Immobilized polysaccharide CSPs MCQs With Answer

Immobilized Polysaccharide CSPs MCQs With Answer

Introduction: This set of MCQs is designed for M.Pharm students studying Advanced Instrumental Analysis (MPA 201T) to deepen understanding of immobilized polysaccharide chiral stationary phases (CSPs). The questions cover chemistry of polysaccharide selectors (cellulose, amylose derivatives), immobilization chemistries, mechanisms of chiral recognition (H‑bonding, π–π, steric effects), solvent compatibility, column robustness, characterization methods and practical aspects for analytical and preparative separations. These items emphasize conceptual understanding and application, including column care, mobile phase selection, and interpretation of chromatographic parameters, preparing students for exam questions and real‑world method development using immobilized polysaccharide CSPs.

Q1. What is the principal practical advantage of an immobilized polysaccharide CSP compared with a traditionally coated polysaccharide CSP?

• Higher chiral selectivity for all analytes regardless of solvent
• Broader solvent compatibility allowing use of solvents like dichloromethane and chloroform
• Lower cost of manufacture due to simpler chemistry
• Ability to operate only in aqueous mobile phases

Correct Answer: Broader solvent compatibility allowing use of solvents like dichloromethane and chloroform

Q2. Which derivatized polysaccharide selector is commonly used in modern immobilized CSPs for reversed‑phase and normal‑phase separations?

• Polyvinyl alcohol
• Cellulose tris(3,5‑dimethylphenylcarbamate)
• Polyethylene glycol
• Silica bonded C18

Correct Answer: Cellulose tris(3,5‑dimethylphenylcarbamate)

Q3. What chemical strategy is most typically employed to immobilize a polysaccharide derivative onto silica?

• Physical adsorption by solvent casting and drying
• Covalent attachment to silica via a silane coupling agent and reactive linker chemistry
• Polymer entanglement with silica nanoparticles
• Electrostatic adsorption using charged surfactants

Correct Answer: Covalent attachment to silica via a silane coupling agent and reactive linker chemistry

Q4. How does immobilization generally affect the conformational mobility of polysaccharide selectors and its impact on chiral recognition?

• Immobilization increases flexibility and always improves enantioselectivity
• Immobilization decreases chain mobility, which can alter or sometimes reduce enantioselectivity depending on analyte
• Immobilization has no effect on selector conformation or selectivity
• Immobilization converts polysaccharide into a nonchiral material

Correct Answer: Immobilization decreases chain mobility, which can alter or sometimes reduce enantioselectivity depending on analyte

Q5. Which mobile phase solvent is typically NOT compatible with coated polysaccharide CSPs but is tolerated by many immobilized polysaccharide CSPs?

• n‑Hexane
• Isopropanol
• Dichloromethane
• Acetonitrile

Correct Answer: Dichloromethane

Q6. Why are immobilized polysaccharide CSPs often preferred for supercritical fluid chromatography (SFC)?

• They dissolve readily in supercritical CO2 providing a homogeneous stationary phase
• Their covalent attachment gives better stability toward high pressure CO2 and a wide range of organic modifiers
• They eliminate the need for organic modifiers in SFC
• They are only compatible with pure CO2 and no co‑solvents

Correct Answer: Their covalent attachment gives better stability toward high pressure CO2 and a wide range of organic modifiers

Q7. Which reactive linkage is commonly used in the chemical immobilization of phenylcarbamate‑derivatized polysaccharides onto aminated silica?

• Hydrophobic adsorption via alkyl chains
• Carbamate/urethane linkages formed by reaction of isocyanates with hydroxyl or amino groups
• Silanol exchange to form siloxane esters
• Simple ionic pairing between charged groups

Correct Answer: Carbamate/urethane linkages formed by reaction of isocyanates with hydroxyl or amino groups

Q8. Which chromatographic parameter is defined as the ratio of retention factors of two enantiomers (k2/k1) and is a measure of separation power?

• Resolution (Rs)
• Selectivity factor (α)
• Theoretical plates (N)
• Tailing factor (Tf)

Correct Answer: Selectivity factor (α)

Q9. Which combination of techniques is most appropriate to confirm successful immobilization of a polysaccharide selector on silica?

• UV‑Vis spectroscopy alone
• Elemental analysis, FTIR, solid‑state NMR and thermogravimetric analysis (TGA)
• Gas chromatography with flame ionization detection
• Conductivity and pH measurement of the packing suspension

Correct Answer: Elemental analysis, FTIR, solid‑state NMR and thermogravimetric analysis (TGA)

Q10. Which cleaning procedure is generally acceptable for immobilized CSPs but would damage coated CSPs?

• Washing with aqueous buffer at neutral pH
• Extended flushing with dichloromethane or chloroform
• Using only nonpolar hydrocarbon solvents like hexane
• Flushing with mild alcohols like methanol

Correct Answer: Extended flushing with dichloromethane or chloroform

Q11. Chiral recognition on polysaccharide CSPs arises from which set of interactions?

• Only steric hindrance effects
• Hydrogen bonding, π–π interactions, dipole interactions and steric complementarity
• Only ionic interactions
• Only hydrophobic van der Waals interactions

Correct Answer: Hydrogen bonding, π–π interactions, dipole interactions and steric complementarity

Q12. How does increasing column temperature typically affect enantioselectivity on polysaccharide CSPs?

• It generally increases enantioselectivity because chiral interactions strengthen with temperature
• It generally decreases enantioselectivity due to weakening of specific chiral interactions
• Temperature has no predictable effect on enantioselectivity
• It always converts enantiomers into diastereomers on the CSP

Correct Answer: It generally decreases enantioselectivity due to weakening of specific chiral interactions

Q13. Why are immobilized polysaccharide CSPs advantageous for preparative chiral separations?

• They are cheaper to pack at preparative scale than coated phases
• The immobilization permits use of a wider range of solvents and harsher cleaning, enabling robust scale‑up and solvent choice for solubility
• They provide infinite loading capacity without breakthrough
• They eliminate the need for downstream solvent removal

Correct Answer: The immobilization permits use of a wider range of solvents and harsher cleaning, enabling robust scale‑up and solvent choice for solubility

Q14. What is the typical support material used for immobilized polysaccharide CSPs in HPLC columns?

• Dense nonporous glass beads
• Porous silica particles with controlled pore size and high surface area
• Pure polymer beads with no silica
• Metallic fiber meshes

Correct Answer: Porous silica particles with controlled pore size and high surface area

Q15. In the context of immobilized CSPs, what does “immobilized” precisely refer to?

• Physically entrapped selector molecules in a polymer matrix without covalent bonds
• Covalent attachment of the derivatized polysaccharide selector to the chromatographic support
• Selector molecules freely dissolved in the mobile phase
• Selector present as a thin liquid film that can be washed away

Correct Answer: Covalent attachment of the derivatized polysaccharide selector to the chromatographic support

Q16. The term “bleed” in chiral CSPs refers to loss of selector from the column. Which statement is correct regarding bleed in immobilized versus coated polysaccharide CSPs?

• Immobilized CSPs typically show more bleed than coated phases
• Coated CSPs often show detectable selector bleed whereas immobilized CSPs minimize bleed under aggressive solvent conditions
• Neither coated nor immobilized CSPs ever exhibit bleed
• Bleed is only a problem in gas chromatography and not relevant to HPLC CSPs

Correct Answer: Coated CSPs often show detectable selector bleed whereas immobilized CSPs minimize bleed under aggressive solvent conditions

Q17. How do 3,5‑disubstituted phenylcarbamate groups on cellulose or amylose influence chiral recognition?

• They only reduce solubility and have no effect on chiral recognition
• They modulate steric and electronic environments, tuning π‑interactions and hydrogen bonding to enhance selectivity for many analytes
• They eliminate any possibility of hydrogen bonding interactions
• They convert the polysaccharide into a crystalline nonfunctional polymer

Correct Answer: They modulate steric and electronic environments, tuning π‑interactions and hydrogen bonding to enhance selectivity for many analytes

Q18. Which mobile phase additive is commonly used to reduce tailing of basic analytes on polysaccharide CSPs?

• Trifluoroacetic acid (TFA)
• Diethylamine (DEA) or other basic additives
• Potassium chloride
• EDTA

Correct Answer: Diethylamine (DEA) or other basic additives

Q19. Which of the following is NOT a typical advantage of immobilized polysaccharide CSPs?

• Increased tolerance to a wide variety of organic solvents
• Improved column robustness and easier cleaning with aggressive solvents
• Guaranteed improvement of enantioselectivity for every analyte compared with the coated analog
• Better compatibility with SFC and preparative separations due to solvent flexibility

Correct Answer: Guaranteed improvement of enantioselectivity for every analyte compared with the coated analog

Q20. What is the best practical approach to monitor the operational lifetime of an immobilized polysaccharide CSP in routine analytical use?

• Measure bed porosity once and assume constant performance
• Periodically inject a standard racemate and track retention times, selectivity (α) and resolution (Rs) after cleaning/regeneration cycles
• Only visually inspect the column slurry for discoloration
• Replace the column after a fixed number of injections without performance checks

Correct Answer: Periodically inject a standard racemate and track retention times, selectivity (α) and resolution (Rs) after cleaning/regeneration cycles

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