Paper electrophoresis MCQs With Answer

Paper electrophoresis MCQs With Answer offers a focused, exam-ready review for M. Pharm students studying Modern Pharmaceutical Analytical Techniques. This classic separation method uses an electric field to resolve charged analytes on buffer-saturated cellulose paper, and understanding its variables—pH, ionic strength, field strength, electroosmosis, and staining—builds strong analytical reasoning. The following MCQs go beyond recall, aiming to strengthen conceptual clarity on principles, instrumentation, optimization, artifact control, and pharmaceutical applications such as amino acid, peptide, alkaloid, and ion analysis. Each question includes a concise answer to support quick revision. Use these to diagnose weak areas, refine problem-solving, and connect theoretical fundamentals with practical method development and validation.

Q1. Which statement best describes the principle of paper electrophoresis?

• Separation based on differential adsorption on a stationary phase under solvent flow
• Separation based on differential migration of charged species on buffer-saturated paper under an electric field
• Separation based on molecular sieving through a crosslinked gel matrix
• Separation based solely on capillary action and partitioning

Correct Answer: Separation based on differential migration of charged species on buffer-saturated paper under an electric field

Q2. The most commonly used support for paper electrophoresis is:

• Cellulose acetate film
• Whatman 3MM chromatography paper
• Polyacrylamide slab
• Agarose gel slab

Correct Answer: Whatman 3MM chromatography paper

Q3. An amphoteric molecule with isoelectric point (pI) 7.4 is run at pH 9.0. Its net migration will be toward:

• The anode, as it carries a net negative charge above its pI
• The cathode, as it carries a net positive charge above its pI
• No migration at all
• Both electrodes equally due to zwitterionic balance

Correct Answer: The anode, as it carries a net negative charge above its pI

Q4. A typical field strength used in conventional paper electrophoresis is:

• 0.5–1 V/cm
• 5–20 V/cm
• 200–500 V/cm
• 1000–2000 V/cm

Correct Answer: 5–20 V/cm

Q5. Which change will most likely increase Joule heating and risk of band distortion during a constant-voltage run?

• Decreasing ionic strength of the buffer
• Lowering the applied voltage
• Increasing ionic strength of the buffer
• Using a thinner paper support

Correct Answer: Increasing ionic strength of the buffer

Q6. On cellulose paper, the electroosmotic (endosmotic) flow of buffer generally moves:

• Toward the anode due to positive fixed charges
• Toward the cathode due to negatively charged cellulose
• Equally in both directions, canceling out
• Randomly, independent of pH

Correct Answer: Toward the cathode due to negatively charged cellulose

Q7. The most specific post-run visualization reagent for amino acids on paper is:

• Ninhydrin
• Coomassie Brilliant Blue
• Iodine vapor
• Silver nitrate

Correct Answer: Ninhydrin

Q8. A suitable detection approach for nucleotides separated by paper electrophoresis is:

• UV densitometry at 260 nm
• Ninhydrin spray followed by heating
• Sudan III staining
• Amido Black staining

Correct Answer: UV densitometry at 260 nm

Q9. To minimize band broadening at the origin, the best practice for sample application is:

• Apply a large volume to ensure visibility
• Apply multiple spots over a wide area
• Apply a small, concentrated band using a microcapillary or microsyringe
• Mix the sample with dye and spread with a glass rod

Correct Answer: Apply a small, concentrated band using a microcapillary or microsyringe

Q10. Which strategy most effectively reduces electroosmotic flow on cellulose paper?

• Increase buffer pH to ionize cellulose
• Lower buffer pH to reduce surface charge on cellulose
• Switch to a higher ionic strength buffer
• Use a stronger organic modifier (e.g., 50% methanol)

Correct Answer: Lower buffer pH to reduce surface charge on cellulose

Q11. Two-dimensional paper electrophoresis is typically performed by:

• Running twice in the same direction using the same buffer
• Rotating the paper 90°, changing the pH/buffer, and running the second dimension
• Increasing voltage mid-run without changing orientation
• Using paper in the first dimension and gel in the second

Correct Answer: Rotating the paper 90°, changing the pH/buffer, and running the second dimension

Q12. Regarding power control, which statement is most accurate for paper electrophoresis?

• Constant current ensures constant field strength as resistance changes
• Constant voltage maintains field strength but current (and heating) can rise as resistance drops
• Constant power is routinely used to avoid heating
• Voltage mode is avoided due to unstable fields

Correct Answer: Constant voltage maintains field strength but current (and heating) can rise as resistance drops

Q13. Electrophoretic mobility (μ) of a molecule in paper electrophoresis is primarily determined by:

• Molecular weight alone
• Net charge-to-friction ratio (q/f) and buffer viscosity
• Paper thickness only
• Color of the molecule

Correct Answer: Net charge-to-friction ratio (q/f) and buffer viscosity

Q14. A basic drug with pKa 9.0 is analyzed at buffer pH 6.0. Its expected migration will be toward:

• The anode, as it is deprotonated
• The cathode, as it is protonated (cationic)
• Neither electrode, as it is at its pI
• Both electrodes due to amphoteric behavior

Correct Answer: The cathode, as it is protonated (cationic)

Q15. The main benefit of high-voltage paper electrophoresis (HVPE) with cooling is:

• Elimination of electroosmotic flow
• Faster separations with maintained resolution due to heat dissipation
• Ability to separate uncharged analytes
• No need for buffer reservoirs

Correct Answer: Faster separations with maintained resolution due to heat dissipation

Q16. Curved or distorted bands near the edges of the paper are most commonly caused by:

• Uniform field distribution
• Edge effect due to uneven wetting/drying and field non-uniformity
• Complete elimination of electroosmosis
• Use of narrow paper strips

Correct Answer: Edge effect due to uneven wetting/drying and field non-uniformity

Q17. To improve resolution between two weak acids with similar mobilities, the most effective first step is to:

• Increase sample volume substantially
• Fine-tune buffer pH to accentuate differences in degree of ionization
• Increase ionic strength to raise current
• Shorten the run time

Correct Answer: Fine-tune buffer pH to accentuate differences in degree of ionization

Q18. pH drift from electrode reactions (H+ at anode, OH− at cathode) is best minimized by:

• Using no buffer and only pure water
• Placing the paper directly into electrode solutions
• Using large buffer reservoirs and salt bridges to isolate electrode products from the paper
• Running at the highest possible voltage

Correct Answer: Using large buffer reservoirs and salt bridges to isolate electrode products from the paper

Q19. A reliable method for quantifying separated zones on paper electrophoresis strips is:

• Visual inspection and manual estimation
• Densitometric scanning of stained zones at appropriate wavelengths
• Measuring paper weight change
• Counting the number of bands only

Correct Answer: Densitometric scanning of stained zones at appropriate wavelengths

Q20. Which is a key limitation of paper electrophoresis relative to modern gel or capillary methods?

• Lower cost and simpler setup
• Lower resolution and greater band broadening for macromolecules
• Ease of sample recovery by elution
• Compatibility with a wide pH range

Correct Answer: Lower resolution and greater band broadening for macromolecules

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