-
ELECTROANALYSIS electro
te active
>
of electro ns Speaks OX / RED 7 Eceu flows Eceui Ecatn Eanoae IR
Exchange between ouerpo
-
=
when current : = - -
-
- tential
•
i = 0 =D Measure potential (equilibrium ) include Concentration
paar ization
•
i # 0 =D Measure current (no equilibrium) 50 Eceui Eceu.io
is more
negative than
:
> anode Oxidation reduction
:
cathode :
'
>
0hm s Law I = > Reference electrode =
non -
polarizable so potential different is
constant
"
iaot reductor ↳
[ B)
b ☒ no current through this electro de
01059-16 ↳ 1
>
E = É -
n
.
log Ä AA + ne
-
5 BB >
How ? → Potentiostat to Control current & potential
-
→
is reduction half 3 electro des :
current between 2; reference not → E- constant
poef Êd
reaction
,
no irclrop !
d%É
9 c-
"
V01 tammetry +
Amper omeery > reduction rate : =
kccox , e electro
race mooie
-
sur
y
d%f
Faraday
↳
>
j =/ 0
Potential is →
jrerg =
.
A. n . ft constant
constant
te ↳m ! →
>
Oxidatior :
current is ④ → e- from Solution cmz s .
cm
'
mm:#
reduction : current is ② →
e- to Solution irea =
Anfkccox . e
same for iox !
>
If I flows → 3 effects at electrode that inhibit electron '
I iox ired =
Ant (kacreaie -
Kc Cox )
exchange
= -
,
e
'
1 . Over potential =
voltage required to overcome actiuation the
moreanaeyte in Solution → Traction rate
→
Tarrant
energy
•
oxidation Faster at higner potential ; Reduction at Lower
"
to form product
•
:
actiuation energy must be over Corne "" " "" "
4" transport from and to electro de aetermines
☐ Mount of current
°
Voltage is made more → faster reaction (ga =p °
3 processes
negative for analyte transport :
limiting
' '
1
•
current =
plateau , reaction is complete .
Migration =
movement of
charge
a species in an
•
E,
because water electroulsis can interfereert nigner / Lower electric field driven by Coulomb Force
( U / (m ) from
-
Choice of material depends on DA of Reaction Electric field comes from ir drop
current
-
cations → -0 electrode | different in anauytecone
/
.
in bulk and electrode surface
2 .
Potential drop (IR drop ) =
because of Solution resistance the anions → ☒ electroae
Solution E is not constant
•
Eso , =
i .
Rsa -
Fcoulomb =
q
.
E
9 Îelectric
↳ IR drop de RSOI di charge field ( Ucm )
can be redllced bij or )
( (auombs
•
te Rsoi Preventel by ir drop I I
more
general high electro vyte Concentration
High Rsoi aaaing
-
or by by non
: : -
electrolyte conductiuity reactive electro lyte .
Non reactive ions
-
win
transport more → & → Fcouiombt
charge q
3 .
Concentration polarization
=
because CONC .
Oxidator is → So there is less
migration arive !
Constant at electro de suface (< CONC .
bulk Solution ,
the
electrode potential becomes more
negative
, ELECTROANALYSIS
2. Diffusion =
passive transport of molecules ,
takes place >
current only measured if ox + red take place at same tinne
because Concentration
> DE is smalt so with Couple happen
of a
gradient only redox
dit
fincient ""
-
from high > low Concentration entratio >
current is limited by # e- in Solution # e-
area
graaien ,
= 0kt Solution
f ¥1
,
Fick's law of diffusion Da A I licatn / lianoael
'
Veq
-
first → after
=
: -
dx
= =
before and
DCI in
'
diffusion on A, Ax Area 1- anodic Currents ④ Catholic Currents -0
-
rate ✗
=
;
=
depen Óant on
Concentration gradient gets > [ox] [red ]
-
overtime maximum titration
smaller i is measuredwnere = → at
halfway
" [ OX ] =
[ RED ]
-
• at Yzway
↳
(
'
0 diffusion stops
' -
When ,
÷
,
-
diffusion di stand ddiff = IDI vt" [
veq
= 0
> no reaox Couple so no current
in
i i
helpend
-
÷
bij Convention =
moving molecules in solution by >
: a .
Mechanical processies (Stirling ) u
vt
"
a b c
↳
makes transport more efficient a: anavyte + reageert electro active Î
We constant
b :
analiste reactive
\ Karl Fischer :
convection =
constant tnickness diffusion C:
reageert reactive
layer ( d )
.tt#it0A-
^
iiim =
.
(a titrant is electroactine
v
↳ smaller → current T
°
> half wave potential
-
Eyz =
E- -
Éreference
of
•
giues info about Identity anauyte
Amperometry
>
rotating disk electro de →
iiim
× [( Jburr
iiim target mijner Speed → d gets →
i
gets trigger
•
at smaller
>
titrations :
current is measured for endpoint
1. mono -
amperometry =
rotating Platinum electro de + reference electro de
(must be plateau)
-
potential aifference is constant in
limiting current
-
curves :
jij ] ✓ a:
b :
analyte
reageert
is
is
oxiaized
oxidized
vi.
b c:
analyte + are oxidized
a c
reageert
↳
if reduction current is Negative
:
2. bi -
amperometry =
2 of the same metal electrodes in a stirred System
Karl
•
Fischer water titration :
water necessary for reaction to
takes place
•
smak constant
potential difference
Ecatn Eanoae
•
no reference electrode → +
charge , dependirg on
Concentration of Speaks
ELECTROANALYSIS electro
te active
>
of electro ns Speaks OX / RED 7 Eceu flows Eceui Ecatn Eanoae IR
Exchange between ouerpo
-
=
when current : = - -
-
- tential
•
i = 0 =D Measure potential (equilibrium ) include Concentration
paar ization
•
i # 0 =D Measure current (no equilibrium) 50 Eceui Eceu.io
is more
negative than
:
> anode Oxidation reduction
:
cathode :
'
>
0hm s Law I = > Reference electrode =
non -
polarizable so potential different is
constant
"
iaot reductor ↳
[ B)
b ☒ no current through this electro de
01059-16 ↳ 1
>
E = É -
n
.
log Ä AA + ne
-
5 BB >
How ? → Potentiostat to Control current & potential
-
→
is reduction half 3 electro des :
current between 2; reference not → E- constant
poef Êd
reaction
,
no irclrop !
d%É
9 c-
"
V01 tammetry +
Amper omeery > reduction rate : =
kccox , e electro
race mooie
-
sur
y
d%f
Faraday
↳
>
j =/ 0
Potential is →
jrerg =
.
A. n . ft constant
constant
te ↳m ! →
>
Oxidatior :
current is ④ → e- from Solution cmz s .
cm
'
mm:#
reduction : current is ② →
e- to Solution irea =
Anfkccox . e
same for iox !
>
If I flows → 3 effects at electrode that inhibit electron '
I iox ired =
Ant (kacreaie -
Kc Cox )
exchange
= -
,
e
'
1 . Over potential =
voltage required to overcome actiuation the
moreanaeyte in Solution → Traction rate
→
Tarrant
energy
•
oxidation Faster at higner potential ; Reduction at Lower
"
to form product
•
:
actiuation energy must be over Corne "" " "" "
4" transport from and to electro de aetermines
☐ Mount of current
°
Voltage is made more → faster reaction (ga =p °
3 processes
negative for analyte transport :
limiting
' '
1
•
current =
plateau , reaction is complete .
Migration =
movement of
charge
a species in an
•
E,
because water electroulsis can interfereert nigner / Lower electric field driven by Coulomb Force
( U / (m ) from
-
Choice of material depends on DA of Reaction Electric field comes from ir drop
current
-
cations → -0 electrode | different in anauytecone
/
.
in bulk and electrode surface
2 .
Potential drop (IR drop ) =
because of Solution resistance the anions → ☒ electroae
Solution E is not constant
•
Eso , =
i .
Rsa -
Fcoulomb =
q
.
E
9 Îelectric
↳ IR drop de RSOI di charge field ( Ucm )
can be redllced bij or )
( (auombs
•
te Rsoi Preventel by ir drop I I
more
general high electro vyte Concentration
High Rsoi aaaing
-
or by by non
: : -
electrolyte conductiuity reactive electro lyte .
Non reactive ions
-
win
transport more → & → Fcouiombt
charge q
3 .
Concentration polarization
=
because CONC .
Oxidator is → So there is less
migration arive !
Constant at electro de suface (< CONC .
bulk Solution ,
the
electrode potential becomes more
negative
, ELECTROANALYSIS
2. Diffusion =
passive transport of molecules ,
takes place >
current only measured if ox + red take place at same tinne
because Concentration
> DE is smalt so with Couple happen
of a
gradient only redox
dit
fincient ""
-
from high > low Concentration entratio >
current is limited by # e- in Solution # e-
area
graaien ,
= 0kt Solution
f ¥1
,
Fick's law of diffusion Da A I licatn / lianoael
'
Veq
-
first → after
=
: -
dx
= =
before and
DCI in
'
diffusion on A, Ax Area 1- anodic Currents ④ Catholic Currents -0
-
rate ✗
=
;
=
depen Óant on
Concentration gradient gets > [ox] [red ]
-
overtime maximum titration
smaller i is measuredwnere = → at
halfway
" [ OX ] =
[ RED ]
-
• at Yzway
↳
(
'
0 diffusion stops
' -
When ,
÷
,
-
diffusion di stand ddiff = IDI vt" [
veq
= 0
> no reaox Couple so no current
in
i i
helpend
-
÷
bij Convention =
moving molecules in solution by >
: a .
Mechanical processies (Stirling ) u
vt
"
a b c
↳
makes transport more efficient a: anavyte + reageert electro active Î
We constant
b :
analiste reactive
\ Karl Fischer :
convection =
constant tnickness diffusion C:
reageert reactive
layer ( d )
.tt#it0A-
^
iiim =
.
(a titrant is electroactine
v
↳ smaller → current T
°
> half wave potential
-
Eyz =
E- -
Éreference
of
•
giues info about Identity anauyte
Amperometry
>
rotating disk electro de →
iiim
× [( Jburr
iiim target mijner Speed → d gets →
i
gets trigger
•
at smaller
>
titrations :
current is measured for endpoint
1. mono -
amperometry =
rotating Platinum electro de + reference electro de
(must be plateau)
-
potential aifference is constant in
limiting current
-
curves :
jij ] ✓ a:
b :
analyte
reageert
is
is
oxiaized
oxidized
vi.
b c:
analyte + are oxidized
a c
reageert
↳
if reduction current is Negative
:
2. bi -
amperometry =
2 of the same metal electrodes in a stirred System
Karl
•
Fischer water titration :
water necessary for reaction to
takes place
•
smak constant
potential difference
Ecatn Eanoae
•
no reference electrode → +
charge , dependirg on
Concentration of Speaks
