Lovibond Tintometer MD 100 Manuel D'instructions page 4

• Dilution
A dilution of the sample may be necessary if the analyte exceeds the measuring range
of the method, or if you want to minimise the impact of errors by means of dilution.
So that the dilution is as exact as possible, it should be carried out as follows:
The desired amount of pipette sample is placed into a 100 ml volumetric flask using an
appropriate pipette or smaller volume with a piston-type pipette. Fill these up to the
mark with deionised water and mix well.
Take the sample volume from this diluted sample, as described in the analysis instruc-
tions, remove and conduct the analysis. The displayed result is then converted from the
EN
output volume:
Example for 100 ml volumetric flask:
Pipette sample volume / [ml]
• Filtration
Turbidity of the sample can be removed by filtration prior to analysis if the analyte is
itself easily soluble in water and does not adsorb particles or is bound to them. It is
important to ensure that the filter is sufficiently pre-rinsed with sample in order not to
falsify the analyte concentration of the sample when carrying out filtration.
If a turbid or particle-containing sample is closed up before or during the actual analysis
(for example, in the determination of total phosphorus or COD) this sample should not
be filtered before analysis since the particles could contain analytes and therefore influ-
ence the result. The same turbidity most disappears as a result of digestion.
Weak turbidity can be compensated in appropriate photometers to the extent that
the turbidity base is measured and included on a second wavelength in addition to
the colour to be measured.
• Homogenisation
With samples holding particles or with turbid samples, which are to be digested, pay
attention in order that sufficient homogenisation of the sample is achieved before and
during the removal of a subset. To do this, the maximum speed of agitation (more than
5000 revolutions per minute) is commonly used, as it both smashes particles at the
same time as providing a sufficiently uniform distribution.
4
Sample
1
2
5
10
25
50
Result to be multiplied by
100
50
20
10
4
2
EN Handbook of Methods