Detection of heavy metals in herbal formulations MCQs With Answer

Introduction:

Detection of heavy metals in herbal formulations is a critical component of quality assurance in M.Pharm practice. This blog provides focused multiple-choice questions designed to reinforce theoretical knowledge and practical aspects of heavy metal analysis—covering sample preparation, instrumental methods (AAS, ICP-OES, ICP-MS, XRF), special techniques (cold vapor, hydride generation, graphite furnace), interferences, limits of detection/quantitation, and regulatory controls. Questions emphasize method selection, validation steps (matrix spikes, CRMs, internal standards), and on-site screening approaches. These MCQs are tailored for M.Pharm students preparing for exams in Herbal and Cosmetic Analysis (MPA 204T) and aim to deepen understanding of analytical strategies used to ensure safety of herbal products.

Q1. Which analytical technique provides the highest sensitivity and lowest detection limits for multielement trace analysis in herbal formulations?

• Flame Atomic Absorption Spectrometry (FAAS)
• Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)
• Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
• Energy Dispersive X-Ray Fluorescence (EDXRF)

Correct Answer: Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

Q2. Which sample preparation technique best minimizes the loss of volatile elements such as mercury during digestion of herbal samples?

• Open hot-plate wet digestion
• Dry ashing at high temperature
• Microwave-assisted closed-vessel acid digestion
• Fusion with sodium carbonate

Correct Answer: Microwave-assisted closed-vessel acid digestion

Q3. Which reagent is classically used to form a colored complex with nickel for selective colorimetric tests?

• Dithizone (diphenylthiocarbazone)
• Dimethylglyoxime (DMG)
• 8-Hydroxyquinoline
• Sodium rhodizonate

Correct Answer: Dimethylglyoxime (DMG)

Q4. Which analytical method is specifically adapted for sensitive determination of mercury via conversion to elemental vapor?

• Flame Atomic Absorption Spectrometry (FAAS)
• Cold Vapor Atomic Absorption Spectrometry (CV-AAS)
• ICP-OES
• Portable XRF

Correct Answer: Cold Vapor Atomic Absorption Spectrometry (CV-AAS)

Q5. Hydride generation is a specialized sample introduction technique commonly used for which group of elements?

• Lead and Cadmium
• Arsenic and Selenium
• Mercury and Chromium
• Copper and Zinc

Correct Answer: Arsenic and Selenium

Q6. The standard addition method is primarily applied in heavy metal analysis to correct for which analytical problem?

• Instrumental drift over time
• Matrix-induced signal suppression or enhancement
• Calibration curve non-linearity
• Low sample throughput

Correct Answer: Matrix-induced signal suppression or enhancement

Q7. Which expression correctly defines the limit of detection (LOD) used in quantitative trace metal analysis?

• LOD = average blank signal
• LOD = 3 × standard deviation of the blank divided by the calibration slope
• LOD = 10 × standard deviation of the blank divided by the calibration slope
• LOD = highest concentration of calibration standard

Correct Answer: LOD = 3 × standard deviation of the blank divided by the calibration slope

Q8. What is the commonly accepted operational definition of the limit of quantitation (LOQ)?

• LOQ = 2 × LOD
• LOQ = 5 × standard deviation of the blank divided by the slope
• LOQ = 10 × standard deviation of the blank divided by the calibration slope
• LOQ = concentration of the lowest calibration standard

Correct Answer: LOQ = 10 × standard deviation of the blank divided by the calibration slope

Q9. Which acid reagent combination is most commonly used in closed-vessel microwave digestion for organic herbal matrices prior to heavy metal analysis?

• Nitric acid (HNO3) alone
• Hydrochloric acid (HCl) alone
• Nitric acid (HNO3) with hydrogen peroxide (H2O2)
• Hydrofluoric acid (HF) with perchloric acid (HClO4)

Correct Answer: Nitric acid (HNO3) with hydrogen peroxide (H2O2)

Q10. To ensure analytical accuracy when quantifying heavy metals in complex herbal matrices, which material is recommended for method verification?

• An internal calibration standard only
• A certified reference material (CRM) with similar matrix
• A reagent blank
• A synthetic standard solution in pure water

Correct Answer: A certified reference material (CRM) with similar matrix

Q11. In ICP-MS arsenic at m/z 75 is prone to interference from which polyatomic ion commonly formed in plasma containing chloride?

• ArN+
• ArCl+
• Cl2+
• ArO+

Correct Answer: ArCl+

Q12. Which analytical technique allows rapid, non-destructive screening of elemental composition in solid herbal samples at the point of collection?

• ICP-MS
• Flame AAS
• Portable X-ray fluorescence (pXRF)
• Wet acid digestion followed by ICP-OES

Correct Answer: Portable X-ray fluorescence (pXRF)

Q13. Which instrument measures light emitted by excited atoms and ions and is often used for multi-element analysis of digested herbal samples?

• Graphite Furnace Atomic Absorption (GFAAS)
• Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)
• Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
• Cold Vapor AAS

Correct Answer: Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

Q14. Which chelating reagent is commonly used for selective extraction or colorimetric detection of lead in qualitative assays?

• Dimethylglyoxime (DMG)
• Dithizone (diphenylthiocarbazone)
• 2,2′-Bipyridyl
• EDTA

Correct Answer: Dithizone (diphenylthiocarbazone)

Q15. Regulatory heavy metal testing of herbal formulations typically requires specification of which set of elements as primary contaminants of concern?

• Lead, Cadmium, Chromium, Nickel
• Arsenic, Selenium, Zinc, Copper
• Lead, Cadmium, Mercury, Arsenic
• Mercury, Iron, Calcium, Magnesium

Correct Answer: Lead, Cadmium, Mercury, Arsenic

Q16. What is the principal purpose of adding an internal standard in ICP-MS measurements of herbal digests?

• To increase signal intensity of analytes
• To correct for instrumental sensitivity drift and some matrix effects
• To serve as the calibration standard for all elements
• To remove polyatomic interferences

Correct Answer: To correct for instrumental sensitivity drift and some matrix effects

Q17. Which statistical parameter is most commonly used to express the precision of replicate heavy metal determinations?

• Percent recovery
• Relative standard deviation (RSD)
• Bias
• Correlation coefficient (R)

Correct Answer: Relative standard deviation (RSD)

Q18. Matrix spike recovery experiments are performed primarily to evaluate which aspect of a heavy metal analytical method?

• Instrument detection limit
• Method accuracy in the presence of the sample matrix
• Repeatability of the instrument
• Volumetric calibration accuracy

Correct Answer: Method accuracy in the presence of the sample matrix

Q19. Which field-deployable technique is most suitable for rapid on-site screening of soil or plant material for heavy metal contamination before laboratory confirmation?

• Laboratory ICP-MS
• Portable X-ray fluorescence (pXRF)
• Graphite furnace AAS in the field
• Wet chemistry colorimetric assays for all metals

Correct Answer: Portable X-ray fluorescence (pXRF)

Q20. Compared to flame atomic absorption spectrometry (FAAS), graphite furnace AAS (GFAAS) typically offers which analytical advantage for trace metal determination in herbal extracts?

• Wider linear dynamic range but higher sample consumption
• Lower limits of detection and smaller sample volume required
• Multi-element simultaneous measurement capability
• Non-destructive analysis of solid samples

Correct Answer: Lower limits of detection and smaller sample volume required

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