Thermo Fisher Scientific Ion Selective Electrodes Copper - Manual (Page 14)

Instruction Manual Copper Electrode
14
5. Plot the milliliters of EDTA added against the mV
potential on standard coordinate graph paper. See
Figure 2. The point of greatest potential change is
the endpoint.
6. The cupric ion concentration from the unknown is
calculated as follows:
V
t
M
t
M
Cu
+2
=
_____
V
Cu
+2
where:
M
Cu
+2 = concentration of cupric ion
in the sample (moles/liter)
V
t
= volume of EDTA added at endpoint
M
t
= EDTA concentration (moles/liter)
V
Cu
+2 = volume of unknown sample (100 ml)
ELECTRODE CHARACTERISTICS
Reproducibility
Electrode measurements reproducible to
∀2% can be obtained if
the electrode is calibrated every hour. Factors such as
temperature fluctuations, drift, and noise limit reproducibility.
Reproducibility is independent of concentration within the
electrode's operating range.