Need for extraction of drugs from biological matrices MCQs With Answer

Introduction: Extraction of drugs from biological matrices is a fundamental step in bioanalytical workflows used in pharmacokinetics, toxicology, therapeutic drug monitoring and drug development. Biological samples such as plasma, serum, urine or tissues contain proteins, lipids, salts and endogenous metabolites that can interfere with analytical measurements, reduce sensitivity and cause matrix effects on instruments like LC‑MS/MS. Proper extraction improves selectivity, concentrates analytes, enhances recovery and stabilizes labile drugs. This quiz set focuses on the reasons for extraction, common strategies (protein precipitation, liquid–liquid extraction, solid‑phase extraction, microextraction), and practical considerations such as matrix effects, sample stability and validation parameters important for M.Pharm students.

Q1. Why is extraction of drugs from biological matrices typically necessary before instrumental analysis?

• To change the color of the sample
• To remove interfering matrix components and enrich the analyte for accurate detection
• To increase sample volume for analysis
• To sterilize the sample

Correct Answer: To remove interfering matrix components and enrich the analyte for accurate detection

Q2. Which of the following best describes a major cause of ion suppression in LC‑MS/MS analyses of biological samples?

• High analyte concentration
• Co‑eluting endogenous phospholipids or salts from the matrix
• Use of high organic mobile phase
• Overly dilute samples

Correct Answer: Co‑eluting endogenous phospholipids or salts from the matrix

Q3. Protein precipitation is often used as a sample preparation step because it primarily serves to:

• Completely purify analytes from all matrix components
• Remove proteins and reduce sample viscosity while being simple and high‑throughput
• Concentrate trace analytes by selective binding
• Derivatize analytes for better detection

Correct Answer: Remove proteins and reduce sample viscosity while being simple and high‑throughput

Q4. Compared to protein precipitation, solid‑phase extraction (SPE) is preferred when the aim is to:

• Quickly remove proteins with minimal equipment
• Achieve higher selectivity, cleaner extracts and analyte concentration
• Perform colorimetric assays directly on the sample
• Evaporate the sample to dryness rapidly

Correct Answer: Achieve higher selectivity, cleaner extracts and analyte concentration

Q5. Liquid–liquid extraction (LLE) effectiveness depends mainly on which factor?

• The color of the solvent
• The partition coefficient of the drug between aqueous and organic phases and pH of the aqueous phase
• The brand of glassware used
• The type of detector downstream

Correct Answer: The partition coefficient of the drug between aqueous and organic phases and pH of the aqueous phase

Q6. A major advantage of microextraction techniques (e.g., SPME, DLLME) over conventional LLE is:

• They always require larger sample volumes
• They are more solvent‑consuming
• They offer miniaturization, solvent reduction and often better enrichment factors
• They eliminate the need for instrument calibration

Correct Answer: They offer miniaturization, solvent reduction and often better enrichment factors

Q7. Which parameter during method validation quantifies the effect of matrix on ionization in LC‑MS/MS?

• Limit of detection (LOD)
• Matrix factor or percent matrix effect
• Retention time reproducibility
• pH stability

Correct Answer: Matrix factor or percent matrix effect

Q8. For highly protein‑bound drugs, which sample preparation consideration is most important to measure unbound concentrations?

• Using LLE to extract total drug only
• Applying ultrafiltration or equilibrium dialysis to separate free drug from protein‑bound fraction
• Using only SPE without considering binding
• Adding acid to denature the analyte

Correct Answer: Applying ultrafiltration or equilibrium dialysis to separate free drug from protein‑bound fraction

Q9. During extraction method development, why is pH adjustment of the biological sample commonly performed?

• To denature the analyte
• To change the analyte ionization state and improve partitioning into organic solvent or binding to sorbent
• To promote microbial growth
• To change color for visual inspection

Correct Answer: To change the analyte ionization state and improve partitioning into organic solvent or binding to sorbent

Q10. Which sorbent type would you select in SPE to retain basic drugs selectively?

• Nonpolar C18 without any ionic functionality
• Strong cation exchange (SCX) sorbent
• Strong anion exchange (SAX) sorbent
• Silica gel only

Correct Answer: Strong cation exchange (SCX) sorbent

Q11. In the context of bioanalytical extraction, the term “recovery” refers to:

• The percentage of sample lost during transport
• The percentage of analyte recovered from the matrix after the extraction process relative to the initial amount
• The time required to perform extraction
• The color change after extraction

Correct Answer: The percentage of analyte recovered from the matrix after the extraction process relative to the initial amount

Q12. Which preservation step is important when collecting blood samples for labile drug analysis?

• Leaving samples at room temperature for several hours
• Adding stabilizers or preservatives and immediate cold storage to prevent degradation
• Exposing samples to sunlight
• Adding proteases to speed up metabolism

Correct Answer: Adding stabilizers or preservatives and immediate cold storage to prevent degradation

Q13. QuEChERS is a sample preparation approach particularly noted for which advantages?

• Being very slow and reagent‑intensive
• Quick, easy, cheap, effective, rugged and safe extraction suitable for complex matrices like tissues or food
• Only used for protein quantification
• Only applicable to gaseous samples

Correct Answer: Quick, easy, cheap, effective, rugged and safe extraction suitable for complex matrices like tissues or food

Q14. Which extraction technique is most suitable when minimal solvent use and direct coupling to GC or LC are desired?

• Large‑scale liquid–liquid extraction with multiple washes
• Solid‑phase microextraction (SPME)
• Boiling the sample
• Adding excess salts only

Correct Answer: Solid‑phase microextraction (SPME)

Q15. When designing an extraction for LC‑MS/MS quantitation at very low concentrations, which strategy is most important?

• Maximize matrix complexity to increase signal
• Maximize analyte enrichment and reduce matrix background to improve signal‑to‑noise and LLOQ
• Avoid any cleanup steps
• Use only UV detection

Correct Answer: Maximize analyte enrichment and reduce matrix background to improve signal‑to‑noise and LLOQ

Q16. Which factor is least likely to be improved by a better extraction/cleanup procedure?

• Selectivity and reduction of interfering peaks
• Matrix‑induced ion suppression
• Intrinsic chemical instability of the analyte in the matrix if not stabilized
• Signal‑to‑noise ratio by removing background

Correct Answer: Intrinsic chemical instability of the analyte in the matrix if not stabilized

Q17. In bioanalytical assays, internal standards are used during extraction primarily to:

• Provide an external calibration only
• Correct for extraction variability, matrix effects and instrument variability
• Change the analyte retention time
• Act as a preservative

Correct Answer: Correct for extraction variability, matrix effects and instrument variability

Q18. Ultrafiltration as a sample preparation method is mainly used to:

• Extract analytes into organic solvent
• Separate low molecular weight free drug from high molecular weight components like proteins
• Derivatize analytes for GC analysis
• Concentrate samples by heating

Correct Answer: Separate low molecular weight free drug from high molecular weight components like proteins

Q19. Which solvent property is most critical when choosing an organic solvent for LLE of a neutral lipophilic drug?

• Boiling point only
• High miscibility with water
• Low dielectric constant and immiscibility with water to promote extraction into organic phase
• Color matching the analyte

Correct Answer: Low dielectric constant and immiscibility with water to promote extraction into organic phase

Q20. During method transfer of an extraction procedure between labs, which aspect is most critical to ensure comparable results?

• Exact replication of consumables, sample handling, pH, solvent grades and validated recovery/matrix factor data
• Only matching the instrument brand
• Changing sample volume arbitrarily
• Ignoring storage conditions

Correct Answer: Exact replication of consumables, sample handling, pH, solvent grades and validated recovery/matrix factor data

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