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Questions and Answers
Potentiometry is the measurement of an electrical current between two electrodes in a solution.
Potentiometry is the measurement of an electrical current between two electrodes in a solution.
False (B)
An Ion Selective Electrode consists of three electrodes: reference electrode, indicator electrode, and glass electrode.
An Ion Selective Electrode consists of three electrodes: reference electrode, indicator electrode, and glass electrode.
False (B)
An Ion Selective Electrode (ISE) is a transducer that converts the concentration of specific ions in a solution into electrical potential.
An Ion Selective Electrode (ISE) is a transducer that converts the concentration of specific ions in a solution into electrical potential.
False (B)
The potential difference between the two electrodes in an ISE depends on the concentration of the specific ion in the solution.
The potential difference between the two electrodes in an ISE depends on the concentration of the specific ion in the solution.
Glass membranes are only used for detecting multiple charged cations.
Glass membranes are only used for detecting multiple charged cations.
Crystaline membranes are made from a mixture of different substances.
Crystaline membranes are made from a mixture of different substances.
Ion exchange resin membranes are not commonly used in ISE.
Ion exchange resin membranes are not commonly used in ISE.
Enzyme membranes are not selective to specific ions.
Enzyme membranes are not selective to specific ions.
Ion exchange resin membrane is the least common type of ion selective electrode.
Ion exchange resin membrane is the least common type of ion selective electrode.
Enzyme membrane is a true electrode with a single reaction mechanism.
Enzyme membrane is a true electrode with a single reaction mechanism.
Ion selective electrodes are affected by sample color and turbidity.
Ion selective electrodes are affected by sample color and turbidity.
Direct ion selective electrodes require sample dilutions.
Direct ion selective electrodes require sample dilutions.
Ion selective electrodes are fragile and prone to blockage by proteins.
Ion selective electrodes are fragile and prone to blockage by proteins.
Ion selective electrodes can only measure positive ions.
Ion selective electrodes can only measure positive ions.
Study Notes
Ion Selective Electrode (ISE)
- Ion Selective Electrode (ISE) is a transducer or sensor that converts the activity of a specific ion dissolved in a solution into an electrical potential.
Potentiometry
- Potentiometry is the measurement of an electrical potential difference between two electrodes (reference electrode and indicator electrode) in an electrical solution.
- Uses of potentiometry:
- Analytical chemistry
- Electrolyte measurement
- Body fluids like plasma, serum, sweat analysis
- Biochemistry or biophysical research
Principle of ISE
- An ISE consists of two electrodes: a reference electrode and an indicator electrode.
- The indicator electrode develops a potential difference due to ion exchange between the sample and the inorganic membrane.
- The potential difference is measured against a stable reference electrode of constant potential.
- The potential difference depends on the activity of the specific ion in the solution.
Components of ISE
- Three main components of an ISE:
- Indicator electrode
- Reference electrode
- Ion selective membrane
Types of ISE
- Direct ISE: measures the sample without dilution
- Indirect ISE: measures the sample after dilution
Types of Ion Selective Membranes
- Four main types of ion selective membranes:
- Glass membrane
- Crystalline membrane
- Ion exchange resin membrane
- Enzyme membrane
Glass Membrane
- Made from ion exchange type of glass
- Advantage: good selectivity
- Disadvantage: only suitable for a few single-charged cations (e.g., H+, Na+, Ag+)
Crystalline Membrane
- Made from mono or polycrystalline of a single substance
- Advantage: good selectivity for both cations and anions (e.g., fluoride selective electrode)
Ion Exchange Resin Membrane
- Made from special polymers with ion exchange ability
- Most common type of ion selective electrode (e.g., potassium selective electrode)
Enzyme Membrane
- Not a true electrode, as it has a double reaction mechanism:
- First mechanism: reaction between enzyme and specific substance, producing OH- or H+
- Second mechanism: detection of OH- or H+ by ISE (e.g., glucose selective electrode)
Advantages of ISE
- Simple
- Easy to handle
- Measures both positive and negative ions
- Inexpensive
- Unaffected by sample color and turbidity
Disadvantages of ISE
- Electrode can be blocked by proteins
- Interference from other ions
- Electrodes are fragile
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Description
Test your knowledge of Ion Selective Electrodes, including definition, principle, components, types, and advantages and disadvantages. Also, learn about potentiometry and ion selective membranes.
