Chemistry Reference
In-Depth Information
mine Cu(II) and Cu(I) concentrations simultaneously in a mixture using
the following calibration equations obtained from the data shown in
Fig. 12.3 and Fig. 12.5:
I
=
k
C
+
2
k
C
[12.7]
()
( )
L,r
Cu I
Cu II
[
]
QC
=¢
+
C
[12.8]
()
()
p,o
Cu II
Cu I
with
I
L,r
the reductive limiting-current at -0.80 V vs. RE,
Q
p,o
the anodic
charge under the stripping peak; the constants (k and k¢) correspond to the
slopes of the curves shown in Fig. 12.3 and Fig. 12.5. This set of two equa-
tions contains two unknown parameters (Cu(II) and Cu(I) concentrations);
therefore it is possible to obtain these concentrations using the following
equations, derived from Equations 12.7 and 12.8:
-
k
QI
+
k
¢
p,o
L,r
C
()
=
[12.9]
Cu II
kk
¢
-+
¢
k
I
2
k
Q
L,r
p,o
C
()
=
[12.10]
Cu I
kk
It can be seen that, from measuring the limiting-current of the reduction
wave and the charge of the stripping peak, it is possible to obtain the Cu(I)
and Cu(II) concentrations simultaneously after calibration (determination
of k and k¢).
12.3
Determination of SO
2
reactions as a function
of pH and its detection at modified
carbon-fibre electrodes
12.3.1 Introduction
Sulphur dioxide is used in many applications such as organic synthesis
21
,in
lithium batteries
22
and as a preservative. Besides detection and monitoring
of sulphur dioxide in these and other applications, detection is also impor-
tant for environmental reasons
23
. Sulphur dioxide is a major atmospheric
pollutant and has a serious impact on buildings and vegetation as compo-
nent of acid rain
23
. Depending on the pH of the solution, sulphur dioxide
transforms into bisulphite and/or sulphite according to the following
reactions
24
:
k
1
Æ
(
)
SO
◊
x
H O
HSO
-
++-
H
+
x
1 H O
[12.11]
2
2
3
2
k
-
1
