Advantages, disadvantages and pharmaceutical applications of TLC MCQs With Answer

Introduction: Thin Layer Chromatography (TLC) is a rapid, cost-effective analytical tool widely used in pharmaceutical analysis for qualitative screening, impurity profiling, assay development, and monitoring reaction progress. B.Pharm students should master TLC concepts such as stationary phase, mobile phase selection, Rf value interpretation, visualization techniques, and densitometry quantification. Understand advantages like simplicity, low solvent use, and fast screening, as well as disadvantages such as limited sensitivity, reproducibility issues, and scaling constraints. Knowledge of HPTLC, sample preparation, derivatization, and validation enhances practical application in formulation development and quality control. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What does the Rf value in TLC represent?

• Ratio of substance spot height to plate height
• Distance traveled by solute divided by distance traveled by solvent front
• Retention time of analyte in minutes
• Relative fluorescence of a compound under UV light

Correct Answer: Distance traveled by solute divided by distance traveled by solvent front

Q2. Which stationary phase is most commonly used in classical TLC for pharmaceutical analysis?

• Silica gel
• Cellulose acetate
• C18-bonded silica
• Polystyrene

Correct Answer: Silica gel

Q3. Which mobile phase property most strongly affects compound migration in TLC?

• Viscosity only
• Polarity of the solvent system
• Color of the solvent
• Sample pH after spotting

Correct Answer: Polarity of the solvent system

Q4. Which visualization technique is suitable for non-UV active compounds on TLC?

• UV lamp at 254 nm
• Spray derivatization with anisaldehyde or ninhydrin
• Direct densitometry without reagent
• Using fluorescence quenching on 366 nm

Correct Answer: Spray derivatization with anisaldehyde or ninhydrin

Q5. HPTLC differs from classical TLC primarily by:

• Use of paper as stationary phase
• Smaller particle size and higher resolution plates
• Replacing mobile phase with gas
• Eliminating visualization steps

Correct Answer: Smaller particle size and higher resolution plates

Q6. One major disadvantage of TLC for quantitation is:

• Excessive solvent consumption compared to HPLC
• Low sensitivity and limited dynamic range compared to HPLC
• Impossible to separate polar compounds
• Requires radioisotopes for detection

Correct Answer: Low sensitivity and limited dynamic range compared to HPLC

Q7. What role does plate activation (heating at 100–120°C) serve before using silica TLC plates?

• Removes adsorbed moisture and improves reproducibility
• Introduces fluorescent indicator into the silica
• Coats the plate with a mobile phase
• Changes stationary phase polarity permanently

Correct Answer: Removes adsorbed moisture and improves reproducibility

Q8. In reversed-phase TLC, which stationary phase is used?

• Plain cellulose
• Silica gel impregnated with C18 or other nonpolar groups
• Activated alumina
• Ion exchange resin

Correct Answer: Silica gel impregnated with C18 or other nonpolar groups

Q9. Which parameter is critical when selecting a mobile phase for resolving two close spots?

• Solvent boiling point
• Incremental change in polarity or solvent ratio
• Color of solvent
• Spotting solvent viscosity only

Correct Answer: Incremental change in polarity or solvent ratio

Q10. Densitometry in TLC is used to:

• Measure the plate thickness
• Quantify spot concentration by measuring optical density
• Stain non-chromophoric spots
• Increase plate resolution by heating

Correct Answer: Quantify spot concentration by measuring optical density

Q11. A stability-indicating TLC method is designed to:

• Detect only the parent drug and ignore degradation products
• Separate and detect both drug and its degradation products
• Quantify the drug using mass spectrometry only
• Determine tablet hardness

Correct Answer: Separate and detect both drug and its degradation products

Q12. Which of the following is a green chemistry consideration in TLC?

• Using chlorinated solvents exclusively
• Minimizing solvent volume and choosing less toxic solvents
• Discarding plates after single use only
• Heating plates at extremely high temperatures

Correct Answer: Minimizing solvent volume and choosing less toxic solvents

Q13. Ion-pairing in TLC helps to:

• Increase volatility of analytes
• Improve retention and separation of ionic analytes
• Make nonpolar compounds polar
• Reduce detection sensitivity

Correct Answer: Improve retention and separation of ionic analytes

Q14. Which factor can cause poor reproducibility between TLC runs?

• Consistent spotting volume
• Fluctuations in humidity and plate conditioning
• Using the same mobile phase composition
• Identical development distance

Correct Answer: Fluctuations in humidity and plate conditioning

Q15. Preparative TLC is primarily used to:

• Analyze trace impurities quantitatively
• Isolate and recover milligram to gram amounts of purified compounds
• Improve the Rf values of analytical spots
• Measure the pH of samples

Correct Answer: Isolate and recover milligram to gram amounts of purified compounds

Q16. Which visualization reagent is commonly used for amino acids on TLC?

• Dragendorff’s reagent
• Ninhydrin
• Potassium permanganate
• UV 254 nm only

Correct Answer: Ninhydrin

Q17. Which statement about co-chromatography on TLC is correct?

• Co-chromatography is used to change stationary phase polarity
• It involves running a known standard with the sample to confirm identity
• It removes the need for visualization
• It always increases Rf values

Correct Answer: It involves running a known standard with the sample to confirm identity

Q18. Which of the following improves spot sharpening on a TLC plate?

• Overloading the sample spot
• Using narrower application bands and smaller sample volume
• Using highly viscous mobile phases
• Allowing solvent front to evaporate rapidly during development

Correct Answer: Using narrower application bands and smaller sample volume

Q19. For basic drugs, choosing an acidic mobile phase will typically:

• Convert the drug to its ionized form and reduce Rf on normal-phase silica
• Make the drug more nonpolar and increase Rf
• Have no effect on migration
• Destroy the stationary phase

Correct Answer: Convert the drug to its ionized form and reduce Rf on normal-phase silica

Q20. Which detector is commonly integrated in HPTLC densitometers for quantitative analysis?

• Mass spectrometer detector only
• UV-Visible photometric detector
• Flame ionization detector
• Atomic absorption detector

Correct Answer: UV-Visible photometric detector

Q21. Why is silica gel often fluorescence-activated (F254) in TLC plates?

• To make plates reusable multiple times
• To allow visualization of quenching spots under 254 nm UV
• To chemically react with analytes
• To increase plate thickness

Correct Answer: To allow visualization of quenching spots under 254 nm UV

Q22. During TLC development, a solvent front that moves too fast may cause:

• Better separation of closely eluting spots
• Poor resolution and tailing of spots
• Increased sensitivity in densitometry
• Permanent plate activation

Correct Answer: Poor resolution and tailing of spots

Q23. Which parameter is calculated to evaluate TLC method precision in quantitative work?

• Retention time deviation
• Relative standard deviation (RSD) of peak area or spot density
• Spot color intensity only
• Molar absorptivity of solvent

Correct Answer: Relative standard deviation (RSD) of peak area or spot density

Q24. Which of the following is an advantage of TLC in pharmaceutical QC labs?

• High throughput screening with minimal equipment and fast turnaround
• Automated identification without human inspection
• Better sensitivity than LC-MS for trace impurities
• Complete replacement of dissolution testing

Correct Answer: High throughput screening with minimal equipment and fast turnaround

Q25. Solvent saturation of a TLC development chamber is important because:

• It increases the boiling point of the mobile phase
• It creates a reproducible vapor atmosphere and reduces tailing
• It permanently modifies the stationary phase
• It eliminates the need to dry the plate

Correct Answer: It creates a reproducible vapor atmosphere and reduces tailing

Q26. Which TLC technique can help quantify drugs in complex matrices like plasma?

• Normal visualization only with iodine
• Coupling TLC with densitometry or TLC-MS after extraction and cleanup
• Running plates without sample preparation
• Using only water as mobile phase

Correct Answer: Coupling TLC with densitometry or TLC-MS after extraction and cleanup

Q27. Which plate handling practice reduces cross-contamination between samples?

• Spotting very close to each other
• Allowing spots to dry between applications and using separate micropipette tips
• Touching the plate surface with bare hands
• Using excessively concentrated samples only

Correct Answer: Allowing spots to dry between applications and using separate micropipette tips

Q28. Which solvent system would you try first for separating moderately polar drugs on silica TLC?

• Hexane only
• Chloroform:methanol in varying ratios
• Pure water
• Liquid nitrogen

Correct Answer: Chloroform:methanol in varying ratios

Q29. What is a common use of TLC in formulation development?

• Measuring tablet hardness directly
• Monitoring reaction progress, compatibility studies, and excipient interaction screening
• Measuring viscosity of creams
• Determining dissolution profile solely

Correct Answer: Monitoring reaction progress, compatibility studies, and excipient interaction screening

Q30. Which validation characteristic is essential for a quantitative TLC method used in pharmaceutical assay?

• Only visual distinctness of spots
• Linearity, accuracy, precision, specificity, and limit of detection/quantitation
• Use of radioactive tracers
• Elimination of mobile phase control

Correct Answer: Linearity, accuracy, precision, specificity, and limit of detection/quantitation

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com