Detection of heavy metals, pesticide residues and phytotoxins in herbs MCQs With Answer

Introduction

This quiz set focuses on detection of heavy metals, pesticide residues and phytotoxins in herbs — a critical area in Advanced Pharmacognosy-II for M.Pharm students. It covers analytical techniques, sample preparation, regulatory limits, matrix effects and interpretation of results. Questions emphasize practical laboratory approaches such as digestion methods, instrumental choices (AAS, ICP-MS, GC-MS, LC-MS/MS), modern extraction/cleanup strategies (QuEChERS, SPE), and challenges like speciation, interference and method validation (LOD/LOQ, recovery, CRMs). The objective is to strengthen conceptual understanding and analytical decision-making for ensuring herbal safety and compliance with quality standards in pharmaceutical practice.

Q1. Which instrumental technique is most suitable for multi-element trace quantification in herbal samples with the lowest detection limits?

• Flame atomic absorption spectrometry (FAAS)
• Graphite furnace atomic absorption (GFAAS)
• Inductively coupled plasma optical emission spectrometry (ICP-OES)
• Inductively coupled plasma mass spectrometry (ICP-MS)

Correct Answer: Inductively coupled plasma mass spectrometry (ICP-MS)

Q2. Which sample preparation method is commonly used for complete digestion of plant material before heavy metal analysis?

• Cold maceration with water
• Microwave-assisted acid digestion
• Soxhlet extraction with hexane
• Ultrasonic extraction with methanol

Correct Answer: Microwave-assisted acid digestion

Q3. For detecting organophosphate pesticide residues in herbs at ng/g levels, which analytical technique is preferred?

• High-performance liquid chromatography with UV detection (HPLC-UV)
• Gas chromatography with electron capture detector (GC-ECD)
• Gas chromatography–mass spectrometry (GC-MS) or GC-MS/MS
• Thin-layer chromatography (TLC)

Correct Answer: Gas chromatography–mass spectrometry (GC-MS) or GC-MS/MS

Q4. The QuEChERS method in pesticide analysis primarily refers to which combination of steps?

• Quick, Easy, Cheap, Effective, Rugged, and Safe extraction and cleanup
• Quantitative, Enzymatic, Chemical, Extraction, Standardization
• Quality, Equilibrium, Chromatography, Extraction, Solvent-free
• Quenching, Electrophoresis, Cleaning, Hydrolysis, Sample pooling

Correct Answer: Quick, Easy, Cheap, Effective, Rugged, and Safe extraction and cleanup

Q5. Which cleanup sorbent is commonly used in dispersive SPE (d-SPE) after QuEChERS to remove fatty interferences from herbal extracts?

• PSA (primary secondary amine)
• Celite
• Silica gel
• Activated carbon

Correct Answer: PSA (primary secondary amine)

Q6. When determining lead (Pb) at trace levels in herbs, which AAS mode increases sensitivity by reducing background and increasing atom residence time?

• Flame AAS
• Hydride generation AAS
• Graphite furnace AAS (GFAAS)
• Cold-vapor AAS

Correct Answer: Graphite furnace AAS (GFAAS)

Q7. Which phenomenon in ICP-MS causes false signals due to ions of different composition having the same mass-to-charge ratio and must be controlled?

• Ionization suppression
• Isobaric spectral interference
• Matrix precipitation
• Nonlinear calibration

Correct Answer: Isobaric spectral interference

Q8. For speciation analysis to distinguish inorganic arsenite (As III) from arsenate (As V) in herb extracts, which technique is most appropriate?

• Direct ICP-MS without separation
• Ion chromatography coupled to ICP-MS
• Flame photometry
• UV-Vis spectrophotometry after total digestion

Correct Answer: Ion chromatography coupled to ICP-MS

Q9. Which extraction technique is most appropriate for volatile pesticide residues and requires derivatization only rarely?

• Soxhlet extraction with dichloromethane
• Solid-phase microextraction (SPME) coupled to GC-MS
• Liquid-liquid extraction with methanol
• Pressurized hot water extraction

Correct Answer: Solid-phase microextraction (SPME) coupled to GC-MS

Q10. In method validation for residue analysis, what does LOD (limit of detection) represent?

• The lowest concentration that can be quantified with acceptable precision and accuracy
• The concentration above regulatory maximum residue limit (MRL)
• The lowest concentration that produces a measurable signal distinguishable from background noise
• The internal standard concentration used for calibration

Correct Answer: The lowest concentration that produces a measurable signal distinguishable from background noise

Q11. Pyrrolizidine alkaloids (PAs) in herbs are best screened and quantified using which technique?

• GC-MS without derivatization
• HPLC-UV at 254 nm
• LC-MS/MS with electrospray ionization (ESI)
• Colorimetric assay with ninhydrin

Correct Answer: LC-MS/MS with electrospray ionization (ESI)

Q12. Which regulatory document commonly provides maximum limits for heavy metals in herbal materials used in pharmaceuticals?

• ICH Q2(R1)
• WHO Guidelines on Good Agricultural and Collection Practices (GACP)
• USP and European Pharmacopoeia monographs
• ISO 9001

Correct Answer: USP and European Pharmacopoeia monographs

Q13. Matrix effects in LC-MS analysis of pesticide residues are typically addressed by which approach?

• Using external calibration with solvent standards only
• Ignoring matrix effects because they are negligible
• Using matrix-matched calibration or stable isotope-labeled internal standards
• Reducing injection volume to zero

Correct Answer: Using matrix-matched calibration or stable isotope-labeled internal standards

Q14. Which cleanup step is most effective for removing large molecular weight pigments from herb extracts prior to chromatographic analysis?

• Dilution with water
• Gel permeation chromatography (GPC)
• Adding sodium chloride
• Evaporation under vacuum

Correct Answer: Gel permeation chromatography (GPC)

Q15. Cyanogenic glycosides in certain herbs are typically detected by which analytical approach?

• Determination of released hydrogen cyanide by spectrophotometry or GC after hydrolysis
• Direct atomic absorption spectrometry
• ELISA for proteins
• ICP-OES for nitrogen content

Correct Answer: Determination of released hydrogen cyanide by spectrophotometry or GC after hydrolysis

Q16. Which of the following is an advantage of QuEChERS over traditional Soxhlet extraction for pesticide residues in herbs?

• Requires larger solvent volumes and longer time
• Provides cleaner extracts without any cleanup
• Faster, uses less solvent, and is adaptable to multi-residue analysis
• Only suitable for nonpolar pesticides

Correct Answer: Faster, uses less solvent, and is adaptable to multi-residue analysis

Q17. In heavy metal analysis, the standard addition method is particularly useful for which problem?

• Improving chromatographic resolution
• Correcting for matrix-induced signal suppression or enhancement
• Reducing the need for certified reference materials
• Increasing sample throughput

Correct Answer: Correcting for matrix-induced signal suppression or enhancement

Q18. Which phytotoxin is a glycoalkaloid commonly found in Solanaceae plants and may contaminate herbal materials?

• Atropine
• Solanine
• Cicutoxin
• Pyrrolizidine alkaloid

Correct Answer: Solanine

Q19. For routine monitoring of multiple pesticides in herbs, which detection mode in mass spectrometry provides the best combination of selectivity and quantitation accuracy?

• Single quadrupole full-scan MS
• Tandem mass spectrometry in multiple reaction monitoring (MRM) mode
• Time-of-flight MS with no fragmentation
• UV diode-array detection

Correct Answer: Tandem mass spectrometry in multiple reaction monitoring (MRM) mode

Q20. What is the purpose of using certified reference materials (CRMs) in trace contaminant analysis of herbs?

• To act as a sample preservative during storage
• To provide a matrix-free calibration standard
• To verify method accuracy, trueness and maintain traceability of results
• To replace the need for instrument calibration

Correct Answer: To verify method accuracy, trueness and maintain traceability of results

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