Electron Ionization (EI) Ionization and Fragmentation Processes Quiz

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Questions and Answers

Which ionization technique uses electron bombardment, causing fragmentation?

  • MALDI
  • EI (correct)
  • ESI
  • APPI

What is the best ionization technique for large biomolecules?

  • APPI
  • ESI
  • MALDI (correct)
  • EI

Which ionization technique involves proton/electron transfer from a solid mixed with matrix?

  • ESI
  • MALDI (correct)
  • APPI
  • EI

Which mass spectrometry technique has the highest resolution up to 10 million?

<p>FT-ICR (B)</p> Signup and view all the answers

Which ionization technique uses photoionization of reagent gas to induce analyte ionization?

<p>APPI (B)</p> Signup and view all the answers

Which mass spectrometry technique separates ions by flight time?

<p>TOF (A)</p> Signup and view all the answers

What type of analytes are best suited for analysis by APPI compared to electrospray ionization?

<p>Non-polar compounds (D)</p> Signup and view all the answers

How does APPI ionize analyte molecules that have ionization energies higher than the lamp output?

<p>By using a reagent gas to transfer energy and produce ions (D)</p> Signup and view all the answers

What is the role of reagent gas in APPI?

<p>To produce ions from the analyte molecules through reactions (C)</p> Signup and view all the answers

How does ESI produce multiple charged ions from analyte molecules?

<p>By forming highly charged droplets that undergo fission (D)</p> Signup and view all the answers

Why is multiple charging significant in mass spectrometry?

<p>It helps in detecting high mass analytes outside the detection range (A)</p> Signup and view all the answers

What happens as highly charged droplets shrink in size during ESI?

<p>The charge becomes concentrated on the analyte molecules (D)</p> Signup and view all the answers

What is the main purpose of the third quadrupole in mass spectrometry?

<p>To provide a sensitive and selective detection mode for targeted analytes (C)</p> Signup and view all the answers

In electrospray ionization, which type of molecules ionize best?

<p>Polar, charged molecules (D)</p> Signup and view all the answers

What is one key advantage of matrix-assisted laser desorption ionization (MALDI) compared to other techniques?

<p>Simple spectra (A)</p> Signup and view all the answers

What factor plays a significant role in influencing the resolution of a mass spectrometer?

<p>Ion kinetic energy spread (A)</p> Signup and view all the answers

How does Fourier transform ion cyclotron resonance (FT-ICR) achieve high resolution in mass spectrometry?

<p>By trapping ions in a magnetic field and exciting their cyclotron motion (D)</p> Signup and view all the answers

What principle does ion mobility spectrometry rely on to separate ions?

<p>Drift time in buffer gas (B)</p> Signup and view all the answers

What is the main function of a time-of-flight (TOF) mass analyzer?

<p>Separating ions based on their m/z ratios (D)</p> Signup and view all the answers

How does an orbitrap mass analyzer achieve high mass resolution?

<p>By trapping ions between an inner spindle and outer barrel electrostatically (B)</p> Signup and view all the answers

"Which of the following factors does NOT influence the ionization efficiency of an analyte in electrospray ionization?"

<p>Analyte volatility (B)</p> Signup and view all the answers

What is the main limitation of matrix-assisted laser desorption ionization (MALDI)?

<p>Limited mass accuracy (B)</p> Signup and view all the answers

How does a quadrupole mass analyzer selectively transmit ions based on their m/z?

<p>By applying both RF and DC voltages to four parallel rods and scanning RF/DC voltages to allow ions with specific m/z to traverse based on stable trajectory (D)</p> Signup and view all the answers

What is a key advantage of ion trap mass analyzers over quadrupole mass analyzers?

<p>Higher trapping efficiencies and multi-stage MS/MS capabilities (D)</p> Signup and view all the answers

How does time-of-flight mass spectrometry achieve high resolving power and mass accuracy?

<p>By separating ions based on their time-of-flight down a field-free drift tube (D)</p> Signup and view all the answers

What structural information does ion mobility spectrometry (IMS) provide compared to conventional mass spectrometry?

<p>Charge and rotationally averaged collision cross section information (B)</p> Signup and view all the answers

What does infrared multiphoton dissociation (IRMPD) induce in ions?

<p>Energy deposition through absorption of IR photons for peptide backbone cleavages (A)</p> Signup and view all the answers

How does Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) detect ions?

<p>By trapping ions in a magnetic field and exciting their cyclotron motion with an electric field (C)</p> Signup and view all the answers

What does ultraviolet photodissociation (UVPD) induce in ions compared to CID?

<p>More amide backbone cleavages through absorption of multiple UV photons (A)</p> Signup and view all the answers

What role does multiple reaction monitoring (MRM) mode play in triple quadrupole mass spectrometers?

<p>Isolating precursor ions in the first quadrupole and fragmenting them in the second quadrupole via CID (C)</p> Signup and view all the answers

How is mass defect used to determine molecular formulas from high-resolution mass spectra?

<p>By using isotopic patterns and mass defects to calculate possible molecular formulas within a certain error threshold (D)</p> Signup and view all the answers

Which mass spectrometry technique offers high resolution and accuracy at a lower cost than FT-ICR?

<p>EI (B)</p> Signup and view all the answers

Which ionization method is best suited for analyzing volatile thermally-stable compounds?

<p>ESI (D)</p> Signup and view all the answers

Which mass spectrometry technique forms charged droplets that undergo coulombic fission?

<p>APPI (D)</p> Signup and view all the answers

Which mass spectrometry technique is known for having the highest resolution up to 10 million?

<p>FT-ICR (D)</p> Signup and view all the answers

Which ionization technique involves proton/electron transfer from a solid mixed with matrix?

<p>MALDI (C)</p> Signup and view all the answers

Which mass spectrometry technique separates ions by flight time and provides very high resolution up to 100,000?

<p>TOF (B)</p> Signup and view all the answers

What is the role of the reagent gas in atmospheric pressure photoionization (APPI)?

<p>Transferring energy to ionize the analytes (D)</p> Signup and view all the answers

Why does electrospray ionization (ESI) work better than APPI for polar compounds?

<p>The charge becomes concentrated on the analyte molecules in ESI (B)</p> Signup and view all the answers

How does APPI ionize molecules with ionization energies higher than the lamp output?

<p>By transferring energy to the analyte molecules through reactions (A)</p> Signup and view all the answers

In electrospray ionization (ESI), why are highly charged ions more readily dissociated during tandem MS experiments?

<p>Highly charged ions have stronger coulombic interactions (D)</p> Signup and view all the answers

What is a key difference between atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) in terms of ionizing analytes?

<p>APPI forms singly charged ions, while ESI forms multiple charged ions (C)</p> Signup and view all the answers

What makes multiple charging significant in mass spectrometry when analyzing high mass analytes?

<p>**Highly charged ions are more readily dissociated during tandem MS experiments (C)</p> Signup and view all the answers

What advantage do ion trap mass analyzers offer over quadrupole mass analyzers?

<p>Multi-stage MS/MS capabilities (B)</p> Signup and view all the answers

How do ions get separated in ion mobility spectrometry (IMS)?

<p>By their drift times in an electric field (D)</p> Signup and view all the answers

What is the main limitation of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)?

<p>Limited mass range (A)</p> Signup and view all the answers

In UVPD, how does the fragmentation compare to CID?

<p>More amide backbone cleavages (B)</p> Signup and view all the answers

What does Reflectron TOF use to improve resolution in time-of-flight mass spectrometry?

<p>Ion mirror (C)</p> Signup and view all the answers

How is mass defect utilized in determining molecular formulas from high-resolution mass spectra?

<p>It reflects isotopic patterns (A)</p> Signup and view all the answers

What type of dissociation occurs in infrared multiphoton dissociation (IRMPD) compared to CID?

<p>Cleavages along peptide backbone (B)</p> Signup and view all the answers

What does a quadrupole mass analyzer offer over an ion trap analyzer?

<p>Wider mass range (C)</p> Signup and view all the answers

What principle does time-of-flight mass spectrometry rely on for ion separation?

<p>Drift times in an electric field (A)</p> Signup and view all the answers

How does multiple reaction monitoring (MRM) mode differ from standard analysis in triple quadrupole mass spectrometers?

<p>Precursor ion isolation only (B)</p> Signup and view all the answers

What is the primary function of the third quadrupole in mass spectrometry?

<p>Transmit only one fragment ion to the detector (D)</p> Signup and view all the answers

In electrospray ionization, which type of analyte molecules ionize the best?

<p>Polar, charged molecules (B)</p> Signup and view all the answers

How does matrix-assisted laser desorption ionization (MALDI) produce gas phase ions from solid samples?

<p>Laser ablation of solid sample mixed with matrix (A)</p> Signup and view all the answers

What is the key principle in ion separation in a quadrupole mass filter?

<p>RF and AC voltages (D)</p> Signup and view all the answers

Why is time-of-flight (TOF) mass analyzer known for its high resolution capabilities?

<p>Pulsed ion injection for m/z dependent flight times (B)</p> Signup and view all the answers

What does Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry trap ions in?

<p>A magnetic field (A)</p> Signup and view all the answers

What role does ion mobility spectrometry play when coupled with mass spectrometry?

<p>Providing structural information based on drift time in buffer gas (A)</p> Signup and view all the answers

How do orbitrap mass analyzers achieve high mass resolution?

<p>By trapping ions electrostatically and inducing radial oscillations (D)</p> Signup and view all the answers

What additional information does ion mobility spectrometry provide when coupled with mass spectrometry?

<p>Structural details based on drift time in buffer gas (C)</p> Signup and view all the answers

What does MALDI primarily use to ablate solid samples mixed with UV-absorbing matrix?

<p>Laser energy (D)</p> Signup and view all the answers

What role does the reagent gas play in atmospheric pressure photoionization (APPI)?

<p>It helps in transferring energy to produce ions from analyte molecules (A)</p> Signup and view all the answers

Why does electrospray ionization (ESI) work better than APPI for polar compounds?

<p>Polar compounds are less likely to form multiple charged ions in ESI (A)</p> Signup and view all the answers

What is the primary reason that highly charged ions are more readily dissociated during tandem MS experiments?

<p>Highly charged ions have concentrated charge on analyte molecules (D)</p> Signup and view all the answers

In electrospray ionization (ESI), what happens as highly charged droplets shrink in size?

<p>The charge becomes concentrated on the analyte molecules (C)</p> Signup and view all the answers

What is the significance of multiple charging in mass spectrometry when analyzing high mass analytes?

<p>It allows detection of high mass analytes within the instrument's detection range (D)</p> Signup and view all the answers

What type of compounds are best suited for analysis by atmospheric pressure photoionization (APPI) compared to electrospray ionization?

<p>Non-polar compounds difficult to ionize by ESI (A)</p> Signup and view all the answers

Which mass spectrometry technique offers the highest resolution up to 10 million?

<p>Fourier Transform Ion Cyclotron Resonance (FT-ICR) (C)</p> Signup and view all the answers

What is the main function of a quadrupole mass analyzer?

<p>Selective ion transmission based on m/z (B)</p> Signup and view all the answers

Which ionization technique is best suited for analyzing large biomolecules?

<p>Matrix-Assisted Laser Desorption Ionization (MALDI) (B)</p> Signup and view all the answers

In mass spectrometry, which technique forms charged droplets that undergo coulombic fission?

<p>Electrospray Ionization (ESI) (B)</p> Signup and view all the answers

What is a key advantage of Time-of-Flight (TOF) mass spectrometry compared to Quadrupole mass analyzers?

<p>Separates ions by flight time (D)</p> Signup and view all the answers

Which ionization technique uses photoionization of reagent gas to induce analyte ionization?

<p>Atmospheric Pressure Photoionization (APPI) (B)</p> Signup and view all the answers

How does a quadrupole mass analyzer selectively transmit ions based on their m/z?

<p>By scanning RF/DC voltages and amplitudes (B)</p> Signup and view all the answers

What is the main advantage of ion trap mass analyzers over quadrupole mass analyzers?

<p>High trapping efficiencies (D)</p> Signup and view all the answers

How does time-of-flight mass spectrometry achieve high resolving power and mass accuracy?

<p>By separating ions based on their flight time down a drift tube (B)</p> Signup and view all the answers

What additional information does ion mobility spectrometry provide compared to conventional mass spectrometry?

<p>Collision cross section of ions (A)</p> Signup and view all the answers

How does infrared multiphoton dissociation (IRMPD) differ from collision-induced dissociation (CID) in terms of fragmentation?

<p>IRMPD causes extensive cleavages along the peptide backbone (D)</p> Signup and view all the answers

How is mass defect utilized in determining molecular formulas from high-resolution mass spectra?

<p>It calculates possible molecular formulas based on isotopic patterns (C)</p> Signup and view all the answers

What is one key strength of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)?

<p>Extremely high resolution and accurate mass measurements (C)</p> Signup and view all the answers

What does ultraviolet photodissociation (UVPD) primarily induce in ions compared to CID?

<p>More amide backbone cleavages (C)</p> Signup and view all the answers

What is the principle of operation for ion mobility spectrometry (IMS)?

<p>Separates ions based on drift times in an electric field (C)</p> Signup and view all the answers

How does infrared multiphoton dissociation (IRMPD) differ from collision-induced dissociation (CID) in terms of fragmentation?

<p>IRMPD induces cleavages along the weakest bonds (D)</p> Signup and view all the answers

What is the main advantage of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers over other types?

<p>High resolution and accurate mass measurement (C)</p> Signup and view all the answers

In ion mobility spectrometry (IMS), what property of ions determines their drift time in the buffer gas?

<p>Collision cross section (C)</p> Signup and view all the answers

What is a key limitation of time-of-flight (TOF) mass analyzers compared to other mass analyzer types?

<p>Limited mass range (A)</p> Signup and view all the answers

Which factor plays a crucial role in achieving high resolution in a mass spectrometer using orbitrap technology?

<p>Flight path length (C)</p> Signup and view all the answers

What is a characteristic feature of matrix-assisted laser desorption ionization (MALDI) spectra?

<p>Simple spectra with high reproducibility (D)</p> Signup and view all the answers

How does a quadrupole mass filter function as a mass analyzer?

<p>By selectively transmitting ions based on stable trajectory (D)</p> Signup and view all the answers

One of the key advantages of ion mobility spectrometry (IMS) coupled with mass spectrometry (MS) is its ability to:

<p>Provide additional structural information (A)</p> Signup and view all the answers

Which factor does NOT significantly influence the resolution of a mass spectrometer?

<p>$pK_a$ values of analytes (A)</p> Signup and view all the answers

'High resolution, accuracy, and duty cycle' are the key strengths of which type of mass analyzer?

<p>Time-of-flight mass analyzer (D)</p> Signup and view all the answers

What is the primary function of the third quadrupole in a mass spectrometer?

<p>Transmission of fragment ions to the detector (A)</p> Signup and view all the answers

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Study Notes

Quadrupole Mass Analyzer

  • Consists of four parallel rods with RF and DC voltages applied
  • Ions with specific m/z traverse the quadrupole based on their stable trajectory, filtering out others
  • Scanned voltages build up a mass spectrum one m/z at a time

Ion Trap Mass Analyzer

  • Offers high trapping efficiencies, multi-stage MS/MS capabilities, and ion storage/accumulation
  • Limited mass range and susceptible to space charge effects
  • Contrasted with quadrupole analyzers: wider mass range, faster scan speeds, and less susceptible to space charge

Time-of-Flight Mass Spectrometry (TOF-MS)

  • Separates ions based on time-of-flight down a field-free drift tube
  • Ions of the same m/z reach the detector at the same time, regardless of kinetic energy
  • Long flight path improves separation; Reflectron TOF increases effective flight path length

Ultraviolet Photodissociation (UVPD)

  • Deposits energy into ions through absorption of multiple UV photons
  • Induces dissociation through direct bond cleavages, resulting in more amide backbone cleavages compared to CID

Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS)

  • Traps ions in a magnetic field, exciting their cyclotron motion with an electric field
  • Induces a detectable image current, yielding extremely high resolution mass spectra
  • Offers the highest resolution and most accurate mass measurements

Ion Mobility Spectrometry (IMS)

  • Separates ions in a buffer gas based on drift times, depending on charge and rotationally averaged collision cross section
  • Provides additional structural information to mass alone
  • IMS-MS aids compound identification for applications like proteomics and metabolomics

Infrared Multiphoton Dissociation (IRMPD)

  • Deposits energy into ions through absorption of multiple IR photons, inducing cleavages along the weakest bonds
  • Results in more extensive fragmentation than low-energy CID, often cleaving along the peptide backbone

Mass Defect

  • Difference between the exact mass of an atom or molecule and its whole mass unit assignment
  • Used to calculate possible molecular formulas from ultrahigh resolution spectra within a certain error threshold

Multiple Reaction Monitoring (MRM)

  • Isolates precursor ions in the first quadrupole, fragments them via CID in the second quadrupole
  • Transmits only one fragment ion to the detector in the third quadrupole
  • Provides a sensitive, selective detection mode for targeted analytes and metabolites in complex samples for quantitative purposes

Electron Ionization (EI)

  • Uses a 70eV electron beam to ionize samples, causing extensive fragmentation
  • Incident electrons eject outer shell electrons, leaving the sample with a net positive charge
  • Excited species undergo unimolecular decomposition, ejecting molecular fragments

Electrospray Ionization (ESI)

  • Produces multiple charged ions from analyte molecules in solution
  • Multiple charging occurs due to concentration of charge on analyte molecules during solvent evaporation and coulombic fission
  • Allows detection of high mass analytes with m/z values outside the instrument's detection range

Atmospheric Pressure Photoionization (APPI)

  • Uses a krypton or xenon discharge lamp to ionize a reagent gas, transferring energy to produce ions from the analyte molecules
  • Suited for non-polar compounds that are difficult to ionize by ESI

Matrix-Assisted Laser Desorption Ionization (MALDI)

  • Uses a laser to ablate a solid sample mixed with a UV-absorbing matrix

  • Matrix absorbs laser energy and transfers protons to analyte molecules, forming mainly [M+H]+ ions

  • Key advantages: ability to analyze non-volatile biomolecules and simple spectra; limitations: limited mass accuracy and reproducibility between shots### Ionization Techniques

  • EI (Electron Ionization) uses a 70eV electron beam to ionize samples, causing extensive fragmentation and producing characteristic fragmentation patterns.

  • EI is best for volatile thermally-stable compounds.

  • MALDI (Matrix-Assisted Laser Desorption Ionization) uses a laser to ablate a solid sample mixed with an UV-absorbing matrix, producing mainly [M+H]+ ions.

  • MALDI is suited for large biomolecules.

  • ESI (Electrospray Ionization) forms charged droplets that undergo coulombic fission, producing multiple charged ions.

  • ESI is suited for polar compounds in liquid samples.

  • APPI (Atmospheric Pressure Photoionization) uses photoionization of reagent gas to induce analyte ionization.

  • APPI is suited for non-polar compounds that are difficult to ionize by ESI.

Mass Analyzers

  • TOF (Time-of-Flight) separates ions by their time of flight down a field-free drift tube, offering high resolution up to 100,000, fast analysis, and a wide m/z range.
  • Quadrupole separates ions by selectively transmitting ions of a given m/z using RF and DC voltages, offering a simple design, robustness, and high sensitivity and speed for scanning.
  • FT-ICR (Fourier Transform Ion Cyclotron Resonance) detects image current from ion cyclotron resonance, offering the highest resolution up to 10 million and excellent mass accuracy.

Mass Spectrometry Techniques

  • IRMPD (Infrared Multiphoton Dissociation) deposits energy into ions through absorption of multiple photons, inducing cleavages along the weakest bonds.
  • UVPD (Ultraviolet Photodissociation) deposits energy into ions through absorption of multiple UV photons, inducing dissociation through direct bond cleavages.
  • CID (Collision-Induced Dissociation) involves vibrational activation and lower energy cleavages, often retaining side chains.
  • MRM (Multiple Reaction Monitoring) mode is used in triple quadrupole mass spectrometers for targeted, quantitative analysis.

Ion Mobility Spectrometry

  • IMS separates ions by drift time in a buffer gas, which depends on rotationally averaged collision cross section.
  • IMS provides additional structural information to mass spectrometry, aiding compound identification in applications like proteomics and metabolomics.

Mass Defect and Molecular Formulas

  • Mass defect is the difference between the exact mass of an atom or molecule and its whole mass unit assignment.
  • Isotopic patterns and mass defects can be used to calculate possible molecular formulas from ultrahigh resolution spectra within a certain error threshold.

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