Solid phase extraction (SPE) MCQs With Answer

Introduction: Solid phase extraction (SPE) MCQs With Answer

SPE (Solid Phase Extraction) is a cornerstone sample-preparation technique widely used in bioanalytical laboratories to isolate, concentrate, and clean analytes from complex biological matrices. For M.Pharm students, mastering SPE involves understanding sorbent chemistries (reversed-phase, normal-phase, ion-exchange, mixed-mode), cartridge formats, and critical steps—conditioning, loading, washing, and elution. This quiz set focuses on practical and theoretical aspects relevant to LC-MS/MS bioanalysis, method development, troubleshooting, and validation. Emphasis is placed on parameters that affect recovery, selectivity, matrix effects, breakthrough volume, solvent strength, and automation strategies to prepare you for research and industry applications.

Q1. What is the primary purpose of the conditioning step in an SPE protocol?

• To remove analytes retained on the sorbent
• To equilibrate the sorbent with a solvent similar to the sample matrix
• To elute polar interferents prior to sample loading
• To dry the sorbent completely before sample application

Correct Answer: To equilibrate the sorbent with a solvent similar to the sample matrix

Q2. Which sorbent type is most suitable for extracting weak basic drugs from plasma when using pH adjustment to ensure reversible retention?

• Reversed-phase C18
• Strong cation-exchange (SCX)
• Strong anion-exchange (SAX)
• Normal-phase silica

Correct Answer: Strong cation-exchange (SCX)

Q3. Which statement best describes “breakthrough volume” in SPE?

• The volume of eluent required to completely desorb analytes from the sorbent
• The maximum sample volume that can pass through the sorbent without loss of the analyte
• The solvent volume needed to rinse salts and polar impurities
• The volume of sorbent packed into a cartridge

Correct Answer: The maximum sample volume that can pass through the sorbent without loss of the analyte

Q4. Which sorbent property most directly influences retention when using reversed-phase SPE for neutral analytes?

• Surface acidity
• Hydrophobicity (carbon load)
• Ion-exchange capacity
• Particle porosity only

Correct Answer: Hydrophobicity (carbon load)

Q5. Which elution strategy would you choose to release strongly retained basic analytes from a C18 sorbent?

• Use a weak aqueous buffer at neutral pH
• Use a strong organic solvent containing a small amount of base
• Elute with pure water
• Increase flow rate without changing solvent composition

Correct Answer: Use a strong organic solvent containing a small amount of base

Q6. What advantage do polymeric SPE sorbents (e.g., Oasis HLB) offer over silica-based C18 sorbents?

• Lower chemical stability in organic solvents
• Better pH stability and broader polarity range
• Exclusive selectivity for highly polar analytes only
• Higher ionic exchange capacity by default

Correct Answer: Better pH stability and broader polarity range

Q7. In SPE method development, which parameter is most critical to reduce matrix effects for LC-MS analysis?

• Selecting a larger cartridge housing
• Optimizing wash solvent composition to remove matrix interferences
• Using the strongest possible elution solvent
• Eliminating the conditioning step

Correct Answer: Optimizing wash solvent composition to remove matrix interferences

Q8. For an acidic analyte (pKa ~4.5), which sample pH will generally increase retention on a reversed-phase sorbent?

• pH 2.0
• pH 4.5
• pH 7.5
• pH 10.0

Correct Answer: pH 2.0

Q9. Which SPE format is most suitable for high-throughput bioanalysis with automated liquid handling?

• Glass column cartridges
• Syringe-based manual cartridges
• 96-well SPE plates
• Single large-bed disk filters

Correct Answer: 96-well SPE plates

Q10. What is the primary mechanism of retention for mixed-mode SPE sorbents?

• Hydrophobic interactions only
• Electrostatic interactions only
• Combination of hydrophobic and ion-exchange interactions
• Size-exclusion based on particle diameter

Correct Answer: Combination of hydrophobic and ion-exchange interactions

Q11. During SPE, a strong washing step removes matrix components but also decreases analyte recovery. Which adjustment is most appropriate?

• Increase loading flow rate
• Reduce wash solvent strength or volume
• Skip conditioning step
• Use a larger bed mass without changing wash

Correct Answer: Reduce wash solvent strength or volume

Q12. Which factor most affects the capacity of an SPE cartridge for a given analyte?

• Particle color
• Sorbent bed mass and surface area
• Cartridge outer diameter
• Length of the elution tube only

Correct Answer: Sorbent bed mass and surface area

Q13. For an ion-exchange SPE, how is the analyte typically eluted after retention?

• By increasing ionic strength or changing pH to neutralize charge
• By decreasing solvent polarity only
• By cooling the cartridge to precipitate matrix
• By sonicating the cartridge in buffer

Correct Answer: By increasing ionic strength or changing pH to neutralize charge

Q14. What is the main disadvantage of using excessively large SPE bed masses for trace-level analytes?

• Lower overall analyte capacity
• Increased solvent consumption and potential dilution during elution
• Complete elimination of matrix effects
• Faster processing times

Correct Answer: Increased solvent consumption and potential dilution during elution

Q15. Which monitoring parameter is essential during SPE method validation specific to recovery assessment?

• Column oven temperature
• Absolute and relative recovery across concentration range
• Color of the eluate only
• Manufacturer lot number of SPE cartridge only

Correct Answer: Absolute and relative recovery across concentration range

Q16. When coupling on-line SPE to LC-MS, what is the critical consideration for choosing SPE elution solvent?

• Elution solvent must be immiscible with LC mobile phase
• Elution solvent must be compatible with the LC mobile phase and MS source
• Elution solvent must be strongly basic only
• Elution solvent should have the highest possible UV absorbance

Correct Answer: Elution solvent must be compatible with the LC mobile phase and MS source

Q17. Which of these practices helps minimize carryover between successive SPE samples?

• Using the same cartridge for different sample types without washing
• Performing thorough wash steps and using blank runs between samples
• Increasing sample loading volume dramatically
• Eluting with water only

Correct Answer: Performing thorough wash steps and using blank runs between samples

Q18. Which characteristic of analytes makes disk SPE preferable to cartridge SPE?

• Extremely low molecular weight below 50 Da only
• Requirement for processing large sample volumes rapidly
• Need for very high backpressure tolerance
• When analytes are volatile gases

Correct Answer: Requirement for processing large sample volumes rapidly

Q19. In SPE, which analytical complication is most likely if the sample solvent is much stronger (more organic) than the conditioning/wash solvent?

• Enhanced sorbent activation
• Reduced retention and possible analyte loss during loading
• Improved matrix removal automatically
• Increased cartridge shelf life

Correct Answer: Reduced retention and possible analyte loss during loading

Q20. Which parameter best describes selectivity improvement when switching from C18 to mixed-mode SPE for polar basic compounds?

• Only increased hydrophobic retention
• Combination of hydrophobic and ionic interactions enhances retention and selectivity
• Elimination of all matrix interferences regardless of wash
• Exclusive retention by size exclusion

Correct Answer: Combination of hydrophobic and ionic interactions enhances retention and selectivity

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