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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5925_Библиотеки_им_академика_М_И_Перельмана.pdf
9.3 Instrumentation 391
• Compact design: Ion traps are smaller and more affordable than other mass
analyzers such as TOF or FT-ICR.
• MS/MS capability: Capable of performing tandem mass spectrometry (MS/MS),
allowing for fragm ent ion analysis and structural elucidation.
• Wide mass range: Can detect a broad range of ion masses, making it versatile for
various applications.
9.3.3.6.5 Limitations
• Lower mass resolution: Compared to analyzers such as TOF and FT-ICR, ion
traps have lower mass resolving power.
• Space charge effects: High ion populations in the trap can cause space charge
effects, distorting the mass spectrum.
• Limited mass accuracy: Compared to high-precision analyzers such as FT-ICR,
ion traps may offer lower mass accuracy.
9.3.3.6.6 Applications
• Proteomics and metabolomics: Used for peptide and protein analysis, as well as
metabolic profiling.
• Environmental analysis: Detects trace levels of contaminants and pollutants.
• Pharmaceutical research: Analyzes drug metabolites and helps in drug discovery
and development.
• Forensic science : Ideal
for detecting
and quantifying small molecules in forensic
samples, such as drugs and toxins.
9.3.3.7 Magnetic Sector Analyzer
The magnetic sector analyzer utilizes the principle of electromagnetic fields to
separate ions based on their m/z ratios. Ions are accelerated through an electric
field and then subjected to a magnetic field, which causes them to follow a curved
path. The radius of this curvature is dependent on the m/z ratio of the ions, allowing
for their separation and subsequent detection.
9.3.3.7.1 Components
1. Ion source: Generates ions that will be analyzed.
2. Accelerator: Applies a volt age to accelerate the ions
to a
specific kinetic energy.
3. Magnetic field: Created by a magnet, it deflects the accelerated ions along a
curved path.
4. Detector: Measures the arrival of ions and quantifies them based on their m/z
ratio.
9.3.3.7.2 How it Works
1. Ion generation: Ions
produced in the ion source, often using techniques such
are
as electron impact or chemical ionization.
2. Acceleration: The
ions are accelerated by an electric field, imparting them with
kinetic energy.
392 9 Comprehensive Insights into Mass Spectrometry
3. Deflection: As the accelerated ions enter the magnetic field, they are deflected
according to their mass-to-charge ratio. Lighter ions will curve more sharply than
heavier ions.
4. Detection: Ions strike the detector at different positions based on their m/z ratios.
The resulting data is used to create a mass spectrum.
9.3.3.7.3 Advantages
• High resolution: Magnetic
analyzers can achieve very high mass resolu-
sector
tion, allowing for the accurate distinction between ions with similar m/z ratios.
• High mass accuracy: They provide excellent mass accuracy due to their precise
measurement capabilities.
• Robustness: Magnetic sector instruments tend to be robust and stable, with lower
susceptibility to noise compared to some other mass analyzers.
9.3.3.7.4
Limitations
• Size and weight: These instruments can be large and heavy, making them less
portable than other types of mass spectrometers.
• Cost: Magnetic sector analyzers are often more expensive to purchase and
maintain compared to simpler mass spectrometry systems.
• Longer analysis time: The time required to analyze samples can be longer
compared to faster systems such as TOF analyzers.
9.3.3.7.5 Applications
• Isotope analysis: Used in geochemistry and environmental studies for isotopic
ratio analysis.
• Environmental monitoring: Effective for detecting and quantifying pollutants and
contaminants.
• Pharmaceutical development: Employed in drug development to
molecules
and metabolites with high precision.
analyze small
• Metallurgy and materials science: Utilized for the analysis of metals and alloys,
particularly in determining trace elemental compositions.
9.3.3.8 Orbitrap Analyzer
The Orbitrap analyzer utilizes a n electrostatic field to trap ions in an orbital motion
around a central spindle. Ions are introduced into the Orbitrap, where they are
trapped and oscillate at specific frequencies based on their mass-to-charge (m/z)
ratios. The frequencies of these oscillations are then measured to determine the mass
of the ions.
9.3.3.8.1 Components
• Ion source: Produces ions through
• Ion trap: A
spindle-shaped
techniques such
central electrode surrounded by a pair of outer
electrodes that creates an electric field to trap the ions.
• Detector: Measures the
oscillation frequencies of the trapped ions, providing data
for mass analysis.
as ESI or MALDI.
9.3 Instrumentation 393
• Vacuum system: Maintains a low-pressure environment to allow ions to travel
without colliding with gas molecules.
9.3.3.8.2 How it Works
• Ion generation: Ions are generated in the ion source and introduced into the
Orbitrap.
• Trapping: The ions are trapped within the electric field, where they begin to
oscillate in a specific manner.
• Frequency measurement: As the ions oscillate, they produce an
electric signa
l. The frequency of this signal is directly related to the m/z ratio
oscillating
of
the ions.
• Mass
spectrum generation: The detected frequencies are converted into a mass
spectrum, representing the different ions present in the sample.
9.3.3.8.3 Advantages
• High resolution: The Orbitrap can achieve very high mass resolution, allowing
for the accurate identification of ions with very similar m/z ratios.
• High mass accuracy: It provides excellent mass accuracy due to its precise
frequency measurements.
• Wide dynamic range: The Orbitrap can detect ions over a wide range of
concentrations, making it suitable for complex samples.
• Versatility: Can be coupled with various ionization techniques and is suitable for
both small molecules and
large biomolecules.
9.3.3.8.4
Limitations
• Cost: Orbitrap analyzers can be expensive to purchase and maintain compared to
other mass spectrometers.
• Complexity: The interpretation of data can be complex, requiring sophisticated
software and expertise.
• Analysis time: While generally faster than some other high-resoluti
may still require longer acquisition times than simpler systems.
it
on techniques,
9.3.3.8.5 Applications
• Proteomics: Widely used in proteomics for
protein
identification and quan ti fica-
tion due to its high resolution and mass accuracy.
• Metabolomics: Effective for analyzing met
abolites in
biological samples,
providing insights into metabolic pathways and disease mechanisms.
• Pharmaceutical analysis: Use d in drug development to study drug metabolism
and pharmacokinetics.
• Environmental analysis: Applied in monitoring environmental contaminants and
pollutants with high sensitivity.
9.3.3.9 Hybrid Analyzers
Hybrid analyzers in mass spectrometry combine two or more different types of mass
analyzers within a single instrument. This design allows for enhanced performance
394 9 Comprehensive Insights into Mass Spectrometry
by leveraging the strengths of each analyzer type while compensating for their
weaknesses. Hybrid systems can achieve high resolution, mass accuracy, and
improved sensitivity, making them ideal for complex analyses.
9.3.3.9.1 Types of Hybrid Analyzers
Quadrupole-time-of-flight (Q-TOF): Combines a quadrupole mass filter with a TOF
analyzer.
• Function: The quadrupole is used for selecting specific ions, which are then
analyzed by the TOF for high-resolution mass measurement.
• Applications: Ideal for proteomics, metabolomics , and small molecule analysis
due to its high sensitivity and accuracy.
Quadrupole-Orbitrap (Q-Orbit
rap): Integ rates
a quadrupole mass filter with an
Orbitrap mass analyzer.
• Function: The quadrupole selectively isolates ions before they enter the Orbitrap,
providing high resolution and mass accuracy.
• Applications: Frequently used in complex biological samples, drug disco very,
and environmental analysis.
Ion trap-TOF (IT-TOF): Combines
trap with a time-of-flight analyzer.
an ion
• Function: The ion trap allows for effective ion accumulation and fragmentation,
while the TOF provides rapid mass analysis.
• Applications: Suitable for detailed structural analysis and characterization of
biomolecules.
• Magnetic secto
r-TOF (MS-T
1. Description: Combines a magnetic sector mass analyzer with a
OF).
time-of-flight
analyzer.
2. Function: The
magnetic sector provides high resolution and mass accuracy,
while the TOF enables rapid analysis.
3. Applications: Used in applications requi
ring detai
led mass measurements and
fast analysis, such as in environmental and forensic studies.
9.3.3.9.2 Advantages
• Enhanced performance: Combining different analyzers allows for improved
resolution, sensitivity, and dynamic range.
• Versatility: Can
analyze a wider
variety of compounds, including small
molecules, peptides, and proteins.
• Fragmentation capabi
lities: Some hybrid systems allow for MS/MS experiments,
facilitating structural elucidation through fragmentation analysis.
9.3 Instrumentation 395
9.3.3.9.3 Limitations
• Complexity: The combination of different mass analyzers increases the complex-
ity of the instrument, requiring sophisticated calibration and data analysis.
• Cost: Hybrid analyzers tend to be more expensive than
both in terms of initial investment and maintenance.
9.3.3.9.4 Applications
• Proteomics: Hybrid analyzers are widely used for protein identification, charac-
terization, and quantification.
• Metabolomics: Ideal for profiling metabolites in biological samp
insights into
• Pharmaceutical development: Used in drug
date pharmacokinetic profiles and identify metabolites.
• Environmental monitoring: Effective
contaminants and pollutants.
metabolic changes and disease mechanisms.
metabolism
in detecting
single analyz
studies, helping to eluci-
trace levels of environmental
er systems,
les, providing
9.3.4 Detector
The detector measures the abundance of ions at specific m/z values. Common
detectors include electron multipliers and microchannel plates, which convert ion
signals into electrical signals.
9.3.4.1 TOF Detector
The TOF detector is a critical component in mass spectrometry that measures the
time taken by ions to travel a specific distance after being accelerated by an electric
field. This measurement allows for the determination of the m/z of the ions, which is
essential for analyzing the composition of the sample.
9.3.4.1.1 Operation Principle
• Ions generated in the ionization source are accelerated by a high voltage.
• The time it takes for the ions to travel from the source to the detector is measured.
• The flight time is proportional to the square root of the mass-to-charge ratio (m/z)
of the ions; lighter ions travel faster than heavier ions.
9.3.4.1.2 Components
• Ion source: Where the ions are generated (e.g., MALDI, ESI
• Acceleration
• Drift tube: A field-free region wher
• Detector: Records the arrival time of the ions.
9.3.4.1.3 Types of TOF Detectors
• Microchannel plate
amplifies the ion signal through secondary electron emission.
region: Ions are accelerated by an electric field.
e ions
travel to the detector.
(MCP): Commonly used in TOF mass spectrometers; it
).
396 9 Comprehensive Insights into Mass Spectrometry
• Faraday cup: Collects ions and measures the current to determine the abundance
of the ions, but is slower than MCP.
• Photomultiplier tube (PMT): Used in some TOF systems for detecting ion impact.
9.3.4.1.4 Advantages
• High resolution and mass accuracy, capable of distinguishing between ions with
small differences in mass.
• Rapid analysis of samples, allowing for high-throughput applications.
• Ability to analyze a wide mass range, from small molecules to large
biomolecules.
9.3.4.1.5 Applications
• Proteomics: Identifying and characterizing proteins and peptides.
• Small molecule analysis: Environmental testing, pharmaceuticals, and
metabolites.
• Polymer characterization: Analyzing the molecular weight distribution of
polymers.
9.3.4.2 Electron Multiplier
The electron multiplier (EM) is a sensitive detector commonly used in mass spectrometry to amplify the signal of ions. It operates by converting incoming ions into
electrons and subsequently amplifying these electrons to produce a measurable
current. This amplification allows for the detection of even low-abundance ions in
a sample.
9.3.4.2.1 Operation Principle
• When an ion strikes the surface of the electron multiplier, it can dislodge one or
more secondary electrons.
• These secondary electrons are then accelerated toward a series of dynodes
(electron amplification stages).
• Each dynode emits additional secondary electrons upon impact, creating a cascading effect that results in a significant amplification of the initial signal.
• The final output current is measured to determine the abundance of the
original ion.
9.3.4.2.2 Components
• Dynodes: A series of electrodes arranged in a specific geometry; each dy node is at
a progressively higher voltage to accelerate the secondary electrons.
• Collector: Collects the amplified
electrons and
converts them into a measurable
current.
• Anode: The final
component where
the collected current is sent for analysis.
9.3.4.2.3 Types of Electron Multipliers
• Continuous electron
multiplier (CEM): Provides a continuous signal and is
suitable for detecting ions at various intensities.
9.3 Instrumentation 397
• Channeltron: A type of EM that operates similarly to a continuous multiplier but
is constructed in a different geometry, typically providing better sensitivity and
resolution.
• Microchannel plate (MCP): A specialized form of EM that consists of many tiny
channels, allowing for rapid electron amplification and high detection rates.
9.3.4.2.4 Advantages
• High sensitivity, capable of detecting low ion concentrations.
• Fast response time, allowing for real-time analysis of rapidly changing ion
populations.
• Wide dynamic range, suitable for both low and high abundance ions.
9.3.4.2.5 Applications
• Mass spectrometry: Used as a detector in various mass analyzers, including timeof-flight (TOF) and quadrupole mass spectrometers.
• Surface analysis: Employed in secondary ion mass spectrometry (SIMS) to
analyze surfaces and thin films.
• Environmental monitoring: Used for detecting trace levels of pollutants and
contaminants.
9.3.4.3 Microchannel Plate Detector
The microchannel plate (MCP) detector is a highly sensitive device used in mass
spectrometry and other applications for the detection and amplification of ions. It
operates on the principle of secondary electron emission and offers remarkable
performance in terms of sensitivity, speed, and spatial resolution.
9.3.4.3.1 Operation Principle
• The MCP consists of a plate made up of many parallel microchannels, typically
ranging from 5 to 25 micrometers in diameter.
• When an ion enters a microchannel, it collides with the walls, causing the
emission of seconda ry electrons.
• These secondary electrons are then accelerated through the channels, leading to
further collisions and the emission of more electrons.
• This cascading effect results in a significant amplification of the original ion
signal, creating a large number of electrons that can be collected for measurement.
9.3.4.3.2 Structure
• Microchannels: The core component of the MCP, arranged in a close-packed
array to maximize detection efficiency.
• Input and output faces: The input face is where ions enter, while the output face
collects the amplified electron signal.
• Voltage biasing: The
channels are biased with a high voltage to facilitate the
acceleration of electrons and enhance amplification.
398 9 Comprehensive Insights into Mass Spectrometry
9.3.4.3.3 Advantages
• High sensitivity: MCP detectors can detect very low levels of ions, making them
ideal for applications requiring high sensitivity.
• Fast response time: MCPs can respond quickly to incoming ions, allowing for
real-time analysis and high-speed measurements.
• Excellent spatial resolution: The small diameter of the microchannels allows for
precise localization of ion impacts, making MCPs suitable for imaging
applications.
9.3.4.3.4 Types of MCP Detectors
• Standard MCPs: Used for general mass spectrometry applications.
• Position-sensitive MCPs: Equipped with an additional readout system to provide
spatial information about the incoming ions.
• Stacked MCPs: Multiple MCPs stacked together to enhance gain and perfor-
mance further.
9.3.4.3.5 Applications
• Mass spectrometry: Widely used in time-of-flight (TOF) mass spectrometers and
other mass analysis techniques for detecting ions.
• Imaging mass spectrometry: Employed in techniques that require spatial resolu-
tion to map the distribution of compounds in biological samples or materials.
• Astrophysics and space science: Utilized in space instruments for detecting
cosmic particles and analyzing planetary surfaces.
9.3.4.4 Photomultiplier Tube
A photomultiplier tube (PMT) is a highly sensitive light detector that converts
incident photons into an electrical signal. It is commonly used in mass spectrometry
and other applications requiring the detection of low levels of light. The PMT
operates on the principle of the photoelectric effect and electron multiplication,
allowing for the amplification of weak signals.
9.3.4.4.1 Operation Principle
• Photoelectric effect: When light (photons) strikes the photocathode of the PMT, it
causes the emission of photoelectrons.
• Electron multiplication: The emitted photoelectrons are accelerated toward a
series of dynodes, which are electrodes held at progressiv ely higher voltages.
Each time an electron strikes a dynode, additional electrons are released through
secondary emission, resulting in an avalanche of electrons.
• Signal output: The amplified electron signal is collected at the anode, generating a
measurable electrical current proportional to the number of incident photons.
9.3.4.4.2 Structure
• Photocathode: The surfac
e that absorbs incoming photons and emits
photoelectrons.
9.3 Instrumentation 399
• Dynodes: A series of electrodes where electron multiplication occurs; typically,
there are 10–14 dynodes in a PMT.
• Anode: The final electrode where the multiplied signal is collected and output as
an electrical current.
9.3.4.4.3 Advantages
• High sensitivity: PMTs can detect
single photons,
making them ideal for low-light
applications.
• Wide dynamic range: PMTs can measure a wide range of light intensities, from
very low to very high.
• Fast response time: PMTs can respond quickly to changes in light intensity,
enabling real-time measurements.
9.3.4.4.4 Types of PMTs
• Standard PMTs: Used for general applications requiring light detection and
amplification.
• Photon counting PMTs: Specifically desig
ned for
detecting single photons and
very low light levels.
• Multi-anode PMTs: Equipped with multiple anodes to allow for position-
sensitive detection
and ima
ging applications.
9.3.4.4.5 Applications
• Mass spectrometry: Used as a detector in mass spectrometers, particularly in
combination with ionization techniques that produce light (e.g., MALDI).
• Nuclear and particle physics: Employed in experi ments to detect scintillation
light from radioactive decay or particle interactions.
• Medical imaging: Used in positron emission tomography (PET) and other imag-
ing techniques to detect gamma rays.
9.3.4.5 Ion Trap Detector
An ion trap detector is a device used in mass spectrometry to confine ions in a small
space using electric or magnetic fields. It enables the analysis of ions based on their
m/z ratio and is particula rly effective for capturing and analyzing ions in a controlled
environment. Ion trap detectors are versatile and can be used in various
configurations, including quadrupole ion traps and ion cyclotron resonance traps.
9.3.4.5.1 Operation Principle
• Ion confinement: Ions are trapped within a specific region using oscillating
electric fields (in the case of a quadrupole trap) or static electric and magnetic
fields (in the case of an ion cyclotron resonance trap).
• Selective ejection: The trapped
ions can be selectively ejected based on their m/z
ratios by varying the parameters of the electric or magnetic fields, allowi ng for the
analysis of specific ions.
400 9 Comprehensive Insights into Mass Spectrometry
• Detection: Once the ions are ejected, they can be detected by a secondary
detector, such as a PMT or an electron multiplier, which converts the ion signal
into a measurable electrical signal.
9.3.4.5.2 Types of Ion Traps
• Quadrupol e ion trap (QIT): Utilizes a combination of radiofrequency (RF) and
direct current (DC) voltages to trap ions. It can perform tandem mass spectrometry (MS/MS) experi ments effectively.
• Ion cyclotron resonance (ICR) trap: Uses a strong magnetic field to trap ions in a
circular motion, allowing for high-resolution mass analysis. It is often coupled
with Fourier transform (FT) detection for enhanced sensitivity and resolution.
9.3.4.5.3 Advantages
• High sensitivity: Ion traps are sensitive detectors capable of detecting
low-abundance ions due to their efficient ion confinement.
• MS/MS capabilities: Ion traps allow for fragmentation of selected ions,
facilitating structural analysis and identification of compounds.
• Compact design: The compact nature of ion traps makes them suitable for
portable mass spectrometers and miniaturized analytical instruments.
9.3.4.5.4 Applications
• Proteomics and metabolomics: Used for the analysis of complex biological
samples to identify proteins, metabolites, and other biomolecules.
• Environmental analysis: Employed in the detection of trace pollutants and
contaminants in environmental samples.
• Pharmaceutical analysis: Utilized for drug development and
the
identification of drug metabolites and impurities.
testing, including
9.3.4.5.5 Limitations
• Mass range: Ion traps typically have a limited mass range compared to other mass
analyzers, which can restrict their application to specific types of analytes.
• Dynamic range: Although they are
sensitive,
ion traps may exhibit nonlinear
responses for high-abundance ions due to space charge effects.
9.3.4.6 Array Detectors
Array detectors are advanced detection systems used in mass spectrometry and other
analytical techniques. They consist of multiple detection elements arranged in an
array format, allowing simultaneous measurement of multiple signals. This configuration enhances the speed and sensitivity of analysis, making it a valuable tool in
various applications.
9.3.4.6.1 Operation Principle
• Simultaneous detection: Array
detectors can detect multiple ions or signals at
once by employing a matrix of sensing elements, such as photodiodes or other
types of detectors.