DART-MS analysis MCQs With Answer

Introduction: DART-MS analysis MCQs With Answer is a focused question set designed for M.Pharm students enrolled in Advanced Instrumental Analysis (MPA 201T). This blog presents 20 targeted multiple-choice questions that probe both fundamental and advanced concepts of Direct Analysis in Real Time Mass Spectrometry (DART-MS). Questions cover ionization mechanisms, instrumental parameters, coupling with mass analyzers, advantages, limitations, and practical pharmaceutical and forensic applications. Each question is followed by four options and the correct answer to aid quick self-assessment. The material emphasizes practical control of variables—such as gas type, temperature, dopants, and orifice voltages—to prepare students for lab work, method development, and critical data interpretation.

Q1. What does DART stand for?

• Direct Analysis in Real Time
• Direct Atmospheric Reaction Transfer
• Desorption Atmospheric Release Technique
• Direct Aqueous Reaction Technology

Correct Answer: Direct Analysis in Real Time

Q2. Which primary ionization mechanism is responsible for initiating analyte ion formation in DART?

• Penning ionization by metastable gas atoms followed by proton-transfer reactions
• Electron impact ionization in the ion source
• Electrospray ionization from a charged spray
• Matrix-assisted laser desorption/ionization (MALDI)

Correct Answer: Penning ionization by metastable gas atoms followed by proton-transfer reactions

Q3. Which carrier or discharge gas is most commonly used in DART experiments for efficient metastable formation?

• Helium
• Nitrogen
• Argon
• Air

Correct Answer: Helium

Q4. In positive-ion DART spectra of small organic drugs, which ion type is most commonly observed?

• Molecular radical cation M•+
• Protonated molecule [M+H]+
• Deprotonated molecule [M–H]–
• Chloride adduct [M+Cl]–

Correct Answer: Protonated molecule [M+H]+

Q5. What is the typical method for introducing a sample to a DART source?

• Direct exposure of the solid/liquid sample surface to the heated DART gas stream
• Injection through a GC column into the DART source
• Infusion through a conventional electrospray emitter
• Embedding into a MALDI matrix and laser desorption

Correct Answer: Direct exposure of the solid/liquid sample surface to the heated DART gas stream

Q6. Which instrumental parameter primarily controls the thermal desorption of analytes in DART?

• Gas heater temperature (DART gas temperature)
• Capillary voltage of the mass spectrometer
• Laser power at the ionization region
• pH of the sample matrix

Correct Answer: Gas heater temperature (DART gas temperature)

Q7. Which of the following is a major practical advantage of DART-MS for pharmaceutical analysis?

• Rapid ambient analysis with minimal or no sample preparation
• Guaranteed high quantitative precision without standards
• Exclusive suitability for high molecular weight proteins
• Requirement for chromatographic separation before MS

Correct Answer: Rapid ambient analysis with minimal or no sample preparation

Q8. Which statement best describes a common limitation of DART-MS in quantitative pharmaceutical assays?

• Quantitative reproducibility can be poor due to matrix effects and variable sample positioning
• DART-MS always produces excessive fragmentation making identification impossible
• DART cannot ionize small organic molecules below 200 Da
• DART requires cryogenic cooling for routine use

Correct Answer: Quantitative reproducibility can be poor due to matrix effects and variable sample positioning

Q9. Which type of mass analyzer is most frequently coupled with DART sources for high-throughput identification?

• Time-of-flight (TOF) mass analyzer
• Fourier-transform infrared spectrometer
• Standalone gas chromatograph
• Gel permeation chromatograph

Correct Answer: Time-of-flight (TOF) mass analyzer

Q10. Which ionization polarities can be used with DART to extend the range of detectable analytes?

• Both positive and negative ion modes
• Only positive ion mode
• Only negative ion mode
• Neutral detection only (no ions formed)

Correct Answer: Both positive and negative ion modes

Q11. How is DART best classified among ionization techniques?

• An ambient, generally soft ionization technique
• A hard ionization technique analogous to electron ionization
• A chromatographic separation method
• A laser-based matrix-assisted technique

Correct Answer: An ambient, generally soft ionization technique

Q12. What strategy is commonly used to improve ionization of analytes with low proton affinity in DART-MS?

• Introduce a dopant vapor to generate more favorable reagent ions
• Decrease the DART gas temperature to condense analytes
• Mix sample with MALDI matrix powder
• Use direct infusion electrospray instead of DART

Correct Answer: Introduce a dopant vapor to generate more favorable reagent ions

Q13. What is the role of metastable atoms generated in the DART gas discharge?

• They transfer excitation energy that initiates ionization (e.g., Penning ionization) of molecules or intermediates
• They serve solely to heat the sample without any chemical interaction
• They capture electrons to produce negative molecular ions directly
• They polymerize on the sample surface to aid desorption

Correct Answer: They transfer excitation energy that initiates ionization (e.g., Penning ionization) of molecules or intermediates

Q14. Formation of ammonium adducts like [M+NH4]+ in DART spectra is most often caused by what?

• Presence of ammonium-containing dopants or sample impurities
• Use of helium gas at low temperature
• Exposure to ultraviolet light in the source
• High vacuum levels in the MS pump

Correct Answer: Presence of ammonium-containing dopants or sample impurities

Q15. Which factor most strongly influences the limits of detection (LOD) in DART-MS analyses?

• Ionization efficiency and matrix/background chemical noise
• The brand of the mass spectrometer independent of ionization
• The color of the sample surface
• The use of columns for chromatographic separation

Correct Answer: Ionization efficiency and matrix/background chemical noise

Q16. Which class of analytes is generally least suitable for DART-MS direct analysis?

• Intact high‑molecular‑weight proteins (>10 kDa)
• Small-molecule drugs and metabolites
• Pesticide residues on surfaces
• Coated tablet surfaces and excipients

Correct Answer: Intact high‑molecular‑weight proteins (>10 kDa)

Q17. Which forensic application is DART-MS particularly well suited for?

• Rapid screening and presumptive identification of illicit drugs on surfaces
• Species identification by DNA sequencing
• Long-term storage of evidence at cryogenic temperatures
• Bulk elemental analysis of metals by XRF

Correct Answer: Rapid screening and presumptive identification of illicit drugs on surfaces

Q18. How is in-source collision-induced dissociation (CID) typically induced in DART-MS to obtain structural information?

• By increasing orifice/skimmer voltages or accelerating potentials to promote fragmentation
• By lowering the DART gas temperature to freeze fragments
• By adding a fluorescent dye to the sample matrix
• By switching to a continuous-wave laser in the source

Correct Answer: By increasing orifice/skimmer voltages or accelerating potentials to promote fragmentation

Q19. Which instrumental factors critically affect the efficiency of transferring DART-generated ions into the mass spectrometer?

• Orifice/skimmer voltages and gas flow geometry between DART source and MS inlet
• Color of the sample holder and ambient light levels
• Choice of chromatographic column stationary phase
• Presence of a MALDI matrix on the sample

Correct Answer: Orifice/skimmer voltages and gas flow geometry between DART source and MS inlet

Q20. Which approach most effectively improves quantitative performance for DART-MS assays in pharmaceutical analysis?

• Use of an isotopically labeled internal standard plus strict control of sample positioning and ionization conditions
• Increasing the DART gas temperature indefinitely to maximize signal
• Relying solely on single-point external calibration without internal standards
• Switching to a different gas each run without standardization

Correct Answer: Use of an isotopically labeled internal standard plus strict control of sample positioning and ionization conditions

Download