Modes of capillary electrophoresis MCQs With Answer

Introduction: Modes of capillary electrophoresis MCQs With Answer is designed for M.Pharm students to strengthen understanding of various capillary electrophoresis (CE) modes used in pharmaceutical analysis. This collection focuses on principles, practical aspects, instrumentation issues and advanced variants such as CZE, MEKC, CGE, cIEF, ITP and CEC. Questions probe separation mechanisms, sample injection, electroosmotic flow control, preconcentration strategies, and troubleshooting (Joule heating, buffer selection, capillary coatings). Each MCQ includes plausible alternatives and clear answers to help students prepare for exams and laboratory application. The set emphasizes conceptual depth, method selection criteria and interpretation of CE results in drug analysis contexts.

Q1. What is the primary separation mechanism in capillary zone electrophoresis (CZE)?

• Partitioning between micelles and aqueous phase
• Size sieving through a gel matrix
• Differences in electrophoretic mobility of analytes
• Formation of focused pH zones at isoelectric points

Correct Answer: Differences in electrophoretic mobility of analytes

Q2. Which mode of CE is most appropriate for separating neutral compounds?

• Capillary gel electrophoresis (CGE)
• Micellar electrokinetic chromatography (MEKC)
• Capillary isoelectric focusing (cIEF)
• Isotachophoresis (ITP)

Correct Answer: Micellar electrokinetic chromatography (MEKC)

Q3. In capillary isoelectric focusing (cIEF), analytes are separated primarily by:

• Electrophoretic mobility differences at constant pH
• Partitioning into surfactant micelles
• Their isoelectric points within a pH gradient
• Size-dependent sieving in a polymer gel

Correct Answer: Their isoelectric points within a pH gradient

Q4. Which CE mode uses a discontinuous electrolyte system with leading and terminating ions to concentrate analytes?

• Capillary electrochromatography (CEC)
• Isotachophoresis (ITP)
• Capillary zone electrophoresis (CZE)
• Micellar electrokinetic chromatography (MEKC)

Correct Answer: Isotachophoresis (ITP)

Q5. Capillary gel electrophoresis (CGE) is most commonly used for:

• High-resolution separation of small neutral molecules
• Separation of proteins or nucleic acids by size
• Quantitative analysis of enantiomers
• Focusing peptides based on pI

Correct Answer: Separation of proteins or nucleic acids by size

Q6. Which technique combines chromatographic retention mechanisms with electroosmotic flow to separate analytes?

• Capillary zone electrophoresis (CZE)
• Capillary electrochromatography (CEC)
• Capillary isoelectric focusing (cIEF)
• Isotachophoresis (ITP)

Correct Answer: Capillary electrochromatography (CEC)

Q7. In MEKC, the role of micelles is to:

• Create a pH gradient for focusing
• Act as a pseudo-stationary phase for differential partitioning of neutral and charged analytes
• Form a molecular sieve for size exclusion
• Generate leading ions for isotachophoresis

Correct Answer: Act as a pseudo-stationary phase for differential partitioning of neutral and charged analytes

Q8. Which CE mode would be best for separating isoforms of a protein differing only slightly in charge?

• Micellar electrokinetic chromatography (MEKC)
• Capillary gel electrophoresis (CGE)
• Capillary isoelectric focusing (cIEF)
• Capillary electrochromatography (CEC)

Correct Answer: Capillary isoelectric focusing (cIEF)

Q9. Transient isotachophoresis (tITP) is used in CE primarily to:

• Separate proteins by isoelectric point
• Provide on-line sample stacking and preconcentration prior to zone separation
• Replace EOF with pressure-driven flow
• Generate micelle phases for neutral analytes

Correct Answer: Provide on-line sample stacking and preconcentration prior to zone separation

Q10. Which factor most directly controls electroosmotic flow (EOF) in an uncoated fused-silica capillary?

• Viscosity of the mobile phase only
• Surface charge of the capillary wall (silanol deprotonation) and buffer pH
• Presence of micelles in buffer
• Applied voltage polarity alone

Correct Answer: Surface charge of the capillary wall (silanol deprotonation) and buffer pH

Q11. Which mode of CE is most suitable for high-throughput DNA sizing and sequencing?

• Capillary isoelectric focusing (cIEF)
• Capillary gel electrophoresis (CGE)
• Micellar electrokinetic chromatography (MEKC)
• Isotachophoresis (ITP)

Correct Answer: Capillary gel electrophoresis (CGE)

Q12. A common approach to suppress EOF and reduce adsorption of basic drugs to the capillary wall is to:

• Increase buffer ionic strength without coating
• Apply higher voltage to overcome adsorption
• Use dynamic or permanent capillary coatings
• Use micelle-forming surfactants only

Correct Answer: Use dynamic or permanent capillary coatings

Q13. Which CE mode exploits differences in mobility but also uses a sieving polymer to separate by size—often applied to oligonucleotides?

• Capillary zone electrophoresis (CZE)
• Capillary gel electrophoresis (CGE)
• Micellar electrokinetic chromatography (MEKC)
• Capillary isoelectric focusing (cIEF)

Correct Answer: Capillary gel electrophoresis (CGE)

Q14. Non-aqueous capillary electrophoresis (NACE) is advantageous mainly because it:

• Increases EOF by raising pH
• Improves solubility and separation of hydrophobic pharmaceuticals
• Creates a gel matrix inside the capillary
• Focuses proteins at their pI

Correct Answer: Improves solubility and separation of hydrophobic pharmaceuticals

Q15. Which on-line preconcentration method in CE relies on creating a conductivity difference between sample zone and background electrolyte?

• Micellar sweeping
• Field-amplified sample stacking (FASS)
• Capillary electrochromatography
• Isoelectric focusing

Correct Answer: Field-amplified sample stacking (FASS)

Q16. In affinity capillary electrophoresis (ACE), selectivity is enhanced by:

• Using a strong sieving polymer
• Including a selective ligand or receptor in the buffer or on the capillary wall
• Operating at very high temperatures to denature complexes
• Adding micelles to form a pseudo-stationary phase

Correct Answer: Including a selective ligand or receptor in the buffer or on the capillary wall

Q17. Which issue is most directly caused by excessive Joule heating in high-voltage CE separations?

• Improved resolution due to higher diffusion
• Band broadening and loss of efficiency due to temperature gradients
• Generation of micelles from buffer salts
• Invariant EOF irrespective of buffer composition

Correct Answer: Band broadening and loss of efficiency due to temperature gradients

Q18. Capillary electrochromatography (CEC) offers higher efficiency than HPLC primarily because:

• It uses pressure-driven flow similar to HPLC
• Mass transfer is dominated by electroosmotic plug flow reducing longitudinal diffusion
• It eliminates the need for a stationary phase
• It operates exclusively with non-aqueous solvents

Correct Answer: Mass transfer is dominated by electroosmotic plug flow reducing longitudinal diffusion

Q19. Which CE mode is particularly useful for analyzing amphoteric small-molecule drugs with multiple ionizable groups?

• Micellar electrokinetic chromatography (MEKC)
• Capillary isoelectric focusing (cIEF)
• Capillary gel electrophoresis (CGE)
• Isotachophoresis (ITP)

Correct Answer: Capillary isoelectric focusing (cIEF)

Q20. Sweeping is an on-line concentration technique in MEKC that works by:

• Applying a pH gradient to focus analytes
• Using micelles to sweep analytes from the aqueous plug into the micellar phase during migration
• Generating a leading ion to stack analytes at a boundary
• Filling the capillary with a gel to trap analytes

Correct Answer: Using micelles to sweep analytes from the aqueous plug into the micellar phase during migration

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