Instrumentation of flame emission spectroscopy MCQs With Answer

Instrumentation of flame emission spectroscopy MCQs With Answer

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Instrumentation of Flame Emission Spectroscopy MCQs With Answer

Flame emission spectroscopy (FES) remains a cornerstone technique for rapid, cost-effective quantification of alkali and alkaline earth metals in pharmaceutical analysis. For M. Pharm students, mastering its instrumentation is vital to understand sensitivity, selectivity, and precision in real-world assays. This quiz focuses on the core hardware and operational parameters: nebulizers, spray chambers, burner heads, fuel–oxidant systems, optical wavelength selectors, detectors, and safety controls. You will also test your understanding of flame stoichiometry, droplet dynamics, spectral bandwidth, viewing geometry, and strategies to mitigate ionization and spectral interferences. Each question emphasizes how specific components and settings affect signal quality and method robustness, helping you connect design principles to analytical performance.

Q1. In a flame emission spectrometer, the primary function of the nebulizer is to:

  • Heat the sample to excite atoms directly
  • Convert the liquid sample into a fine aerosol with a narrow droplet size distribution
  • Filter out interfering spectral lines
  • Amplify the emitted light signal

Correct Answer: Convert the liquid sample into a fine aerosol with a narrow droplet size distribution

Q2. The spray chamber placed after the nebulizer is mainly used to:

  • Increase flame temperature for better excitation
  • Remove large droplets and damp aspiration pulsations for a stable aerosol
  • Split the beam for dual-wavelength detection
  • Convert ions back to neutral atoms

Correct Answer: Remove large droplets and damp aspiration pulsations for a stable aerosol

Q3. Which burner type is most commonly used in flame emission spectroscopy for improved sensitivity and reproducibility?

  • Total consumption (concentric) burner
  • Premix long-slot burner
  • Bunsen-type open flame
  • Meker burner

Correct Answer: Premix long-slot burner

Q4. For measuring refractory or hard-to-excite elements, which fuel–oxidant pair provides the highest flame temperature among routine choices?

  • Air–acetylene
  • Nitrous oxide–acetylene (N₂O–C₂H₂)
  • Air–propane
  • Hydrogen–air

Correct Answer: Nitrous oxide–acetylene (N₂O–C₂H₂)

Q5. A long-slot premix burner is preferred in FES chiefly because it:

  • Increases optical path length and provides a stable, uniform flame for viewing
  • Allows direct introduction of solids without nebulization
  • Eliminates the need for wavelength selection
  • Reduces the requirement for flame safety interlocks

Correct Answer: Increases optical path length and provides a stable, uniform flame for viewing

Q6. In the wavelength selection system of FES, which optical element is primarily responsible for dispersion of emitted radiation?

  • Beam splitter
  • Diffraction grating
  • Neutral density filter
  • Achromatic lens

Correct Answer: Diffraction grating

Q7. The detector most commonly used in flame emission spectrometers due to its high gain and low noise is the:

  • Thermocouple
  • Photodiode array
  • Photomultiplier tube (PMT)
  • Bolometer

Correct Answer: Photomultiplier tube (PMT)

Q8. Decreasing the monochromator slit width in FES will generally:

  • Increase resolution but reduce signal intensity
  • Decrease both resolution and signal intensity
  • Increase both resolution and signal intensity
  • Have no effect on spectral interferences

Correct Answer: Increase resolution but reduce signal intensity

Q9. Emitted radiation from the flame is typically observed at 90 degrees to the flame axis because this geometry:

  • Maximizes the Doppler broadening
  • Minimizes direct flame background and stray light to the detector
  • Increases the aspiration rate of the nebulizer
  • Allows simultaneous multi-element detection without dispersion

Correct Answer: Minimizes direct flame background and stray light to the detector

Q10. An ionization buffer (e.g., excess K or Cs salt) is added in FES to:

  • Enhance nebulization efficiency of viscous samples
  • Suppress analyte ionization by providing electrons and stabilizing the plasma electron density
  • Increase the flame’s oxidizing power
  • Shift the analyte emission line to a longer wavelength

Correct Answer: Suppress analyte ionization by providing electrons and stabilizing the plasma electron density

Q11. For alkali metals like Na and K, which flame condition often minimizes ionization and improves emission intensity?

  • Strongly oxidizing air–acetylene flame
  • Fuel-rich (slightly reducing) air–acetylene flame
  • Nitrous oxide–acetylene flame under oxidizing conditions
  • Hydrogen–oxygen flame at maximum temperature

Correct Answer: Fuel-rich (slightly reducing) air–acetylene flame

Q12. The impact bead (or baffle) inside many spray chambers primarily serves to:

  • Increase droplet size for better drainage
  • Coalesce and remove larger droplets, narrowing the aerosol size distribution
  • Ionize the aerosol before entry into the flame
  • Reduce the solvent vapor pressure by cooling

Correct Answer: Coalesce and remove larger droplets, narrowing the aerosol size distribution

Q13. Clinical or dedicated Na/K flame photometers often use interference filters instead of full monochromators because filters:

  • Provide higher spectral resolution than gratings
  • Are simpler, have high throughput, and are adequate for isolated strong lines
  • Eliminate the need for detectors
  • Allow multi-element detection without moving parts

Correct Answer: Are simpler, have high throughput, and are adequate for isolated strong lines

Q14. If the sample uptake rate is increased well beyond the optimal range in FES, the most likely outcome is:

  • Lower noise due to improved droplet filtering
  • Increased background correction accuracy
  • Signal instability due to excess large droplets and poorer desolvation
  • No change in sensitivity but improved linearity

Correct Answer: Signal instability due to excess large droplets and poorer desolvation

Q15. A common background correction strategy in FES uses:

  • Deuterium lamp continuum subtraction
  • Zeeman modulation of the emission line
  • Off-peak measurement near the analytical line with electronic subtraction
  • Graphite furnace temperature programming

Correct Answer: Off-peak measurement near the analytical line with electronic subtraction

Q16. For effective spectral isolation, the selected spectral bandwidth in FES should be:

  • Wider than the separation between adjacent lines
  • Comparable to the flame’s continuum background width
  • Narrow enough to exclude nearby lines yet wide enough to pass the analyte line without excessive loss
  • Fixed at 2.0 nm for all elements

Correct Answer: Narrow enough to exclude nearby lines yet wide enough to pass the analyte line without excessive loss

Q17. Flame safety interlocks in FES instrumentation primarily:

  • Compensate for matrix effects by adjusting slit width
  • Shut off fuel/oxidant flows if flame-out or low gas pressure is detected
  • Correct spectral overlaps by switching filters
  • Increase flame temperature automatically for refractory analytes

Correct Answer: Shut off fuel/oxidant flows if flame-out or low gas pressure is detected

Q18. Compared with a premix slot burner, a total consumption burner generally offers:

  • Higher precision and lower noise
  • Better tolerance to high dissolved solids but poorer precision
  • Superior spectral resolution
  • Lower susceptibility to chemical interferences

Correct Answer: Better tolerance to high dissolved solids but poorer precision

Q19. In FES, using an internal standard (element not present in the sample) helps primarily to:

  • Increase the flame temperature
  • Correct for variations in aspiration rate, aerosol transport, and short-term flame fluctuations
  • Shift the analyte emission line to a non-interfering region
  • Eliminate the need for external calibration

Correct Answer: Correct for variations in aspiration rate, aerosol transport, and short-term flame fluctuations

Q20. With a premix air–acetylene burner, the emission is usually observed from the interconal region because this zone:

  • Has the highest concentration of molecular emitters
  • Contains the maximum population of free neutral atoms suitable for emission measurement
  • Is the coldest region, minimizing vaporization
  • Eliminates the need for wavelength selection

Correct Answer: Contains the maximum population of free neutral atoms suitable for emission measurement

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