This document summarizes the principles and components of liquid chromatography-mass spectrometry (LC-MS). LC-MS combines liquid chromatography with mass spectrometry to separate and analyze compounds. Key components discussed include the liquid chromatograph, which separates compounds using a mobile and stationary phase; the mass spectrometer, which ionizes the separated compounds and measures their mass-to-charge ratios; and the interface between the two, which introduces the separated compounds into the mass spectrometer. Common ionization sources, mass analyzers, detectors, and data recording methods used in LC-MS are also described.
• It is the combination of liquid chromatography and the mass spectrometry.
• Liquid chromatography-mass spectrometry (LC-MS) is an analytical chemistry
technique that combines the physical separation capabilities of liquid
chromatography with the mass analysis capabilities of mass spectrometry.
• The combination of these two powerful techniques gives the chemical analyst the
ability to analyze virtually any molecular species; including, thermally labile, non
volatile, and high molecular weight species.
Mass Spectrometry (MS) is an analytic technique used to determine the relative masses of molecular ions and fragments by calculating the degree of deflection of charged particles in a magnetic field.
It provides a great deal of information with very small amount of samples.
Electron Spray Ionization (ESI) and its ApplicationsNisar Ali
In this slide ,You will get to learn Electron Spray Ionization (ESI) technique used in Mass Spectroscopy and its Various Application in Pharmaceutical Drug Analysis.
• It is the combination of liquid chromatography and the mass spectrometry.
• Liquid chromatography-mass spectrometry (LC-MS) is an analytical chemistry
technique that combines the physical separation capabilities of liquid
chromatography with the mass analysis capabilities of mass spectrometry.
• The combination of these two powerful techniques gives the chemical analyst the
ability to analyze virtually any molecular species; including, thermally labile, non
volatile, and high molecular weight species.
Mass Spectrometry (MS) is an analytic technique used to determine the relative masses of molecular ions and fragments by calculating the degree of deflection of charged particles in a magnetic field.
It provides a great deal of information with very small amount of samples.
Electron Spray Ionization (ESI) and its ApplicationsNisar Ali
In this slide ,You will get to learn Electron Spray Ionization (ESI) technique used in Mass Spectroscopy and its Various Application in Pharmaceutical Drug Analysis.
introduction and principle of Mass spectrometry with its components.
ionization , accelerators deflection and detection, types of MS, different types of ion sources , types of mass analyzers , advantages and disadvantages of different types of ion source and mass analyzers, different types of detectors for the ions dectections
various parts of mAss spectroscopy, applications, principle, peaks, rules, typical mass spectra, various combinations, Fragmentation, rules of fragmentation and useful points which can help Chemical and analytical students and structural elucidation.
introduction and principle of Mass spectrometry with its components.
ionization , accelerators deflection and detection, types of MS, different types of ion sources , types of mass analyzers , advantages and disadvantages of different types of ion source and mass analyzers, different types of detectors for the ions dectections
various parts of mAss spectroscopy, applications, principle, peaks, rules, typical mass spectra, various combinations, Fragmentation, rules of fragmentation and useful points which can help Chemical and analytical students and structural elucidation.
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
Anti ulcer drugs and their Advance pharmacology ||
Anti-ulcer drugs are medications used to prevent and treat ulcers in the stomach and upper part of the small intestine (duodenal ulcers). These ulcers are often caused by an imbalance between stomach acid and the mucosal lining, which protects the stomach lining.
||Scope: Overview of various classes of anti-ulcer drugs, their mechanisms of action, indications, side effects, and clinical considerations.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Pulmonary Thromboembolism - etilogy, types, medical- Surgical and nursing man...VarunMahajani
Disruption of blood supply to lung alveoli due to blockage of one or more pulmonary blood vessels is called as Pulmonary thromboembolism. In this presentation we will discuss its causes, types and its management in depth.
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
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The principle and performance of liquid chromatography–mass spectrometry (LC-MS)
1. 1
The principle and performance of liquid chromatography–mass spectrometry
(LC-MS)
Ljubica Glavaš-Obrovac
Introduction
Chromatography is a separation technique used to separate the individual compound from
a mixture using a stationary and mobile phase. Chromatographic separation is based on the
principles of chirality, ion exchange, molecular exclusion, affinity, adsorption and partition.
According to the state of the mobile phase, chromatography can be divided into gas
chromatography, liquid chromatography, and supercritical fluid chromatography. According to
the geometric forms of the stationary phase, chromatography can be divided into column
chromatography and planar chromatography (paper chromatography and thin layer
chromatography).
Combination of chromatography with spectrometry is first reported in 1967 and first
liquid chromatography–mass spectrometry (LC-MS) system was introduced in 1980s. LC-MS is
an analytical chemistry technique that combines the physical separation capabilities of liquid
chromatography with the mass analysis and mass spectrometry. LC-MS is now a routine
technique providing a simple and robust interface to determine a wide range of compounds in
biological samples in the research and clinical laboratory setting1
. Fast scanning speeds allow a
high degree of multiplexing and many compounds can be measured in a single analytical run
(Slide 2).
Liquid chromatography–mass spectrometry (LC-MS) system
The components of LC-MS are a liquid chromatograph (LC) and mass spectrometer (MS) that
are interconnected by interface, which has a multiple role: liquid release, neutralization of neutral
molecules and introduction of analytes into the analyzer (Slide 3). Cross-flow transitions
occurring in the intermediate are vaporization and desorption2
.
Liquid chromatography (LC)
The most commonly used liquid chromatography (LC) method is column chromatography
which regards liquid as a mobile phase. A basic LC system consists of (a) a solvent inlet filter,
(b) pump, (c) inline solvent filter, (d) injection valve, (e) pre-column filter, (f) column, (g)
detector, (h) recorder, (i) backpressure regulator, and (j) waste reservoir. As shown (Slide 4), the
solvent inlet brings in the mobile phase which is then pumped through the inline solvent filter and
passed through the injection valve. This is where the sample is introduced in the mobile phase
flow path. It then gets passed through another filter and then passed through the column where
the sample will be separated into its components. The detector detects the separation of the
analytes and the recorder, usually a computer, will record this information. The sample then goes
2. 2
through a backpressure filter and into waste. LC has a great advantage on the capability of
separating complex samples, so it is the most effective option when mixtures separation is
needed, but is not suitable to obtain structural information of the material3
. High performance
liquid chromatography (HPLC) is modified based on the classical LC. It is a form of column
chromatography that pumps analyte in a mobile phase at a high pressure through the column with
chromatographic packing material (stationary phase). HPLC has the ability to separate, and
identify compounds, that are present in any sample that can be dissolved in a liquid in trace
concentrations as low as parts per trillion. These separations are useful in the proteomics area
where high sensitivity and resolution are required to identify as many components as possible1-3
.
Mass spectrometry (MS)
Mass spectrometry is an analytical technique widely used to quantify known materials, to
identify unknown compounds within a sample, and to elucidate the structure and chemical
properties of different molecules. MS is widely used due to its high selectivity, high sensitivity,
and capability of providing information including relative molecular mass and structural
characteristics. This technique basically studies the effect of ionizing energy on molecules4
.
Mass Spectrometry Instrumentation
Mass spectrometers operate by converting the analyte to a charged (ionized) state, with
subsequent analysis of the ions and any fragment ions that are produced during the ionization
process, on the basis of their mass to charge ratio (m/z) (Slide 5). Several different technologies
are available for both ionization and ion analysis, resulting in many different types of mass
spectrometers with different combinations of these two processes. Schematic view of basic
components of mass spectrometer is shown on Slide 6.
The mass spectrometer consists of:
1. Sample Injection Unit: To introduce the samples to be studied to the ion source
2. Ion generation unit or Ionization Source: For producing ions from the tested analyte.
3. Mass Analyzer: For resolving the ions into their characteristics mass components
according to their mass-to-charge ratio.
4. Detector System: For detecting the ions and recording the relative abundance of each of
the resolved ionic species.
5. Data System: To control the instrument, acquire and manipulate data, and compare
spectra to reference libraries.
For the proper MS function, the mass analyzer, and the mass detector must be kept under a high
vacuum condition of 3×10-4
to 1.3 ×10-5
Pa. This high vacuum in spectrometer requires two
pumping stages. The first stage is a mechanical pump which provides rough vacuum down to
1x10-1
Pa and the second stage uses turbo molecular pumps or diffusion pumps to provide desired
high vacuum.
3. 3
Ion Sources
Current ion sources are capable of handling a wide range of flow rates and mobile phase
compositions so existing LC separations can often be directly coupled to the mass spectrometer.
The most widely used ion sources (Slide 7) are:
a. Electrospray Ionization (ESI)
b. Atmospheric Pressure Chemical Ionization Source (APCI)
c. Atmospheric Pressure Photo-Ionization (APPI)
d. Thermospray Ionization (TSI)
e. Particle Beam Ionization (PBI)
a. Electrospray Ionization (ESI) is one of the most widely used ionization methods in an LC-MS
system that is fully compatible with analyzer5
(Slide 8). While standard electrospray ionization
sources in mass spectrometer can generally handle flow rates up to 1 mL/min lower flow rates
result in improved sensitivity. ESI is considered a “soft” ionization source, meaning that
relatively little energy is imparted to the analyte, and hence little fragmentation occurs. ESI uses
electrical energy to assist the transfer of ions from solution into the gaseous phase before they are
subjected to mass spectrometric analysis. The use of a nebulizing gas (e.g. nitrogen), which
shears around the eluted sample solution, enhances a higher sample flow rate. In ESI an analyte is
introduced to the source at flow rates as low as 1 µl min-1
. As shown in the Slide 8 the analyte
solution flow passes through the electrospray needle that has a high potential difference with
respect to the counter electrode, typically in the range from 1 to 6 kV. With the aid of an elevated
ESI-source temperature and/or another stream of nitrogen drying gas, the charged droplets are
continuously reduced in size by evaporation of the solvent, leading to an increase of surface
charge density and a decrease of the droplet radius. As the droplets traverse the space between the
needle tip and the cone, solvent evaporation occurs and the droplet shrinks until it reaches the
point that the surface tension can no longer sustain the charge (the Rayleigh limit) at which point
a Coulombic explosion occurs and the droplet is ripped apart. Finally, the electric field strength
within the charged droplet reaches a critical point at which it is kinetically and energetically
possible for ions at the surface of the droplets to be ejected into the gaseous phase. The emitted
ions are sampled by a sampling skimmer cone and are then accelerated into the mass analyzer for
subsequent analysis of molecular mass and measurement of ion intensity.
With ESI-MS is possible to analyze moderately polar molecules and is well suited to the
analysis of many metabolites, xenobiotics and peptides. Although neutral and low polarity
molecules such as lipids can also be converted to ionic form in solution or in gaseous phase by
protonation or cationization (e.g. metal cationization) can be studied by ESI-MS, this may not be
efficiently ionized by this method1-3
.
b. Atmospheric Pressure Chemical Ionization Source (APCI). In APCI, as with ESI, liquid is
pumped through a capillary and nebulized at the tip (Slide 9). A corona discharge takes place
near the tip of the capillary, initially ionizing gas and solvent molecules present in the ion
source1-3
. These ions then react with the analyte and ionize it via charge transfer. This technique
4. 4
is useful for small, thermally stable molecules that are not well ionized by ESI such free steroid,
lipids and fat soluble vitamins6, 7
.
c. Atmospheric Pressure Photo-Ionization (APPI) uses photons to excite and ionize molecules
after nebulization (Slide 9). The energy of the photons is chosen to minimize concurrent
ionization of solvents and ion source gases. The technique also gives predominantly singly-
charged ions and has been used for the analysis of neutral compounds such as steroids6,8
.
d. Thermospray Ionization (TSI) is a rapid, highly specific and sensitive combined high
performance liquid LC-MS method in which a liquid is flowed through a heated capillary to
produce a spray of droplets and solvent vapor (Slide 10). Ions are formed due to the imbalance of
charges in the droplets or by a heated filament1-4
.
e. Particle Beam Ionization (PBI) is a LC-MS method in which the effluent is passed through a
heated capillary to form an expanding jet of vapor and aerosol particles. After passing through a
skimmer that acts as a momentum separator, the beam impinges on a heated surface to form ions
through chemical ionization at the surface or ionization of the resulting vapor in a chemical
ionization or electron ionization source (Slide 11). Electron impact ionization following gas
chromatography or particle beam introduction typically generates very reproducible, library-
searchable mass spectra1-4
.
Mass Analyzers1-7
Most commonly used mass analyzers (Slide 12) are:
a. Quadrupole analyzer
b. The time-of-flight (TOF) analyzer
c. Ion trap analyzers
d. Hybrid analyzers
Quadrupole analyzer consists of a set of four parallel metal rods. A combination of constant and
varying (radio frequency) voltages allows the transmission of a narrow band of m/z values along
the axis of the rods (Slide 13). By varying the voltages with time it is possible to scan across a
range of m/z values, resulting in a mass spectrum. Most quadrupole analyzers operate at more
than 4000 m/z and scan speeds up to 1000 m/z per sec or more. They usually operate at unit mass
resolution meaning that the mass accuracy is seldom better than 0.1 m/z. As an alternative to
scanning, the quadrupoles can be set to monitor a specific m/z value. This technique is useful in
improving the detection limits of targeted analytes because more detector time can be devoted to
detecting specific ions instead of scanning across ions that are not produced by the analyte.
Stepping can be carried out in a few milliseconds and a panel of m/z values can be stepped
through for the detection of several analytes. Ions can be induced to undergo fragmentation by
5. 5
collisions with an inert gas such as nitrogen or argon, by a process called collision induced
dissociation. One type of collision cell is a quadrupole that has been designed to maintain the low
pressure of the collision gas required for dissociation and transmit most of the fragment ions that
are produced. A particularly useful mass spectrometer configuration is obtained by placing a
collision cell between two quadrupole mass analyzers. This combination is called a triple
quadrupole mass spectrometer and is an example of tandem MS in which two or more stages of
mass analysis are independently applied. Quadrupole analyzers, either in the single or triple
quadrupole configuration, are widely used in clinical LC-MS applications owing to the ease of
scanning and the good quality quantitative data obtained.
b. The time-of-flight (TOF) analyzer operates by accelerating ions through a high voltage (Slide
14). The velocity of the ions, and hence the time taken to travel down a flight tube to reach the
detector, depends on their m/z values. If the initial accelerating voltage is pulsed, the output of the
detector as a function of time can be converted into a mass spectrum. The TOF analyzer can
acquire spectra extremely quickly with high sensitivity. It also has high mass accuracy, which
allows molecular formulas to be determined for small molecules.
c. Ion trap analyzers use three hyperbolic electrodes to trap ions in a three-dimensional space
using static and radio frequency voltages (Slide 14). Ions are then sequentially ejected from the
trap on the basis of their m/z values to create a mass spectrum. Alternatively, a specific ion can be
isolated in the trap by the application of an exciting voltage while other ions are ejected. An inert
gas can also be introduced into the trap to induce fragmentation. An interesting feature of these
ion trap analyzers is the ability to fragment and isolate ions several times in succession before the
final mass spectrum is obtained, resulting in so-called MSn
capabilities.
d. Hybrid analyzers. Tandem mass spectrometers that use combinations of different mass
analyzers are useful for LC-MS. The third quadrupole of a triple quadrupole MS can be replaced
by a TOF analyzer to produce a hybrid quadrupole time-of-flight (QTOF) mass spectrometer.
QTOF instruments have been used extensively in the proteomics field but are more limited in
their scanning functions than triple quadrupole instruments. It is also possible to design
instruments in which the third quadrupole of a triple quadrupole MS operates in a different mode
in which ions are trapped and then sequentially ejected on the basis of their m/z values. This is
known as a linear ion trap and the overall configuration is often referred to as a QTrap
instrument. The end quadrupole can be switched between ion trap mode and conventional
quadrupole mode so the instrument combines useful features of both triple quadrupole and ion
trap analyzers. When used in ion trap mode, sensitivity in product ion scanning is considerably
enhanced, and additional fragmentation can be induced within the ion trap allowing an additional
stage of fragmentation and mass analysis.
6. 6
Detectors1-7
When ions are separated by a mass analyzer it is necessary to qualitatively and
quantitatively determine them. Detection is most commonly performed electrically, by taking
abundance - the total ionic current, and some type of electron multiplier is frequently used (Slide
15). The Faraday cup is more an ion collector than detector (Slide 16). It collect entered ions and
transfers their charge to the cup. Charge is usually transferred to electronics outside the vacuum
system. Type of electronics determines whether measured as charge, current or voltage. The
Faraday cup seems simple but in practice becomes quite complicated. The first and major
complication is that the ions entering have energies significantly higher than the work function of
the cup material (stainless steel, carbon, graphite) what cause the generation of free electrons,
known as secondary electrons.
When small power abundances (10-9
-10-6
A) are needed, various single-cell electric
amplifiers (DC-Amplifiers), photomultiplier conversion dynodes, electron multiplier, and
vibrating reed electrometer are used.
The principle of the electron multiplier function is based on the use of several
consecutive dynodes with a growing potential (Slide 17). Ionic air from the mass analyzer falls
on the multiplier electrode and sparks electrons, usually one to two electrons per ion. They are
accelerated on the way to the next Faraday cup which has higher potential than the previous one,
so that even more electrons are emitted and so in the order of 8 to 20 times. In this way, the input
signal strengthens up to 1012
times, which is why it has a high sensitivity. The highest
susceptibility is achieved at a voltage of about 3000 V, but such a high voltage shortens the life of
the detector.
In the photomultiplier (Slide 18), ions are emitted from a mass analyzer, translated into photons,
and detect. This device has a lower sensitivity, but it is much longer lasting.
Data Recording1-7
Multiple reactions monitoring by computers is commonly used in LC-MS assays. Data collecting
during MS analysis (Slide 19) can be performed by:
1. Capturing a complete mass spectrum - SCAN technique
2. Selected ion monitoring - SIM technique
3. Probability Based Matching system
1. SCAN technique
SCAN technique implies mass scanning in the given range while simultaneously
monitoring the retention time which allows identification of the analyte. The default volume
range and the chromatographic scan rate determine the duration of the dwell time. During each
cycle, each mass of the given range is recorded only once, and the cycles are repeated during
chromatography. The total chromatogram of ions represents the graph of the dependence of the
7. 7
total abundances collected during the analysis, from time to time. The data are obtained on the
quality (time retention) and the quantity (peak area), and by constant length chromatography as
well. On the basis of these data, ionic chromatogram can be displayed. By its use, the selectivity
of peaks that overlaps to a great extent is increased, if the characteristic properties of the
overlapped components are different. Scanning is usually performed at a speed of 0.5 to 1 scan/s.
SCAN technique is used more in qualitative analysis.
2. SIM technique
It is used in quantitative analysis. Prior to its use, in order to achieve optimal conditions,
analysis must be performed by the SCAN method. The SIM technique detects the values of m/z
only of the representative ions of the observed molecule. Tracking time is bigger, so it increases
the sensitivity even 100 to 1000 times. Characteristic junctions start time, and dwell times as well
are selected based on the data obtained through the SCAN technique. The chromatogram is
obtained as a dependence on the total abundance collected during the time analysis, and gives
data on the quality (retention time) and the quantity (point surface) of the observed compounds.
Each point in the chromatogram represents a sum of abundances of observed ions. SIM
techniques can also be used for qualitative determination of trace components.
3. Probability Based Matching system
It is very useful in compounds identification because it identifies the component by
dividing the spectra in the existing database with an unknown spectrum of the test compound.
McLafferety's algorithm-based probability-based evaluation method has been used to identify a
component. This system applies a retrieval method, so the entire content of the library can be
compared to an unknown spectrum. When choosing the most significant peaks of the reference
mass spectrum, both mass and abundance are equally valued. Reverse search determines whether
peaks in the reference mass spectrum are present in the spectrum of the test substance. If an
excess of peaks appears in the examined spectrum, they are ignored so that the mass spectra of
the analyte mixture and the impurities present can be analyzed. In most other systems, the mass
spectrum of an unknown compound is compared with already known spectra.
Most MS instruments have the capability of data-dependent acquisition, meaning that it is
possible to switch between the different modes of operation within a run based on the results that
are being acquired. The computer also captures spectra, primarily processes them, recognizes and
performs computations related to the application of MS. In addition to the MS data, the computer
requires data from other analytical procedures, from documentation as well, and commercial and
proprietary data libraries too.
Applications9,10,11, 12, 13, 14
Mass spectrometry using electrospray ionization and other ionization methods as well,
can be applied to a much wide range of biological molecules and will thus find greater
8. 8
application in the laboratory medicine (Slide 20). Direct injection methods can determine many
analytes with high through-put when highly specific tandem MS is used for detection. LC-MS
provides superior specificity and sensitivity compared to direct injection methods. When
combined with stable isotope dilution, LC-MS can be used to develop highly accurate and
reproducible assays. Modern mass spectrometers are highly sensitive and LC-MS assays are in
the use for pharmaceutical analysis, bioavailability studies, drug metabolism studies,
pharmacokinetics, characterization of potential drugs, drug degradation product analysis,
screening of drug candidates, identifying drug targets, biomolecule characterization, proteins,
peptides and oligonucleotides analyses, environmental analysis such as determination of
pesticides on foods, soil and groundwater contamination, and forensic analysis as well.
References
1
Watson, J.T., Sparkman, O.D. Introduction to Mass Spectrometry: Instrumentation,
Applications and Strategies for Data Interpretation, 4th
Edition, John Wiley & Sons, Ltd, pp173,
(2007).
2
Parasuraman, S. Rao, A., Balamurugan, S., Muralidharan, S., Kumar, K., Venugopal, V. An
overview of liquid chromatography-mass spectroscopy instrumentation. Pharmaceutical
Methods. 5, 47-55 (2014).
3
Pitt, J.J. Principles and applications of liquid chromatography-mass spectrometry in clinical
biochemistry. Clin Biochem Rev. 30 (1), 19-34, (2009).
4
Demartini, D.R. A Short Overview of the Components in Mass Spectrometry Instrumentation
for Proteomics Analyses. In Tandem Mass Spectrometry - Molecular Characterization. (Ed. A. V.
Coelho and C. de Matos Ferraz Franco), ISBN 978-953-51-1136-8, Chapter 2 (Open access) (
2013)
5
Chan, M.H., Cheung, R.C., Law, L.K, Lit, L.C., Ng K.F., Suen, M.W., Tai, H.L. Electrospray
ionisation mass spectrometry: principles and clinical applications. Clin Biochem Rev. 24, 3-12
(2003).
6
Woźniak, B., Matraszek-Żuchowska, I., Witek, S., Posyniak, A. Development of LC-MS/MS
confirmatory method for the determination of testosterone in bovine serum. J Vet Res 61, 81-89,
(2017).
7
Keevil, B.G. LC-MS/MS analysis of steroids in the clinical laboratory. Clin Biochem. 49 (13-
14), 989-97. (2016), doi: 10.1016/j.clinbiochem.
8
Kauhanen, D., Sysi-Aho, M., Koistinen, K.M., Laaksonen, R., Sinisalo, J., Ekroos, K.
Development and validation of a high-throughput LC–MS/MS assay for routine measurement of
molecular ceramides. Analytical and Bioanalytical Chemistry. 408 (13), 3475–3483. (2016).
9
Rekhi, H., Rani, S., Sharma, N., Malik, A.K. A Review on Recent Applications of High-
Performance Liquid Chromatography in Metal Determination and Speciation Analysis. Crit Rev
Anal Chem. 2;47, 524-537. (2017) doi: 10.1080/10408347.2017.1343659.
9. 9
10
Kadhi,O.A., Melchini,A., Mithen,R., SahaS. Development of a LC-MS/MS Method for the
Simultaneous Detection of Tricarboxylic Acid Cycle Intermediates in a Range of Biological
Matrices. J Analyt Meth Chem. (2017). https://doi.org/10.1155/2017/5391832
11
Melanson, S.E., Ptolemy, A.S., Wasan, A.D. Optimizing urine drug testing for monitoring
medication compliance in pain management. Pain Med 14, 1813–20 (2013).
12
Shah, P.A., Sharma, P., Shah, J.V., Sanyal, M., Shrivastav, P.S. An improved LC-MS/MS
method for the simultaneous determination of pyrazinamide, pyrazinoic acid and 5-hydroxy
pyrazinoic acid in human plasma for a pharmacokinetic study. J Chromatogr B Analyt Technol
Biomed Life Sci. 1017-1018, 52-61, (2016) doi: 10.1016/j.jchromb.2016.02.036.
13
Pohanka, A., Rosenborg, S., Lindh, J.D., Beck, O . Experiences from using LC-MS/MS for
analysis of immunosuppressive drugs in a TDM service. Clin Biochem. 49 (13-14), 1024-31,
(2016) doi: 10.1016/j.clinbiochem.2016.06.013.
14
Wan, D., Yang, J., Barnych, B., Hwang, S.H. et al. A new sensitive LC/MS/MS analysis of
vitamin D metabolites using a click derivatization reagent, 2-nitrosopyridine. J Lipid Res. doi:
10.1194/jlr.D073536 (2017)