Sample interview questions: Explain your understanding of the principles behind various mass spectrometry techniques.
Sample answer:
1. Ionization Techniques:
– Electrospray Ionization (ESI): Gentle ionization technique that preserves non-covalent interactions, suitable for analyzing polar and labile compounds.
– Matrix-Assisted Laser Desorption/Ionization (MALDI): Soft ionization technique that allows analysis of large biomolecules, such as proteins and peptides.
– Atmospheric Pressure Chemical Ionization (APCI): Ionization method that generates ions in atmospheric pressure, suitable for analyzing small molecules and compounds with low volatility.
2. Mass Analyzers:
– Time-of-Flight (TOF): Measures the time it takes ions to travel a known distance, providing accurate mass measurement and high mass-to-charge ratio (m/z) range.
– Quadrupole Mass Analyzer: Utilizes four parallel rods to selectively allow ions of specific m/z ratios to pass through, enabling mass filtering and analysis.
– Ion Trap: Traps ions and manipulates them using radio frequency fields, allowing for selective ion storage, isolation, and fragmentation.
– Fourier Transform Ion Cyclotron Resonance (FT-ICR): Measures the frequency of ion cyclotron resonance, providing ultra-high mass accuracy and resolution, making it suitable for complex mixture analysis.
3. Tandem Mass Spectrometry (MS/MS):
– Collision-Induced Dissociation (CID): Fragments ions by high-energy collisions with neutral gas, generating product ions that provide structural information about the precursor ion.
– Electron Transfer Dissociation (ETD): Transfers electrons from a radical anion to the precursor ion, inducing fragmentation while preserving labile modifications.
– Higher-Energy Collisional Dissociation (HCD): Similar to CID but uses higher collision energies, resulting in more extensive fragmentation, often used for peptide sequencing.
– Infrared Multiphoton Dissociation (IRMPD): Utilizes infrared radiation to induce fragmentation, providing complementary fragmentation patterns to CID and ETD, useful for structural characterization.
4. Data Interpretation and Analysis:
– Qualitative Analysis: Identifies the compounds present in… Read full answer
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