Ch.10 - Electrochemical Sensors Flashcards
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what are the most popular transducers for biosensors?
optical and electrochemical, followed by piezoelectric and thermal.
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What is an electrochemical sensor?
Electrochemical transducer where the concentrations of ions or chemicals are converted into electrical voltage (potentiometric), electrical current (amperometric), or electrical resistance/conductance (conductometric).
Devices that detect analytes by measuring electrical signals generated from chemical reactions.
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What is an electrochemical biosensor?
the combination o an electrochemical sensor and bioreceptors (enzymes or antibodies)
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how an electroltic cell works?
it decomposes ionic chemical compounds by applying voltage to its solution. Two electrodes are inserted into a solution o metal salts(electrolytes). The current flowing between the electrodes cause that the electrons were taken rom metal ions (ocidation, while the other electrode releases metal ions. look at 10.1
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What are the factors that alter the current flowing through the reaction
The current that flows between the electrodes
depends not only on the voltage that is applied, but also on the electrical properties
of the solution.
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What is a electrochemical cell?
It is a device that generetes electrical voltage and current.
How an electrochemical cell works?
Like electrolytic cell it has two electrodes inserted into electrolytes solutions. The main dierence is that they are separete by a salt bridge or a semipermeable membrane.
when the change in Gibbs free energi is negative
ΔG < 0 when the orward reaction is spontaneous.
How is the cahnge in Gibbs free energy equated?
ΔG =-nFΔE
n number of electrons
F Faraday constant = 96,487 C mol−1
ΔE electrical potential difference (V)
ΔG = RT ln K
R gas constant = 8.3145 J K−1 mol−1
T temperature (K)
K equilibrium constant
Define conductivity and resistivity.
Conductivity measures a material’s ability to conduct electric current, while resistivity is its opposition to electric current
Why do you need TL082 over LM741 in measuring pH?
TL082 has higher input impedance and lower bias current, essential for accurate pH measurements with glass electrodes
Define potentiometry.
Measuring the voltage of an electrochemical cell to determine ion concentrations.
What is an ion-selective electrode (ISE)?
An electrode that selectively measures the concentration of specific ions.
What are pH electrodes based on?
The Nernst equation, which relates electrode potential to hydrogen ion concentration.
How do amperometric biosensors work?
By measuring the current produced during the oxidation or reduction of a target analyte.
What is conductivity in electrochemical sensors?
A measure of a solution’s ability to conduct electricity, influenced by ion concentration.
What is the role of a reference electrode?
It provides a stable reference potential against which the working electrode’s potential is measured.
Why is a calomel electrode preferred?
It is stable, easy to use, and has a reproducible potential.
How is fluoride measured with an ISE?
By detecting potential changes proportional to fluoride ion concentration.
What is a redox reaction in electrochemical sensors?
A chemical reaction involving the transfer of electrons, producing measurable electrical signals.
What is the Nernst equation?
E=E_0 −(RT/n) lnQ, describing the electrode potential based on ion activity.
How is a pH meter circuit designed?
Using op-amps to amplify and linearize the pH-sensitive electrode signal.
What are electron mediators?
Molecules that facilitate electron transfer in electrochemical reactions.
How does buffer preparation affect pH measurements?
A: Proper buffers ensure stable pH for accurate measurements.
Q: What is the purpose of a conductivity sensor?
A: To measure the ionic content and conductivity of a solution.
Q: What factors affect sensor selectivity?
A: Electrode material, ionophore choice, and interference from other ions.
Q: Why are amperometric sensors used for glucose detection?
A: They offer high sensitivity by measuring currents proportional to glucose oxidation.
Q: How are enzymes used in electrochemical sensors?
A: Enzymes catalyze reactions that produce measurable electrical signals.
Q: What are the benefits of microfabricated electrochemical sensors?
A: Small size, cost efficiency, and suitability for point-of-care diagnostics.
Q: How do you calculate standard electrode potential (E°)
A: 𝐸°cell=𝐸°cathode−𝐸°anode
Q: Why is a calomel electrode preferred over a hydrogen electrode?
A: It is more stable and easier to use.
Q: Define conductivity and resistivity.
A: Conductivity measures current flow; resistivity is the opposition to flow.
Q: Why use TL082 over LM741 for pH measurements?
A: TL082 has lower input bias current and higher input impedance.
Q: How can a pH meter replace an op-amp circuit for fluoride detection?
A: It measures ion activity directly, with different calibration curves.
Q: How does an op-amp circuit generate pH-specific voltages?
A: It amplifies and offsets the electrode signal linearly based on pH.
