foil to the same water
sample and crush the tablet using a clean
stirring rod.
3. Close the vial tightly with the cap and swirl
gently several times until the tablet is
dissolved.
4. Place the vial correctly in the sample
chamber. See fig. 3.
5. Wait for a reaction period of 2 minutes.
!
Countdown can be activated.
See section
6. Press the [Zero/Test] key.
Zero/Test
The method symbol flashes for approx.
CL 6
3 seconds.
"RESULT" appears in the display in mg/l total
RESULT
chlorine.
7.3.4 Total chlorine (not differentiated)
1. Fill a clean vial (∅24) with 10 ml of the water
0.0.0
sample and perform zero setting. See
section 6.2 Zero
2. Remove the vial from the sample chamber
and empty it, leaving a few drops in the vial.
3. Add one DPD No. 4 tablet (No 95727751)
straight from the foil to the water sample and
crush the tablet using a clean stirring rod.
4. Add the water sample to the 10 ml mark.
5. Close the vial tightly with the cap and swirl
gently several times until the tablet is
dissolved.
6. Place the vial correctly in the sample
chamber. See fig. 3.
7. Press the [Zero/Test] key.
Zero/Test
The method symbol flashes for approx.
CL 6
3 seconds.
"RESULT" appears in the display in mg/l total
RESULT
chlorine.
7.3.5 Combined chlorine
At first, determine and note down the values of total chlorine
(section 7.3.3 Total chlorine (free and combined
and free chlorine (section 7.3.2 Free
Calculation:
Combined chlorine = total chlorine - free chlorine
7.3.6 Tolerances
0-1 mg/l: ± 0.05 mg/l
> 1-2 mg/l: ± 0.10 mg/l
> 2-3 mg/l: ± 0.20 mg/l
> 3-4 mg/l: ± 0.30 mg/l
> 4-6 mg/l: ± 0.40 mg/l
chlorine.
6.7 Countdown/reaction period.
setting.
differentiated))
chlorine).