Metrohm tiamo 2.3 (process analysis) - Manual (Page 1122)

5.6 Commands ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
1106 ￭￭￭￭￭￭￭￭ tiamo 2.3 (for Process Analysis)
( )
B i
N
i
c c
z
U
E U + + = log ) 0 (
The Nernst constant U
N
represents the theoretical slope s of the calibra-
tion function, divided by the charge z of the measuring ion. With anions it
has a negative sign, with cations a positive one.
The influence of the interfering ions is indicated as blank value concentra-
tion c
B
. A significant blank value reduces the lower measuring range and
therefore causes a deterioration of the detection limit.
For the calibration, there are thus three unknown quantities to be calcula-
ted, namely E(0), s and c
B
. In order to unambiguously calculate all parame-
ters, at least three standard measurements are thus necessary. A higher
number of standards increases the reliability of the mathematical calcula-
tion of the calibration function.
tiamo determines the calibration data for the concentration measurement
as for the pH calibration depending on the number of the standard solu-
tions used.
￭ 1 point calibration
– s: the existing value is kept if available. Otherwise the theoretical
slope U
N
/ z is used.
–
– c
B
: is set equal to 0.
￭ 2 point calibration
–
–
– c
B
: is set equal to 0.