1. GROUP 7
ADVANCES IN ION SELECTIVE
ELECTRODES(ISE)
GROUP MEMBERS:
YAAKOB BIN ABD RAZAK (154631)
AMIR BIN HASANUDIN (154046)
ASILAH BTE JAMIL (154423)
NOR HIDAYAT BINTI YUSOF (152356)
INTAN NORYANA BINTI AHMAD (153741)
NORSYAMIMI BINTI CHE SULAMAN (153504)
NUR SHUHADA BINTI MOHD MOKHTARUDDIN (153142)
NURUL FADZILLAH BINTI MOHD HATTA (152266)
FAZURA EMYZA BINTI ABD AZIZ (153819)
NUR FATIHAH BINTI ABAS (154120)

2. Preview
1) Introduction to Ion Selective Electrodes,ISE
2) Composition of ISE(Glass Membrane Electrode,Solid State
Electrode,Liquid Membrane Electrode,Gas Sensing Electrode)
3) Parameters of ISE(sensitivity,selectivity,detection limit and
response time)
4) Potentionmetric measurements of ISE(in vivo, on line,on site)
5) The Recent advance(application of ISE)

3. Ion selective electrodes(ISE)
-An ion-selective electrode (ISE), also known as a specific ion
electrode (SIE), is a transducer (or sensor) that converts the activity of
a specific ion dissolved in a solution into an electrical potential, which
can be measured by a voltmeter or pH meter.
-Several types of sensing electrodes are commercially available which
are Glass Membrane Electrode, Solid State Electrode, Liquid
Membrane Electrode,Gas Sensing Electrode

4. • Ion Selective Electrodes (including the most common pH electrode) work on the
basic principal of the galvanic cell .By measuring the electric potential generated
across a membrane by "selected" ions, and comparing it to a reference
electrode, a net charge is determined. The strength of this charge is directly
proportional to the concentration of the selected ion. The basic formula is given for
the galvanic cell:
Ecell = EISE - ERef

5. TYPES OF ION SELECTIVE
ELECTRODE (ISE)
•Glass Membrane Electrode
•Solid State Electrode
•Liquid Membrane Electrode
•Gas Sensing Electrode

6. GLASS MEMBRANE ELECTRODE
• Glass electrode are responsive to univalent cations
( H+ , Na+)
• The selectivity for this cation by varying the composition
of a thin ion sensitive glass membrane.
• Example: pH electrode
- used for pH measurement
- used as a transducer in various gas and biocatalytic
sensor, involving proton generating or consuming
reaction.

7. pH electrode
•Glass membrane manufactured from SiO2 with negatively
charged oxygen atom.
•Inside the glass bulb, a dilute HCl solution and silver wire
coated with a layer of silver chloride.
•The electrode is immersed in the solution and pH is
measured.

8. SOLID STATE ELECTRODE
 Solid state electrode are selective primarily to
anions.
 It may be a homogenous membrane electrode or
heterogeneous membrane electrode.
 Homogenous membrane electrode: ion-selective
electrodes in which the membrane is a crystalline
material (AgI/Ag2S).

9.  Heterogeneous membrane electrode: ion-selective
electrodes prepared of an active substance, or mixture
of active substances (silicone rubber or PVC).
 Example: Fluoride ion selective electrode

10. LIQUID MEMBRANE ELECTRODE
 Liquid membrane is a type of ISE based on water-
immiscible liquid substances produced in a polymeric
membrane used for direct potentiometric
measurement.
 Used for direct measurement of several polyvalent
cations (Ca ion) as well as a certain anions.

11.  Example: Ion Exchanger Electrode
•The polymeric membrane made of PVC to separate the
test solution from its inner compartment.
•Contains standard solution of the target ion.
•The filling solution contains a chloride salt for establishing
the potential of the internal Ag/AgCl wire electrode.

12. GAS SENSING ELECTRODE
 Available for the measurement of ammonia, carbon
dioxide and nitrogen oxide.
 This type of electrode consist of permeable
membrane and an internal buffer solution.
 The pH of the buffer changes as the gas react with it.

13.  The change is detected by a combination pH sensor
within the housing.
 This type of electrode does not require an external
reference electrode.

14. Parameters of ISE
 Sensitivity
 Selectivity
 Detection Limit
 Response Time

15. Nikolsky-Eisenman equation,
Where
 RT.ln10/F-Sensitivity(S)
 kxy-selectivity coefficient
 ax-activity of the ion, X
 ay-activity of the interfering ion, Y
 zx-charge of the primary ion, X
 zy-charge on the interfering ion, Y
 The ‘constant’-E0

16. Selectivity
 An electrode used to measure primary ion X selectively
may also slightly responds to interference ion Y.
 Selectivity coefficient, kxy,is used in ISE to distinguish the
ion X from ion Y in the same solution.
 kxy is not constant and depends on several factors including
the concentration of both elements, the total ionic strength
of the solution, and the temperature.
 The value of kxy, is defined by the Nikolsky-Eisenman
equation:
 The smaller the value of kxy ,the greater is the electrode’s
preference for the primary ion, X.

17. Sensitivity
 Ability to detect primary ion at the lower concentration.
 Theoretical value of S=59mV,represents 100%
sensitivity.
 The value of S varies with kxy
 small value of kxy means that the electrode is more
sensitive to primary ion,X instead of interfering ion,Y.

18. Detection limit
 Defined by the intersection of the two extrapolated linear
parts of the ion-selective calibration curve.
 LOD ~ 10-5-10-6 M is measured for most ISE.
 Observed LOD is often governed by the presence of other
interfering ions or impurities.
 Metal buffers can be used to eliminate the effects which
lead to the contamination of very dilute solutions. May
reduce LOD to 10-10 M.

20. Response time
 From the time the ISE and a reference electrode are
dipped in the sample solution (or the time at which the
ion concentration in a solution in contact with ISE and a
reference electrode is changed ) to when the potential of
the cell becomes equal to its steady-state value within 1
[mV] or has reached 90% of the final value (in certain
cases also 63% or 95%).
 The response time usually increases with decreasing
determinand concentration

21. Time constant of Rate of the charge-
the measuring Determinand transfer reaction
instrument diffusion through the across the
hydrodynamic layer membrane/solution
interface, which
results in charging of
the electrical double
layer at this interface
Rate of the exchange
reaction between the Factors
determinand in the influence
membrane and an
interferent in the response
time Dissolution of the
analyte membrane-active
component in the
analyte
Establishment of the Interferent
diffusion potential diffusion in the
across the membrane membrane

22. ON-LINE, ON SITE AND IN VIVO
POTENTIOMETRIC MEASUREMENTS

23.  Meanings:
1) on-line : being in progress now.
2) on-site : taking place or located at the side.
3) in vivo : within a living organism.

24.  ISE have been widely used as detectors in high-speed automated flow
analyzers such as air-segmented or flow injection systems for the high-speed
determination of physiologically important cationic or anionic electrolytes in
body fluids.
Example of flow injection
determination of physiologically
potassium in serum.
 Several designs of low-volume potentiometric flow detectors
have been reported.
Flow-through
potentiometric cell design

25. Potentiometric microelectrodes are very suitable for in vivo real time
clinical monitoring of blood electrolytes, intracellular studies, in situ
environmental surveillance or industrial process control. For example
Simon’s group described the utility of a system for on-line measurement
of blood potassium ion concentration during an open-heart surgery.
Miniaturized catheter-type ISE sensors
such as implantable probe represent
the preferred approach for routine
clinical in vivo monitoring of blood
electrolyte.
Diamond's group developed an array of
miniaturized chloride, sodium, and
potassium ISEs for point-of-care
analysis of sweat in connection to non-
invasive diagnosis of cystic fibrosis.
Miniaturized catheter-type ISE sensor

26. Recent Advancement of Ion Selective
Electrode (ISE)

27. Agriculture and Fishery Pollution Control
-Soil and fertilizer for -pH of acid rain, soil, surface water
Nitrate, Ammonium, -Contamination of surface water
Potassium to optimize the use of and ground water with ammonium
fertilizer. and nitrate
-Dissolved Oxygen and pH in ponds -Contamination of waste water with
for Cyanide, Cadmium, Mercury and
fish breeding. Copper
Industrial Production
Food and Quality Control
-Salinity and pH of Boiler
feed
Worldwide -Nitrate and Nitrite in meat and
application vegetables
water
-Chloride, Sodium, Nitrate and
-Cyanide in plating baths
Nitrite in
-Process (specific ions)
baby food.
-Cadmium in fish
Medical Diagnosis and Hygiene Control
-Potassium in urine
-Contamination in various ions.

28. Advantages of Ion Selective Electrode
(ISE) Technique
 When compared to many other analytical techniques, Ion-
Selective Electrodes are relatively inexpensive and simple to
use and have an extremely wide range of applications and wide
concentration range.
 Under the most favourable conditions, when measuring ions in
relatively dilute aqueous solutions and where interfering ions are
not a problem, they can be used very rapidly and easily.
 They are particularly useful in applications where only an order
of magnitude concentration is required, or it is only necessary to
know that a particular ion is below a certain concentration level.

29.  They are invaluable for the continuous monitoring of changes in
concentration for example in potentiometric titrations or monitoring
the uptake of nutrients, or the consumption of reagents.
 They are particularly useful in biological/medical applications
because they measure the activity of the ion directly, rather than the
concentration.
 ISEs are one of the few techniques which can measure both
positive and negative ions.
 They are unaffected by sample colour or turbidity.
 ISEs can be used in aqueous solutions over a wide temperature
range. Crystal membranes can operate in the range 0 C to 80 C
and plastic membranes from 0 C to 50 C.

30. Surface Plasmon Resonance (SPR)
 Based on immunosensors for detection and monitoring of low-molecular-
weight analytes of biomedical, food and environmental fields.
 SPR is a surface sensitive optical technique for monitoring biomolecular
interactions occurring in very close vicinity of a transducer (gold)
surface, and that has given it a great potential for studying surface-confined
affinity interactions without rinsing out unreacted or excess reactants in
sample solutions.
 It allows real-time study of the binding interactions between a biomolecule
(antibody) immobilized on a transducer surface with its biospecific partner
(analyte) in solution without the need for labeling the biomolecules by
exploiting the interfacial refractive index changes associated with any
affinity binding interaction.
 In general, an SPR immunosensor is comprised of several important
components: a light source, a detector, a transduction surface (usually
gold-film), a prism, biomolecule (antibody or antigen) and a flow system.

31. • The transduction surface is usually a thin gold-film (50–100 nm) on a
glass slide optically coupled to a glass prism through a refractive index
matching oil. In addition to gold, several metals can be used including
silver, copper and aluminium. However, gold is highly preferred due to its
chemical stability and free electron behaviour.

32. Thank you for your attention