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</p> Signup and view all the answers

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

    <p>APPI</p> Signup and view all the answers

    Which mass spectrometry technique separates ions by flight time?

    <p>TOF</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</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</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</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</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</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</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</p> Signup and view all the answers

    In electrospray ionization, which type of molecules ionize best?

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

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

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

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

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

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

    <p>ESI</p> Signup and view all the answers

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

    <p>APPI</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</p> Signup and view all the answers

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

    <p>MALDI</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</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</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</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</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</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</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</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</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</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</p> Signup and view all the answers

    In UVPD, how does the fragmentation compare to CID?

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

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

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

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

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

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

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

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

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

    Which ionization technique is best suited for analyzing large biomolecules?

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

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

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

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

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

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

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

    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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    Description

    Test your knowledge on the ionization and fragmentation processes that occur during Electron Ionization (EI) in mass spectrometry. Learn about the use of a 70eV electron beam to ionize samples and the extensive fragmentation it can cause.

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