Lovibond Tintometer MD 100 Manuel D'instructions page 3

Sample
Sampling
The first step of the analysis is the extraction of the sample to be analysed. The accura-
cy of the subsequent analysis results depends predominantly on proper sampling. The
primary objective of sampling is that the part taken represents the state of the whole as
best as possible.
Also, the requirements for sampling and sample preparation depend on the analytes to
be tested.
So, enough water must have gone through the pipe, in the example of determining
chlorine from a pipe network, before the actual sample is removed. Strong swirling of
the sample is to be avoided, since otherwise there could be chlorine outgassing during
the sampling. In the case of a total phosphorus determination in waste water, however,
the actual analyte content is not negatively affected by turbulence during the sampling.
It is, on the contrary, even desirable because waste water commonly contains solids,
so that removing some to a quiet zone of a channel can lead to a reduced amount of
solids being removed, so that the sample no longer represents the general state in the
channel.
Also, it can make sense to refer to several partial samples and then to combine them
to increase the representativeness of the sample.
To carry out the analysis of comparison measurement to another (e.g. stationary)
measuring system, make sure that in both cases the actual same sample is measured,
so with both measurements there is no temporal or local difference in the sampling (e.g.
for comparative measurements, through a direct sampling of the installed measuring
system and not the channel from which the sample is taken – a permanently installed
measuring system).
Sample preparation
Before a sample is analysed, preparatory steps are usually necessary, which can have
a significant influence on the result.
• Stabilisation
For parameters measured directly on the site, the sample should be stabilised before
transport and storage so that the analyte remains unchanged.
Parameter
Cl , Br , ClO
2 2 2
Heavy metal
Heavy metal
COD
NH , NO , NO
4 3 2
handled
PO , P
4
• Neutralisation
Most analytical methods only work properly in a defined pH range. If the sample materi-
al prevents to be of a significantly different pH or has a very strong buffering capacity so
that the reagent can amend this target pH range, the user must amend the pH value of
the sample material accordingly.
EN Handbook of Methods
Handling
none, analyse immediately
not handled
to pH 1 with HNO
3
cool to 2° - 5°C
none, analyse immediately
short-term analysis
to pH 1 with HNO
3
Sample
Storage
not possible
short-term analysis
max. 4 weeks
max. 24 h
only in exceptional cases
at 2° - 5°C for max. 3hnot
max. 4 weeks
EN
3