Tintometer Lovibond MD 200 Instrucciones página 31

Methods
GB
Notes:
1. The hydrogen peroxide is determined in the form of yellow/orange coloured peroxoti-
tanic acids in strongly acidic media. In connection with neutral to weakly alkaline (~pH
10) samples, the acid in the reagent is sufficient in order to produce a medium suitable
for measurement. In the case of strongly alkaline samples (pH > 10), the samples must
be acidified before measurement otherwise the results may be deficient. This is achieved
by diluting the sample with a 5% sulphuric acid solution, for example, at a ratio of 1:1.
In contrast to many other colour reactions, in connection with the presence of hydrogen
peroxide, discoloration with long-term stability is achieved that can still be measured after
24 h. Particles in the sample solution or turbidity distort the analysis and must be eliminated
by centrifuging or simply filtering the sample solution prior to performing the measure-
ment. Falsification of the measurement results should also be expected in connection with
coloured solutions.
2. Oxidising agents such as chlorine, bromine, chlorine dioxide and ozone do not distort the ana-
lysis. On the other hand, however, water discoloration does distort the analysis. In this case,
proceed as described in the following:
• Fill a clean vial (16 mm Ø) with 10 ml of the water sample and perform zero calibration
(see "Operation").
• Measure the sample solution without the addition of drops of reagent
• Then the same sample solution, measured with the addition of the reagent drops
(result A).
• Calculations: mg/l H
3. Attention: The reference reagent contains a 25% sulphuric acid solution. It is recommended
to wear appropriate protective clothing (protective goggles/gloves).
Reagent
H O -reagent
2 2
MD200_3 02/2014
O = result A – result B
2 2
Form of reagent/Quantity
Liquid reagent / 15 ml
(result B).
Order-No.
424991
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