Detection of pesticide residues in herbal formulations MCQs With Answer

Detection of pesticide residues in herbal formulations MCQs With Answer

Introduction: This quiz set focuses on analytical strategies for detecting pesticide residues in herbal formulations—an essential topic for M.Pharm students specializing in Herbal and Cosmetic Analysis. Questions cover sampling, extraction (including QuEChERS and SPE), chromatographic separation (GC, LC), detectors (ECD, NPD, MS/MS), matrix effects, derivatization, method validation (LOD, LOQ, recovery, precision), and regulatory considerations such as Codex and MRL concepts. The items are designed to deepen understanding of practical laboratory choices, cleanup techniques for complex herbal matrices, and interpretation of analytical data for reliable residue quantification and risk assessment.

Q1. Which extraction technique is most commonly recommended as a fast and versatile first-step for multiclass pesticide residue analysis in herbal matrices?

• Liquid-liquid extraction with hexane only
• QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe)
• Soxhlet extraction with dichloromethane for 24 hours
• Supercritical CO2 extraction without modifiers

Correct Answer: QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe)

Q2. In the QuEChERS workflow for herbal samples, which combination is typically used to induce phase separation after acetonitrile extraction?

• NaCl and MgSO4
• NaHCO3 and KCl
• Ammonium acetate and ethanol
• Citric acid and isopropanol

Correct Answer: NaCl and MgSO4

Q3. Which dispersive SPE sorbent is commonly added during QuEChERS cleanup to remove sugars and organic acids from plant-derived herbal matrices?

• Graphitized carbon black (GCB)
• Primary secondary amine (PSA)
• Florisil
• Strong cation exchange (SCX)

Correct Answer: Primary secondary amine (PSA)

Q4. For the analysis of thermally stable volatile pesticides in herbal formulations, which chromatographic method and detector combination is most appropriate?

• LC-MS/MS with electrospray ionization (ESI)
• GC coupled with Electron Capture Detector (ECD)
• HPTLC with UV detection
• Ion chromatography with conductivity detector

Correct Answer: GC coupled with Electron Capture Detector (ECD)

Q5. Which MS/MS acquisition mode is preferred for highly selective and sensitive quantitation of multiple pesticide residues in complex herbal matrices?

• Full-scan MS
• Selected Ion Monitoring (SIM)
• Multiple Reaction Monitoring (MRM)
• Time-of-flight (TOF) full spectrum

Correct Answer: Multiple Reaction Monitoring (MRM)

Q6. Which cleanup strategy is specifically helpful to remove high molecular weight lipids and pigments from herbal extracts prior to LC-MS/MS analysis?

• Gel Permeation Chromatography (GPC)
• Direct injection without cleanup
• Salting out with sodium chloride only
• Ultrafiltration through 0.45 µm PTFE

Correct Answer: Gel Permeation Chromatography (GPC)

Q7. When analyzing organophosphorus pesticides by GC-MS, which derivatization reagent is commonly used to improve volatility and stability of polar metabolites?

• N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)
• 2,4-dinitrophenylhydrazine (DNPH)
• Phenyl isothiocyanate (PITC)
• Diazomethane

Correct Answer: N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)

Q8. Which performance parameter defines the lowest concentration of a pesticide that can be measured with acceptable precision and accuracy in a validated method?

• Limit of Detection (LOD)
• Limit of Quantification (LOQ)
• Signal-to-noise ratio (S/N)
• Retention time reproducibility

Correct Answer: Limit of Quantification (LOQ)

Q9. What is the typical signal-to-noise ratio used to estimate the Limit of Detection (LOD) in chromatographic pesticide analysis?

• S/N ≈ 1:1
• S/N ≈ 3:1
• S/N ≈ 10:1
• S/N ≈ 20:1

Correct Answer: S/N ≈ 3:1

Q10. Which detector is particularly sensitive for halogenated pesticide residues and often used with GC for organochlorine pesticides?

• Electron Capture Detector (ECD)
• Nitrogen-Phosphorus Detector (NPD)
• Flame Ionization Detector (FID)
• UV-Vis Detector

Correct Answer: Electron Capture Detector (ECD)

Q11. In LC-MS/MS pesticide analysis of herbal extracts, which matrix-related problem causes suppression or enhancement of ion signals and must be evaluated?

• Detector drift
• Matrix effect
• Column bleed
• Retention time shift

Correct Answer: Matrix effect

Q12. Which sorbent is effective at removing chlorophyll and planar pigments from herbal extracts during cleanup but can also adsorb some analytes and must be used carefully?

• C18 silica
• Primary secondary amine (PSA)
• Graphitized carbon black (GCB)
• Strong anion exchange (SAX)

Correct Answer: Graphitized carbon black (GCB)

Q13. According to typical validation guidelines for pesticide residue methods, acceptable recovery for spiked herbal samples is commonly within which range?

• 20–40%
• 50–60%
• 70–120%
• 150–200%

Correct Answer: 70–120%

Q14. For confirmation of an individual pesticide identity using GC-MS in regulated residue analysis, which criterion is crucial besides retention time match?

• Matching of at least two characteristic ions and relative ion ratios
• Matching of UV spectrum
• Only mass accuracy within 1000 ppm
• Peak area greater than an internal standard

Correct Answer: Matching of at least two characteristic ions and relative ion ratios

Q15. Which reference provides internationally recognized maximum residue limits (MRLs) for pesticides that analytical labs often consult for herbal product safety?

• Pharmacopoeia of India only
• Codex Alimentarius
• ISO Guide 34
• ICH Q2(R1)

Correct Answer: Codex Alimentarius

Q16. Which internal standard strategy improves quantitation accuracy in LC-MS/MS pesticide analysis of complex herbal matrices?

• Using a single unlabeled surrogate for all pesticides
• Using stable isotope-labeled internal standards for each target analyte
• No internal standard and relying on external calibration only
• Using an unrelated compound that elutes at the void volume

Correct Answer: Using stable isotope-labeled internal standards for each target analyte

Q17. Which preservation measure should be applied to herbal samples intended for pesticide residue analysis to minimize degradation before testing?

• Store at room temperature exposed to light
• Freeze at −20 °C and protect from light
• Dry at 60 °C for 48 hours and store in open containers
• Soak in ethanol to preserve pesticides

Correct Answer: Freeze at −20 °C and protect from light

Q18. When using GC-MS in Selected Ion Monitoring (SIM) mode for screening pesticides in herbal extracts, what is a main trade-off compared to full-scan MS?

• SIM provides worse sensitivity but better mass accuracy
• SIM increases sensitivity for selected ions but reduces full-scan identification capability
• SIM eliminates the need for chromatographic separation
• SIM allows simultaneous quantitation and structural elucidation for unknowns

Correct Answer: SIM increases sensitivity for selected ions but reduces full-scan identification capability

Q19. For multiclass pesticide analysis by LC-MS/MS, which mobile phase additive often improves chromatographic peak shape and ionization for basic and neutral pesticides?

• 0.1% Formic acid in water and 0.1% formic acid in methanol/acetonitrile
• 10% Sodium chloride aqueous solution
• 1% Triethylamine only in water
• Pure water and pure methanol without modifiers

Correct Answer: 0.1% Formic acid in water and 0.1% formic acid in methanol/acetonitrile

Q20. Which of the following is a key reason to perform recovery experiments at multiple concentration levels during method validation for pesticide residues in herbal formulations?

• To determine the instrument’s maximum pressure tolerance
• To assess method accuracy and precision across the relevant analytical range
• To identify which pesticides are volatile
• To ensure the column lifetime is adequate

Correct Answer: To assess method accuracy and precision across the relevant analytical range

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