18
In the case of an unknown duration of the signal peaks it is recommended to make a
chromatogram with time constant = 0 ms or = 10 ms and to choose a time constant
τ
τ
shorter than half of the narrowest amplitude.
Measurement by temperature equalisation
The temperature of a solution has an influence on its electrical conductivity. This
dependency is linear for most materials, as shown in Fig. 8, equation 1. For a few materials
e.g. natural water, a non-linear function in accordance with DIN 7888 is applicable. The
mikron 81 is fitted with a linear temperature equalisation device. Furthermore, the specific
temperature coefficient (in %/°C) of the material investigated, which can be looked up in
chemical tables, will be added to the chromatography programme.
σ
ϑ
100 +
c
ϑ
(
ϑ – ϑ
ref
)
σ
(
ϑ
ref
)
σ
(
ϑ
) =
Fig. 8: Linear temperature dependence of electrical conductivity
100
(
σ
(
ϑ
2
) –
σ
(
ϑ
ref
)
)
· 100
c
ϑ
(
ϑ
2
–
ϑ
ref
) ·
σ
(
ϑ
ref
)
(1)
(2)
electrical conductivity
temperature
S/m
°C
c
ϑ
ref
specific temperature coefficient
reference
%/°C
=
