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Indicator Electrodes, Potentiometry, Electrochemistry, Electrode Kinetics, Electrogravimetry, Polarography, Square Wave Voltammetry, Wavelength Selection, Types of Spectroscopy, Detectors, Theory of Molecular Absorption, Absorption by Organic Molecules, Applying UV-vis Spectroscopy are major topics of this course. Main points from these slides are: Membrane, Membrane Electrodes, Glass Membrane Electrode, Liquid Membrane Electrode, Solid State Membrane, Permeable Membrane, Combination Ph Electrod
Typology: Slides
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(^) ] = a+
(^1)
] = a+
2
solution 1
solution 2
across membranepotential develops
thin glass membrane
o
with AgClcoatedAg wire Filling solution0.1 M HCl seal connection^ Electrical
Thin glass membrane
nd step is to use any other pH buffer^
mV
pH
(^4)
7
without changing itline around isopotentialSlope/temp control pivots
Ag Cell for pH measurement (shorthand notation) (s) (^) AgCl
(s) (^) Cl
(aq)^ -
H unk+
HCl(0.1M) AgCl
(sat’d)
(^) Ag
(s)
reference electrode
test soln
glass electrode
solutions are the same activity,
potential should be 0 but it’s not
cell (^) = E
ind (^) – E
ref (^) + E
j +E a
raise pH) and Hconcentration is high (from NaOH used to
is very low. Electrode
responds slightly to Na
& gives a lower
most selective for Hthe electrode responds to many ions but isthe concept of selectivity coefficients wherereading than actual pH. This is related to
(^). Problem occurs+
because Na
is 10 orders of magnitude
higher than H
in the solution.
(^4) + , Rb
, Cs+
(^) , Li+
, Ag+
(cations only) by
varying glass composition
Cagroups selective forwith phosphateorganic compound– water immiscibleLiquid ion exchanger 2+ in a hydrophobic^
membrane
Ag/AgClCaCli.e., fixedsolutionFilling Ag wire 2
membrane(red) to wetexchangerexcess ionfilled withReservoir
Ion
exchanger
2+ electrode is the same as^
for glass electrode, however, since Ca
2+ is^
divalent n = 2
(^) Nernstian slope = 29.5 mV
per 10 fold change in concentration
2+ is approx. 10^
M^
2+ than for Mg^
2+
2+ than Na^
or K
Table of liquid membrane electrodes
Ag wire Solid State Membrane Electrodes
Ag/AgClresponds toelectrodecation that[Cl-] andwith fixedsolutionFilling Solid state membrane
(must be ionic conductor)
Pb 2+
Ag
(^2) S + PbS
Cd 2+
Ag (^2) S + CdS
Cu 2+
Ag (^2) S + CuS
Ag (^) , S+
2-
Ag (^2) S
Ag (^) , I+
AgI
Ag (^) , Br+
AgBr
Ag (^) , Cl+
AgCl
F , La-
3+
LaF
3
Ion Determined
MembraneSolid State Membrane Chemistry
Commercially Available Solid State Ion Selective Electrodes (ISEs)
mba = must be absent mr = maximum ratio of interferent to analyte
(^3) ) is the key component of electrode
(^4) + ] which
responds to changes in [NH
(^3) ] passing
membrane according to
NH
3
(^2) O
NH
(^4) +
