Principle and application of paper chromatography MCQs With Answer

Principle and application of paper chromatography MCQs With Answer offers M. Pharm students clear, exam-focused practice on one of the most versatile separation techniques in pharmaceutical analysis. Paper chromatography relies on partitioning of analytes between a water-rich stationary phase bound to cellulose and a mobile solvent, enabling separation of amino acids, sugars, alkaloids, and many drugs. This quiz emphasizes mechanism, method variables (paper grade, humidity, pH, solvent strength), development modes (ascending, descending, two-dimensional, reversed-phase), and detection strategies (ninhydrin, iodine, Dragendorff’s). Each MCQ is crafted to test conceptual understanding and practical decision-making, including troubleshooting spot shapes, improving resolution, quantitation by elution, and choosing solvent systems. Use these questions to reinforce fundamentals and sharpen analytical technique selection skills.

Q1. What is the fundamental principle governing separations in standard paper chromatography?

• Partition of solutes between a stationary aqueous phase on cellulose and a mobile solvent phase
• Adsorption of solutes onto silica gel sites
• Size exclusion based on molecular sieving through pores
• Affinity binding to immobilized ligands

Correct Answer: Partition of solutes between a stationary aqueous phase on cellulose and a mobile solvent phase

Q2. In paper chromatography, the stationary phase is best described as:

• Hydrophilic cellulose retaining a thin water layer via hydrogen bonding
• Free-flowing water reservoir at the bottom of the chamber
• Nonpolar paraffin-coated layer as default stationary phase
• Crosslinked polyacrylamide gel network

Correct Answer: Hydrophilic cellulose retaining a thin water layer via hydrogen bonding

Q3. The retention factor (Rf) in paper chromatography is defined as:

• Distance traveled by solute divided by distance traveled by solvent front
• Distance traveled by solvent front divided by origin-to-paper edge
• Distance from origin to solvent level at start
• Logarithm of partition coefficient

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

Q4. Why is chamber saturation important before development?

• Saturating the chamber with solvent vapor increases reproducibility and reduces solvent front curvature
• Keeping the chamber unsaturated improves resolution by sharpening fronts
• High humidity always increases Rf in normal-phase paper chromatography
• Chamber saturation is only required for descending development

Correct Answer: Saturating the chamber with solvent vapor increases reproducibility and reduces solvent front curvature

Q5. Which statement about ascending vs. descending paper chromatography is correct?

• Descending development uses gravity, allowing longer path lengths and higher resolution
• Ascending development generally runs faster and gives longer paths than descending
• Descending development requires solvent reservoir above the start line and is limited to short runs
• Ascending development eliminates capillary action

Correct Answer: Descending development uses gravity, allowing longer path lengths and higher resolution

Q6. Two-dimensional paper chromatography (2D-PC) is primarily used to:

• Develop in one solvent, dry, rotate 90°, develop in a second solvent to resolve co-migrating spots
• Use two solvents simultaneously from orthogonal edges
• Use thicker paper only
• Only applicable to inorganic ions

Correct Answer: Develop in one solvent, dry, rotate 90°, develop in a second solvent to resolve co-migrating spots

Q7. The RM value commonly used in paper chromatography is defined as:

• RM = log10[(1/Rf) − 1]
• RM = 1/Rf
• RM = −log10(Rf)
• RM = (distance to solvent front − distance to spot)/distance to solvent front

Correct Answer: RM = log10[(1/Rf) − 1]

Q8. Which visualization reagent is most appropriate for amino acids on paper chromatography?

• Ninhydrin gives purple to blue-violet coloration with most amino acids
• Iodine vapor gives permanent brown spots for amino acids
• Bromothymol blue sprays produce fluorescent spots for amino acids
• Dragendorff’s reagent is preferred for amino acids

Correct Answer: Ninhydrin gives purple to blue-violet coloration with most amino acids

Q9. A widely used solvent system for separating sugars by paper chromatography is:

• n-Butanol: acetic acid: water (4:1:5, upper phase)
• Hexane: ethyl acetate (1:1)
• Chloroform: methanol (99:1)
• Toluene: ammonia (9:1)

Correct Answer: n-Butanol: acetic acid: water (4:1:5, upper phase)

Q10. How does ambient humidity typically affect Rf values in normal-phase paper chromatography?

• Increasing ambient humidity increases water on paper and tends to decrease Rf in normal-phase systems
• Increasing humidity dries the paper and increases Rf
• Humidity has no effect on Rf
• Only affects detection, not migration

Correct Answer: Increasing ambient humidity increases water on paper and tends to decrease Rf in normal-phase systems

Q11. What is the expected effect of mobile phase pH on the migration of basic drugs in paper chromatography?

• Raising mobile phase pH tends to increase Rf of basic drugs by reducing ionization
• Raising pH decreases Rf of basic drugs due to increased positive charge
• Rf of bases is independent of pH
• pH only affects acids, not bases

Correct Answer: Raising mobile phase pH tends to increase Rf of basic drugs by reducing ionization

Q12. Which statement correctly describes reversed-phase paper chromatography?

• Paper impregnated with nonpolar material creates a nonpolar stationary phase and polar mobile phase
• Standard paper chromatography already operates in reversed-phase mode
• Reversed-phase PC uses silica gel plates
• Nonpolar impregnation reduces retention of nonpolar solutes in all cases

Correct Answer: Paper impregnated with nonpolar material creates a nonpolar stationary phase and polar mobile phase

Q13. Which is a best practice for sample application in paper chromatography?

• Apply small concentrated spots/bands with capillaries on a pencil-drawn baseline above solvent level
• Use ink to mark the start line for better visibility
• Immerse the origin below solvent level to ensure rapid wetting
• Apply large volumes to create wider spots for better detection

Correct Answer: Apply small concentrated spots/bands with capillaries on a pencil-drawn baseline above solvent level

Q14. An analyte migrates 6.0 cm from the origin, and the solvent front is at 9.5 cm. What is its Rf?

• 0.63
• 1.58
• 0.16
• 0.95

Correct Answer: 0.63

Q15. Why are chromatography chambers often lined with solvent-wetted filter paper during equilibration?

• To shorten equilibration time and provide reproducible solvent activity
• To prevent capillary action in paper
• To stabilize temperature by insulation only
• To reduce background fluorescence from paper

Correct Answer: To shorten equilibration time and provide reproducible solvent activity

Q16. Which reagent is most suitable for detecting alkaloids on paper chromatograms?

• Dragendorff’s reagent produces orange-brown complexes with many alkaloids
• Ninhydrin gives red-brown color with alkaloids
• Iodine vapor specifically stains alkaloids only
• Ferric chloride is the most selective for alkaloids

Correct Answer: Dragendorff’s reagent produces orange-brown complexes with many alkaloids

Q17. What is a key benefit of using an internal standard/marker in paper chromatography?

• Co-develop a marker with known Rf to correct for day-to-day variation and enable tentative identification
• Internal standards are avoided because they smear
• Use as diluent to reduce spot spreading but not for identification
• Required only when using descending technique

Correct Answer: Co-develop a marker with known Rf to correct for day-to-day variation and enable tentative identification

Q18. Which statement about paper grade selection is correct?

• Whatman No. 1 is the most commonly used qualitative chromatography paper for general separations
• Whatman 3MM is thin and low-capacity, used for micro PC only
• Whatman No. 1 has hydrophobic surface by default
• All paper grades give identical flow characteristics

Correct Answer: Whatman No. 1 is the most commonly used qualitative chromatography paper for general separations

Q19. How can ion-pairing agents modify migration of ionic drugs in paper chromatography?

• Adding a cationic ion-pair reagent to the mobile phase can increase Rf of anionic drugs by forming neutral ion-pairs
• Ion-pair reagents decrease migration of oppositely charged analytes by precipitation
• Ion-pairing only affects UV detection, not migration
• Ion-exchange cannot be achieved on paper

Correct Answer: Adding a cationic ion-pair reagent to the mobile phase can increase Rf of anionic drugs by forming neutral ion-pairs

Q20. Which is an appropriate application of paper chromatography in pharmaceutical analysis?

• Fingerprinting complex herbal extracts and assessing purity of drug substances
• Determining melting point of solids
• Measuring partition coefficient by shake-flask
• Sterility testing of injectables

Correct Answer: Fingerprinting complex herbal extracts and assessing purity of drug substances

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