Electrochemical methods of analysis are vital in pharmaceutical analysis, integrating redox reactions, electrode kinetics, and sensitive electroanalytical techniques to quantify drugs, impurities, and ions. Core methods include potentiometry, voltammetry (linear sweep, cyclic, differential pulse), amperometry, and coulometry, alongside ion-selective electrodes and modern electrochemical sensors and biosensors. These approaches provide high sensitivity, selectivity, low detection limits, rapid response, and utility in dissolution testing, stability studies, and quality control for B.Pharm students. Mastery of Nernstian behavior, electrode materials, cell design, signal interpretation, method validation, and sample preparation is essential for reliable assays. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which electrochemical technique measures potential of an indicator electrode against a reference electrode with no current flow?
- Potentiometry
- Amperometry
- Voltammetry
- Coulometry
Correct Answer: Potentiometry
Q2. The Nernst equation relates electrode potential to:
- Temperature and electrode surface area
- Concentration (activity) of redox species and temperature
- Scan rate and current
- Applied potential and resistance
Correct Answer: Concentration (activity) of redox species and temperature
Q3. In cyclic voltammetry, the peak current for a reversible diffusion-controlled redox process is proportional to:
- The square of the scan rate
- The inverse of scan rate
- The square root of scan rate
- Logarithm of scan rate
Correct Answer: The square root of scan rate
Q4. Which electrode serves as a common stable reference electrode in aqueous electrochemistry?
- Platinum electrode
- Glass electrode
- Silver/silver chloride (Ag/AgCl) electrode
- Gold electrode
Correct Answer: Silver/silver chloride (Ag/AgCl) electrode
Q5. Stripping voltammetry is especially useful for:
- Measuring pH of solutions
- Trace metal analysis at very low concentrations
- Determining electrode surface area
- Measuring conductivity
Correct Answer: Trace metal analysis at very low concentrations
Q6. Which parameter describes the smallest concentration reliably distinguished from a blank?
- Limit of quantitation (LOQ)
- Limit of detection (LOD)
- Calibration range
- Linearity coefficient
Correct Answer: Limit of detection (LOD)
Q7. In amperometric detection, the measured signal is:
- Potential at zero current
- Current at a fixed applied potential
- Resistance change over time
- Charge passed per mole
Correct Answer: Current at a fixed applied potential
Q8. Coulometry quantifies analyte by measuring:
- Potential difference at equilibrium
- Total charge passed during complete electrolysis
- Concentration by light absorption
- Electrical conductivity of the solution
Correct Answer: Total charge passed during complete electrolysis
Q9. An ion-selective electrode (ISE) responds primarily to:
- Redox-active molecules only
- Specific ionic activity in solution
- Temperature variations
- Electrode surface roughness
Correct Answer: Specific ionic activity in solution
Q10. Differential pulse voltammetry (DPV) is preferred over linear sweep for trace analysis because:
- It uses no supporting electrolyte
- It provides higher sensitivity and better resolution
- It is independent of diffusion control
- It eliminates the need for reference electrodes
Correct Answer: It provides higher sensitivity and better resolution
Q11. A common working electrode material offering wide potential window and low background current is:
- Glass carbon (glassy carbon)
- Silver
- Mercury drop
- Brass
Correct Answer: Glass carbon (glassy carbon)
Q12. In cyclic voltammetry, a peak separation (ΔEp) close to 59/n mV at 25°C indicates:
- A chemically irreversible process
- A reversible one-electron redox couple
- A diffusion-limited, multi-electron transfer
- Significant ohmic drop
Correct Answer: A reversible one-electron redox couple
Q13. Which law underpins the relationship between flux and concentration gradient in diffusion-controlled electrochemical processes?
- Faraday’s law
- Fick’s law
- Ohm’s law
- Beer-Lambert law
Correct Answer: Fick’s law
Q14. Faraday’s law relates the amount of substance transformed at an electrode to:
- Applied potential only
- Total charge passed (coulombs)
- Temperature of the solution
- Electrode surface area only
Correct Answer: Total charge passed (coulombs)
Q15. The primary advantage of using a supporting electrolyte in voltammetry is to:
- Increase solution viscosity
- Suppress migration and maintain ionic strength
- React with the analyte to form complexes
- Eliminate diffusion control
Correct Answer: Suppress migration and maintain ionic strength
Q16. Which electrode is typically used as the auxiliary (counter) electrode in three-electrode setups?
- Reference electrode
- Working electrode
- Inert conductor such as platinum or carbon
- Ion-selective electrode
Correct Answer: Inert conductor such as platinum or carbon
Q17. In potentiometric titration for pharmaceutical assay, the endpoint is detected by monitoring:
- Current transient at fixed potential
- Change in cell potential of the indicator electrode
- Total charge passed during titration
- Absorbance at specific wavelength
Correct Answer: Change in cell potential of the indicator electrode
Q18. Which statement about cyclic voltammetry reversibility is true?
- Reversible systems show peak current independent of concentration
- Reversible systems have symmetric anodic and cathodic peak shapes with predictable ΔEp
- Reversible systems only occur for adsorption-controlled processes
- Reversibility cannot be inferred from CV
Correct Answer: Reversible systems have symmetric anodic and cathodic peak shapes with predictable ΔEp
Q19. Which interference is a particular concern for ion-selective electrodes affecting selectivity?
- Electrode polishing artifacts
- Interfering ions with similar size/charge producing nonzero selectivity coefficients
- Temperature drift only
- Light sensitivity
Correct Answer: Interfering ions with similar size/charge producing nonzero selectivity coefficients
Q20. Adsorption of analyte on the electrode surface typically causes:
- Peak currents proportional to square root of scan rate
- Peak currents proportional to scan rate (linear dependence)
- No signal in voltammetry
- Only background noise
Correct Answer: Peak currents proportional to scan rate (linear dependence)
Q21. Which electrochemical sensor couples a biological recognition element with an electrode transducer for specific analyte detection?
- Ion-selective electrode
- Biosensor (e.g., enzyme electrode)
- pH electrode
- Conductometric titrator
Correct Answer: Biosensor (e.g., enzyme electrode)
Q22. In differential pulse voltammetry, pulses are superimposed on a linear potential sweep to:
- Decrease signal-to-noise ratio
- Enhance faradaic current relative to capacitive background
- Eliminate diffusion effects entirely
- Stabilize temperature
Correct Answer: Enhance faradaic current relative to capacitive background
Q23. The Randles–Sevcik equation relates peak current to which of the following?
- Concentration, diffusion coefficient, scan rate, and electrode area for reversible systems
- Only the applied potential and current
- Temperature and pH exclusively
- Electrode polishing time
Correct Answer: Concentration, diffusion coefficient, scan rate, and electrode area for reversible systems
Q24. Which technique directly oxidizes or reduces the entire analyte to determine amount based on total charge?
- Cyclic voltammetry
- Coulometry (bulk electrolysis)
- Potentiometry
- Conductometry
Correct Answer: Coulometry (bulk electrolysis)
Q25. Reference electrode junction potential arises due to:
- Mixing of electrolytes with different mobilities at the salt bridge interface
- Electrode surface roughness only
- Light causing photochemical reactions
- Magnetic fields near the cell
Correct Answer: Mixing of electrolytes with different mobilities at the salt bridge interface
Q26. Which modification improves selectivity and sensitivity of an electrode for a target drug molecule?
- Increasing electrode diameter only
- Surface modification with selective films or molecularly imprinted polymers
- Removing supporting electrolyte
- Using a less stable reference electrode
Correct Answer: Surface modification with selective films or molecularly imprinted polymers
Q27. Standard addition method in electroanalysis is used primarily to:
- Correct for matrix effects and sample interferences
- Reduce instrumental noise
- Increase scan rate effects
- Eliminate the need for calibration standards
Correct Answer: Correct for matrix effects and sample interferences
Q28. Which of the following is a disadvantage of mercury electrodes historically used in voltammetry?
- Very low overpotential for hydrogen evolution
- High toxicity and environmental concerns
- Limited negative potential window
- Poor reproducibility of surface renewal
Correct Answer: High toxicity and environmental concerns
Q29. In an amperometric biosensor for glucose, the enzyme glucose oxidase catalyzes reaction producing H2O2 which is detected by:
- Measuring change in conductivity
- Oxidation or reduction of H2O2 at a fixed potential producing current
- Measuring potential without current flow
- Colorimetric change only
Correct Answer: Oxidation or reduction of H2O2 at a fixed potential producing current
Q30. A major validation parameter for electrochemical methods in pharmaceutical QC ensuring reproducible response at different concentrations is:
- Signal latency
- Linearity and range
- Instrument weight
- Electrode color
Correct Answer: Linearity and range
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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