English (GB)
28
7.15 Ozone, 0.02 - 2 mg/l O
3
7.15.1 Important notes
1. Vial cleaning:
As many household cleaners (e.g. dishwasher detergent)
contain reducing substances, the subsequent determination of
ozone 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. When preparing the sample, the escape of ozone gases,
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 tablet is added.
Use 0.5 mol/l sulphuric acid and 1 mol/l sodium hydroxide,
respectively.
4. Turbidity can lead to errors:
The use of the
DPD No. 1
tablet in samples with high calcium
ion content* and/or high conductivity* can lead to turbidity of
the sample and therefore incorrect measurements.
*) It is not possible to give exact values, because the
development of turbidity depends on the nature of the
sample.
5. For concentrations between 2 and 6 mg, the photometer
shows that the measuring range (Overrange) has been
exceeded. Concentrations above 6 mg/l ozone can lead to
results showing 0 mg/l. In this event, the water sample must
be diluted with water free of ozone. 10 ml of the diluted
sample should be mixed with the reagent and the
measurement repeated (plausibility test).
6. If
"???"
is displayed at a differentiated test result, see section
8.1 Operating messages in the display (error display)
.
7. All oxidising agents in the samples interfere as they react in
the same way as ozone.
7.15.2 In the presence of chlorine
The following selection is shown in the
display:
for the determination of ozone in the
presence of (with) chlorine.
for the determination of ozone in absence of
(without) chlorine.
Select the desired differentiation
(with/without chlorine) using the arrow keys
and .
Confirm with the
key.
3
0
0
Ozone
with Cl
without Cl
>> with Cl
>> without Cl
>>
1. Fill a clean vial (
∅
24) with 10 ml of the
water sample. Close tightly with the cap.
2. Place the vial in the sample chamber
correctly. See fig.
.
3. Press the [Zero] key.
4. Remove the vial from the sample
chamber and empty it, leaving a few
drops in the vial.
5. Add one
DPD No. 1
tablet
(No
) and one
DPD No. 3
tablet (No
) straight from the
foil and crush the tablets using a clean
stirring rod.
6. Add water sample to the 10 ml mark.
7. Close the vial tightly with the cap and
swirl gently several times until the tablets
are dissolved.
8. Place the vial in the sample chamber
correctly. See fig.
.
9. Press the [Test] key. Wait for a reaction
period of 2 minutes.
When the reaction period is finished, the
measurement starts automatically.
10. Remove the vial from the sample
chamber, empty the vial, rinse vial and
cap several times.
11. Add one
DPD No. 1
tablet
(No
) and one
DPD No. 3
tablet (No
) straight from the
foil and crush the tablets using a clean
stirring rod.
12. Fill a second clean vial with 10 ml of the
water sample.
13. Add one
Glycine
tablet (No
straight from the foil and crush the tablet
using a clean stirring rod.
14. Close the vial tightly with the cap and
swirl gently several times until the tablet
is dissolved.
15. Transfer the contents of the second vial
into the prepared vial.
16. Close the vial tightly with the cap and
swirl gently several times until the tablets
are dissolved.
17. Place the vial in the sample chamber
correctly. See fig.
.
18. Press the [Test] key. Wait for a reaction
period of 2 minutes.
After the reaction period is finished, the
measurement starts automatically.
The result is shown in the display in:
– mg/l ozone
– mg/l total chlorine
3
0
0
prepare Zero
press ZERO
Zero accepted
prepare T 1
press TEST
∅
24
Countdown
2:00
Countdown
2:00
T 1 accepted
prepare T 2
press TEST
*,** mg/l O3
*,** mg/l total Cl
Summary of Contents for DIT-M
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