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
