Ch.10 - Electrochemical Sensors

Question 1

171

what are the most popular transducers for biosensors?

Answer 1

optical and electrochemical, followed by piezoelectric and thermal.

Question 2

171

What is an electrochemical sensor?

Answer 2

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.

Question 3

171.

What is an electrochemical biosensor?

Answer 3

the combination o an electrochemical sensor and bioreceptors (enzymes or antibodies)

Question 4

171

how an electroltic cell works?

Answer 4

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

Question 5

171

What are the factors that alter the current flowing through the reaction

Answer 5

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.

Question 6

171.

What is a electrochemical cell?

Answer 6

It is a device that generetes electrical voltage and current.

Question 7

How an electrochemical cell works?

Answer 7

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.

Question 8

when the change in Gibbs free energi is negative

Answer 8

ΔG < 0 when the orward reaction is spontaneous.

Question 9

How is the cahnge in Gibbs free energy equated?

Answer 9

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

Question 10

Define conductivity and resistivity.

Answer 10

Conductivity measures a material’s ability to conduct electric current, while resistivity is its opposition to electric current​

Question 11

Why do you need TL082 over LM741 in measuring pH?

Answer 11

TL082 has higher input impedance and lower bias current, essential for accurate pH measurements with glass electrodes​

Question 12

Define potentiometry.

Answer 12

Measuring the voltage of an electrochemical cell to determine ion concentrations.

Question 13

What is an ion-selective electrode (ISE)?

Answer 13

An electrode that selectively measures the concentration of specific ions.

Question 14

What are pH electrodes based on?

Answer 14

The Nernst equation, which relates electrode potential to hydrogen ion concentration.

Question 15

How do amperometric biosensors work?

Answer 15

By measuring the current produced during the oxidation or reduction of a target analyte.

Question 16

What is conductivity in electrochemical sensors?

Answer 16

A measure of a solution’s ability to conduct electricity, influenced by ion concentration.

Question 17

What is the role of a reference electrode?

Answer 17

It provides a stable reference potential against which the working electrode’s potential is measured.

Question 18

Why is a calomel electrode preferred?

Answer 18

It is stable, easy to use, and has a reproducible potential.

Question 19

How is fluoride measured with an ISE?

Answer 19

By detecting potential changes proportional to fluoride ion concentration.

Question 20

What is a redox reaction in electrochemical sensors?

Answer 20

A chemical reaction involving the transfer of electrons, producing measurable electrical signals.

Question 21

What is the Nernst equation?

Answer 21

E=E_0 −(RT/n) lnQ, describing the electrode potential based on ion activity.

Question 22

How is a pH meter circuit designed?

Answer 22

Using op-amps to amplify and linearize the pH-sensitive electrode signal.

Question 23

What are electron mediators?

Answer 23

Molecules that facilitate electron transfer in electrochemical reactions.

Question 24

How does buffer preparation affect pH measurements?

Answer 24

A: Proper buffers ensure stable pH for accurate measurements.

Question 25

Q: What is the purpose of a conductivity sensor?

Answer 25

A: To measure the ionic content and conductivity of a solution.

Question 26

Q: What factors affect sensor selectivity?

Answer 26

A: Electrode material, ionophore choice, and interference from other ions.

Question 27

Q: Why are amperometric sensors used for glucose detection?

Answer 27

A: They offer high sensitivity by measuring currents proportional to glucose oxidation.

Question 28

Q: How are enzymes used in electrochemical sensors?

Answer 28

A: Enzymes catalyze reactions that produce measurable electrical signals.

Question 29

Q: What are the benefits of microfabricated electrochemical sensors?

Answer 29

A: Small size, cost efficiency, and suitability for point-of-care diagnostics.

Question 30

Q: How do you calculate standard electrode potential (E°)

Answer 30

A: 𝐸°cell=𝐸°cathode−𝐸°anode

Question 31

Q: Why is a calomel electrode preferred over a hydrogen electrode?

Answer 31

A: It is more stable and easier to use.

Question 32

Q: Define conductivity and resistivity.

Answer 32

A: Conductivity measures current flow; resistivity is the opposition to flow.

Question 33

Q: Why use TL082 over LM741 for pH measurements?

Answer 33

A: TL082 has lower input bias current and higher input impedance.

Question 34

Q: How can a pH meter replace an op-amp circuit for fluoride detection?

Answer 34

A: It measures ion activity directly, with different calibration curves.

Question 35

Q: How does an op-amp circuit generate pH-specific voltages?

Answer 35

A: It amplifies and offsets the electrode signal linearly based on pH.