Mass spectroscopy is an analytical technique used to measure the mass-to-charge ratio (m/z) of one or more molecules present in a sample. It can be used to identify unknown compounds via molecular weight determination, quantify known compounds, and determine the structure and chemical properties of molecules.2 Mass spectroscopy is also useful for studies on protein-protein interactions. The basic principle involves fragmentation of a compound or molecule into charged species, which are accelerated, deflected, and finally focused on a detector according to their mass and charge ratio.Mass spectroscopy is an instrumental method for identifying the chemical constitution of a substance by means of the separation of gaseous ions according to their differing mass and charge.
Mass spectrometry is a technique that analyzes molecules by generating ionized molecules and measuring their mass-to-charge ratios. A mass spectrometer bombards neutral molecules with electrons, producing molecular ions and fragments that are separated by their mass-to-charge ratios and detected. The resulting mass spectrum plots the relative abundances of ions versus mass-to-charge ratios and provides information about molecular weight, structure, and isotopic composition. Interpreting mass spectra involves identifying peaks corresponding to molecular ions and common isotopes to deduce the molecular formula.
Mass spectrometry breaks molecules into fragments using high-energy electrons. The masses of the fragments and their relative abundances provide information about molecular weight, structure, and functional groups. Key principles for interpreting mass spectra include identifying the parent ion peak from molecular weight, observing isotope effects, and examining fragmentation patterns according to the nitrogen rule and common losses of simple groups like methyl or ethyl.
Introduction, Basic Principles, Terminology, Instrumentation, Ionization techniques (EI, CI, FAB, MALDI, and ESI), Mass Analyzer (Magnetic sector instruments, Quadrupole, TOF, and ICR ), and Applications of Mass Spectrometry.
Mass spectrometry(Ionization Techniques) by Ashutosh PankeAshutosh Panke
The document discusses various ionization techniques used in mass spectrometry. It describes several gas phase ionization methods including electron impact ionization, chemical ionization, and field ionization. It also discusses several desorption ionization techniques, notably fast atom bombardment, matrix assisted laser desorption/ionization, electrospray ionization, and surface enhanced laser desorption/ionization. The document provides details on the mechanisms and applications of these various ionization methods. It also categorizes mass analyzers and discusses time-of-flight mass analyzers.
Mass spectrometry involves ionizing molecule samples and then measuring their mass-to-charge ratios. The samples are bombarded with electrons to produce molecular ions, which then fragment into product ions. These ions are separated based on their mass-to-charge ratios and detected, producing a mass spectrum that shows the abundances of each ion. This spectrum provides structural information about the precursor molecule and can be used to identify unknown compounds. Mass spectrometry is widely applied across many scientific fields including pharmaceutical analysis, environmental testing, and forensics.
This document provides an overview of the key components and operating principles of mass spectrometry. It discusses the inlet system, ion sources, mass analyzers, detectors, and vacuum system. Common types of ion sources like electron impact and chemical ionization are described. Popular mass analyzers such as quadrupole, time-of-flight, ion trap, and double focusing are explained. The document also covers the theory behind how mass spectrometry separates ions based on their mass-to-charge ratio and discusses the need for high vacuum levels in mass spectrometers.
The document discusses UV-visible spectroscopy, which involves measuring the absorption of ultraviolet or visible radiation by molecules as they transition between energy levels. It explains the basic concepts of spectroscopy including electromagnetic radiation, absorption curves, electronic transitions, and Beer's and Lambert's laws which describe the relationship between absorbance and analyte concentration. The principles of UV-visible spectroscopy are useful for qualitative and quantitative analysis of compounds in various applications.
The document discusses mass spectrometry and provides information on various topics related to it including:
- Types of ions produced including molecular ions, fragment ions, and metastable ions.
- Common fragmentation patterns for different functional groups such as alkanes losing alkyl groups, alkenes forming allylic ions, and aromatics fragmenting at benzylic carbons.
- General rules for fragmentation including favored cleavage at branched points and loss of the largest substituent from a branch.
- Examples of mass spectra and prominent peaks are shown for compounds like ethanol, 2-pentanone, and hydrocinnamaldehyde to illustrate fragmentation patterns.
Mass spectrometry is a technique that analyzes molecules by generating ionized molecules and measuring their mass-to-charge ratios. A mass spectrometer bombards neutral molecules with electrons, producing molecular ions and fragments that are separated by their mass-to-charge ratios and detected. The resulting mass spectrum plots the relative abundances of ions versus mass-to-charge ratios and provides information about molecular weight, structure, and isotopic composition. Interpreting mass spectra involves identifying peaks corresponding to molecular ions and common isotopes to deduce the molecular formula.
Mass spectrometry breaks molecules into fragments using high-energy electrons. The masses of the fragments and their relative abundances provide information about molecular weight, structure, and functional groups. Key principles for interpreting mass spectra include identifying the parent ion peak from molecular weight, observing isotope effects, and examining fragmentation patterns according to the nitrogen rule and common losses of simple groups like methyl or ethyl.
Introduction, Basic Principles, Terminology, Instrumentation, Ionization techniques (EI, CI, FAB, MALDI, and ESI), Mass Analyzer (Magnetic sector instruments, Quadrupole, TOF, and ICR ), and Applications of Mass Spectrometry.
Mass spectrometry(Ionization Techniques) by Ashutosh PankeAshutosh Panke
The document discusses various ionization techniques used in mass spectrometry. It describes several gas phase ionization methods including electron impact ionization, chemical ionization, and field ionization. It also discusses several desorption ionization techniques, notably fast atom bombardment, matrix assisted laser desorption/ionization, electrospray ionization, and surface enhanced laser desorption/ionization. The document provides details on the mechanisms and applications of these various ionization methods. It also categorizes mass analyzers and discusses time-of-flight mass analyzers.
Mass spectrometry involves ionizing molecule samples and then measuring their mass-to-charge ratios. The samples are bombarded with electrons to produce molecular ions, which then fragment into product ions. These ions are separated based on their mass-to-charge ratios and detected, producing a mass spectrum that shows the abundances of each ion. This spectrum provides structural information about the precursor molecule and can be used to identify unknown compounds. Mass spectrometry is widely applied across many scientific fields including pharmaceutical analysis, environmental testing, and forensics.
This document provides an overview of the key components and operating principles of mass spectrometry. It discusses the inlet system, ion sources, mass analyzers, detectors, and vacuum system. Common types of ion sources like electron impact and chemical ionization are described. Popular mass analyzers such as quadrupole, time-of-flight, ion trap, and double focusing are explained. The document also covers the theory behind how mass spectrometry separates ions based on their mass-to-charge ratio and discusses the need for high vacuum levels in mass spectrometers.
The document discusses UV-visible spectroscopy, which involves measuring the absorption of ultraviolet or visible radiation by molecules as they transition between energy levels. It explains the basic concepts of spectroscopy including electromagnetic radiation, absorption curves, electronic transitions, and Beer's and Lambert's laws which describe the relationship between absorbance and analyte concentration. The principles of UV-visible spectroscopy are useful for qualitative and quantitative analysis of compounds in various applications.
The document discusses mass spectrometry and provides information on various topics related to it including:
- Types of ions produced including molecular ions, fragment ions, and metastable ions.
- Common fragmentation patterns for different functional groups such as alkanes losing alkyl groups, alkenes forming allylic ions, and aromatics fragmenting at benzylic carbons.
- General rules for fragmentation including favored cleavage at branched points and loss of the largest substituent from a branch.
- Examples of mass spectra and prominent peaks are shown for compounds like ethanol, 2-pentanone, and hydrocinnamaldehyde to illustrate fragmentation patterns.
Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
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.
The document discusses UV-Vis spectroscopy, including an introduction to electronic transitions observed in UV-Vis spectroscopy, instrumentation used in UV-Vis spectroscopy, and components of UV-Vis spectrometers such as sources, sample containers, monochromators, and detectors. Selection rules that determine which electronic transitions are allowed are also covered.
Mass spectroscopy, Ionization techniques and types of mass analyzers Muhammad Asif Shaheeen
Mass spectroscopy is a technique used to determine the molecular mass and elemental composition of a compound. It works by ionizing molecules using electron bombardment or chemical ionization and then separating the resulting ions based on their mass-to-charge ratio using electric and magnetic fields. The instrument consists of an ion source, a mass analyzer, and an ion detector. Common ion sources include electron impact, chemical ionization, and electrospray ionization, with each having advantages for different types of samples. The document provides detailed explanations of the basic principles and components of mass spectroscopy.
Mass spectrometry is a technique that uses high energy electrons to break molecules into fragments. It then measures the masses of the fragments to reveal information about the molecular structure. Key aspects of mass spectrometry include the ionization source, mass analyzer, and detector. Common ionization methods are electron impact, electrospray, and MALDI, with softer methods like electrospray and MALDI used for larger molecules like proteins. Mass analyzers separate the ions by mass to charge ratio and include quadrupoles, time-of-flight, and magnetic sectors. The detector then counts the ions to produce a mass spectrum.
This document provides an overview of different ionization techniques used in mass spectrometry. It discusses gas phase ionization methods like electron impact and chemical impact ionization. It also covers desorptive ionization techniques such as field desorption, fast atom bombardment, and matrix-assisted laser desorption ionization. Finally, it summarizes evaporative ionization methods like atmospheric pressure chemical ionization and atmospheric pressure photoionization. The document aims to explain the basic principles, applications, advantages, and limitations of various ionization methods for mass spectrometry analysis.
This document discusses various ionization techniques used in mass spectrometry. It describes the electron ionization process where a sample is ionized by high energy electrons in an ion source. The document outlines different ionization methods including gas phase sources like electron ionization and chemical ionization, as well as desorption sources like field ionization. It provides details on the electron ionization process, chemical ionization using various reagent gases, and field ionization which uses a strong electric field to ionize samples. Advantages and disadvantages of each technique are also summarized.
Atomic emission spectroscopy is a technique that uses the intensity of light emitted from atoms excited by a heat source to determine the quantity of elements in a sample. The sample is converted to free atoms using a flame or electrothermal atomizer, then excited. A monochromator is used to selectively monitor the emission lines, and a detector measures the light intensity. This intensity is proportional to the number of atoms present. The technique can be used to identify and determine trace amounts of metals in samples like alloys and oils.
This presentation discusses various ionization techniques used in mass spectrometry. It begins with an introduction to the history and basic principles of mass spectrometry. It then describes several ionization methods including electron ionization, chemical ionization, desorption chemical ionization, field desorption, fast atom bombardment, and matrix-assisted laser desorption ionization. For each technique, it discusses the ionization process, sample introduction methods, advantages, limitations, and applicable mass ranges. The presentation provides an overview of the key ionization techniques used in mass spectrometry and their characteristics.
The document discusses two-dimensional nuclear magnetic resonance spectroscopy (2D NMR). 2D NMR provides more structural information about molecules than 1D NMR. There are several types of 2D NMR experiments that provide different information, including COSY, TOCSY, HSQC, and NOESY. These experiments establish correlations between nuclei that are directly bonded or spatially close. 2D NMR is useful for determining molecular structures, especially of complex biomolecules like proteins.
Mass spectrometry is a technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio. It can be used to determine molecular masses and elucidate molecular structures of organic compounds. There are several types of ions produced including molecular ions, fragment ions, and isotope ions. Compounds undergo various fragmentation modes like homolytic cleavage, heterolytic cleavage, retro-Diels-Alder reactions, hydrogen transfers and McLafferty rearrangements. Mass spectrometry has applications in fields like drug development, environmental analysis, and clinical diagnosis.
Mass spectrometry is a technique used to identify molecules based on their mass. It works by ionizing chemical compounds to generate molecular or fragment ions and measuring their mass-to-charge ratios. The document discusses the basic principles and components of a mass spectrometer, including ionization, separation of ions based on mass, and detection. It also covers common fragmentation patterns observed for different classes of compounds like hydrocarbons, alcohols, aromatics, and others. General rules for fragmentation are provided along with examples to illustrate how structural information can be determined.
this ppt contain all basic information related to the mass spectrometry like introduction, principle of MS, type of ions, fragmentation processes eg. mcLafferty rearrangement, alpha clevage, sigma bond clevage, retro-diels-alder reaction
13C-NMR spectroscopy provides information about organic compounds. It can determine the number of non-equivalent carbon atoms and identify carbon types like methyl, methylene, aromatic, and carbonyl groups. 13C signals are spread over a wider range than 1H NMR, making individual carbons easier to identify. Challenges include the low natural abundance of 13C and its lower gyromagnetic ratio. Techniques like signal averaging, Fourier transforms, and decoupling are used to overcome these issues and provide detailed 13C NMR spectra.
mass spectrometry, also called mass spectroscopy, analytic technique by which chemical substances are identified by the sorting of gaseous ions in electric and magnetic fields according to their mass-to-charge ratios.
Interfaces in chromatography [LC-MS, GC-MS, HPTLC, LC, GC]Shikha Popali
THE INTERFACES OF CHROMATOGRAPHY INCLUDES THE CHROMATOGRAPHY CRITEREA WHERE THE DIFFERENT CHROMATOGRAPHY ARE EXPLAINED IN DETAIL WITH PRACTICAL EXAMPLES AND THEIR IMAGES.
1) Mass spectroscopy involves ionizing compounds and characterizing the resulting ions based on their mass-to-charge ratio.
2) When a molecule is bombarded with electrons, it forms a molecular or parent ion by losing an electron.
3) The molecular ion peak corresponds to the intact molecule and gives the molecular weight of the compound.
Mass spectrometry is a technique used to determine the molecular mass and elemental composition of compounds. It works by ionizing molecules using electron bombardment, which causes the molecules to fragment into ions of various m/z ratios. The ions are then separated by mass analyzers based on their m/z and detected. This provides information about the molecular mass and structure of the compound being analyzed. Mass spectrometry can analyze solids, liquids, and gases.
Mass spectroscopy for MSc I Chemistry of SPPUsiraj174
* Using Rule of 13:
* Molecular mass = 128
* 128/13 = 9 with remainder of 8
* So the hydrocarbon formula is C9H9+8 = C9H17
* It is given that there are 8 hydrogens
* So remove 8 hydrogens from C9H17 to get C9H9
Therefore, the molecular formula is C9H9
Mass spectrometry is a technique that uses the deflection of charged particles by a magnetic field to determine the relative masses of molecular ions and fragments. It provides a great deal of information from small samples and can be used to determine molecular mass, structure, and purity. Various ionization sources like electron ionization, chemical ionization, fast atom bombardment, and matrix-assisted laser desorption/ionization are used to vaporize and ionize samples for analysis in mass analyzers such as quadrupoles, ion traps, and time-of-flight instruments. Mass spectra provide the abundance of ions as a function of their mass-to-charge ratio and can reveal molecular structure through characteristic fragmentation patterns.
Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
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.
The document discusses UV-Vis spectroscopy, including an introduction to electronic transitions observed in UV-Vis spectroscopy, instrumentation used in UV-Vis spectroscopy, and components of UV-Vis spectrometers such as sources, sample containers, monochromators, and detectors. Selection rules that determine which electronic transitions are allowed are also covered.
Mass spectroscopy, Ionization techniques and types of mass analyzers Muhammad Asif Shaheeen
Mass spectroscopy is a technique used to determine the molecular mass and elemental composition of a compound. It works by ionizing molecules using electron bombardment or chemical ionization and then separating the resulting ions based on their mass-to-charge ratio using electric and magnetic fields. The instrument consists of an ion source, a mass analyzer, and an ion detector. Common ion sources include electron impact, chemical ionization, and electrospray ionization, with each having advantages for different types of samples. The document provides detailed explanations of the basic principles and components of mass spectroscopy.
Mass spectrometry is a technique that uses high energy electrons to break molecules into fragments. It then measures the masses of the fragments to reveal information about the molecular structure. Key aspects of mass spectrometry include the ionization source, mass analyzer, and detector. Common ionization methods are electron impact, electrospray, and MALDI, with softer methods like electrospray and MALDI used for larger molecules like proteins. Mass analyzers separate the ions by mass to charge ratio and include quadrupoles, time-of-flight, and magnetic sectors. The detector then counts the ions to produce a mass spectrum.
This document provides an overview of different ionization techniques used in mass spectrometry. It discusses gas phase ionization methods like electron impact and chemical impact ionization. It also covers desorptive ionization techniques such as field desorption, fast atom bombardment, and matrix-assisted laser desorption ionization. Finally, it summarizes evaporative ionization methods like atmospheric pressure chemical ionization and atmospheric pressure photoionization. The document aims to explain the basic principles, applications, advantages, and limitations of various ionization methods for mass spectrometry analysis.
This document discusses various ionization techniques used in mass spectrometry. It describes the electron ionization process where a sample is ionized by high energy electrons in an ion source. The document outlines different ionization methods including gas phase sources like electron ionization and chemical ionization, as well as desorption sources like field ionization. It provides details on the electron ionization process, chemical ionization using various reagent gases, and field ionization which uses a strong electric field to ionize samples. Advantages and disadvantages of each technique are also summarized.
Atomic emission spectroscopy is a technique that uses the intensity of light emitted from atoms excited by a heat source to determine the quantity of elements in a sample. The sample is converted to free atoms using a flame or electrothermal atomizer, then excited. A monochromator is used to selectively monitor the emission lines, and a detector measures the light intensity. This intensity is proportional to the number of atoms present. The technique can be used to identify and determine trace amounts of metals in samples like alloys and oils.
This presentation discusses various ionization techniques used in mass spectrometry. It begins with an introduction to the history and basic principles of mass spectrometry. It then describes several ionization methods including electron ionization, chemical ionization, desorption chemical ionization, field desorption, fast atom bombardment, and matrix-assisted laser desorption ionization. For each technique, it discusses the ionization process, sample introduction methods, advantages, limitations, and applicable mass ranges. The presentation provides an overview of the key ionization techniques used in mass spectrometry and their characteristics.
The document discusses two-dimensional nuclear magnetic resonance spectroscopy (2D NMR). 2D NMR provides more structural information about molecules than 1D NMR. There are several types of 2D NMR experiments that provide different information, including COSY, TOCSY, HSQC, and NOESY. These experiments establish correlations between nuclei that are directly bonded or spatially close. 2D NMR is useful for determining molecular structures, especially of complex biomolecules like proteins.
Mass spectrometry is a technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio. It can be used to determine molecular masses and elucidate molecular structures of organic compounds. There are several types of ions produced including molecular ions, fragment ions, and isotope ions. Compounds undergo various fragmentation modes like homolytic cleavage, heterolytic cleavage, retro-Diels-Alder reactions, hydrogen transfers and McLafferty rearrangements. Mass spectrometry has applications in fields like drug development, environmental analysis, and clinical diagnosis.
Mass spectrometry is a technique used to identify molecules based on their mass. It works by ionizing chemical compounds to generate molecular or fragment ions and measuring their mass-to-charge ratios. The document discusses the basic principles and components of a mass spectrometer, including ionization, separation of ions based on mass, and detection. It also covers common fragmentation patterns observed for different classes of compounds like hydrocarbons, alcohols, aromatics, and others. General rules for fragmentation are provided along with examples to illustrate how structural information can be determined.
this ppt contain all basic information related to the mass spectrometry like introduction, principle of MS, type of ions, fragmentation processes eg. mcLafferty rearrangement, alpha clevage, sigma bond clevage, retro-diels-alder reaction
13C-NMR spectroscopy provides information about organic compounds. It can determine the number of non-equivalent carbon atoms and identify carbon types like methyl, methylene, aromatic, and carbonyl groups. 13C signals are spread over a wider range than 1H NMR, making individual carbons easier to identify. Challenges include the low natural abundance of 13C and its lower gyromagnetic ratio. Techniques like signal averaging, Fourier transforms, and decoupling are used to overcome these issues and provide detailed 13C NMR spectra.
mass spectrometry, also called mass spectroscopy, analytic technique by which chemical substances are identified by the sorting of gaseous ions in electric and magnetic fields according to their mass-to-charge ratios.
Interfaces in chromatography [LC-MS, GC-MS, HPTLC, LC, GC]Shikha Popali
THE INTERFACES OF CHROMATOGRAPHY INCLUDES THE CHROMATOGRAPHY CRITEREA WHERE THE DIFFERENT CHROMATOGRAPHY ARE EXPLAINED IN DETAIL WITH PRACTICAL EXAMPLES AND THEIR IMAGES.
1) Mass spectroscopy involves ionizing compounds and characterizing the resulting ions based on their mass-to-charge ratio.
2) When a molecule is bombarded with electrons, it forms a molecular or parent ion by losing an electron.
3) The molecular ion peak corresponds to the intact molecule and gives the molecular weight of the compound.
Mass spectrometry is a technique used to determine the molecular mass and elemental composition of compounds. It works by ionizing molecules using electron bombardment, which causes the molecules to fragment into ions of various m/z ratios. The ions are then separated by mass analyzers based on their m/z and detected. This provides information about the molecular mass and structure of the compound being analyzed. Mass spectrometry can analyze solids, liquids, and gases.
Mass spectroscopy for MSc I Chemistry of SPPUsiraj174
* Using Rule of 13:
* Molecular mass = 128
* 128/13 = 9 with remainder of 8
* So the hydrocarbon formula is C9H9+8 = C9H17
* It is given that there are 8 hydrogens
* So remove 8 hydrogens from C9H17 to get C9H9
Therefore, the molecular formula is C9H9
Mass spectrometry is a technique that uses the deflection of charged particles by a magnetic field to determine the relative masses of molecular ions and fragments. It provides a great deal of information from small samples and can be used to determine molecular mass, structure, and purity. Various ionization sources like electron ionization, chemical ionization, fast atom bombardment, and matrix-assisted laser desorption/ionization are used to vaporize and ionize samples for analysis in mass analyzers such as quadrupoles, ion traps, and time-of-flight instruments. Mass spectra provide the abundance of ions as a function of their mass-to-charge ratio and can reveal molecular structure through characteristic fragmentation patterns.
Mass spectroscopy for M Sc I Chemistry SPPUsiraj174
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of ions. It involves converting the sample into gaseous ions, separating the ions based on their mass-to-charge ratio, and detecting the relative abundance of each ion. There are four key stages: ionization, acceleration, deflection according to mass-to-charge ratio, and detection. Different types of peaks in a mass spectrum provide information about the molecule, including the molecular ion peak, which indicates the molecular mass, and fragment ion peaks, which result from fragmentation of the molecular ion. Rules like the nitrogen rule and rule of 13 can help determine molecular formulas from mass spectrometry data.
Mass spectrometry is an analytical technique that identifies unknown compounds and quantifies known materials by measuring their mass-to-charge ratios. It works by ionizing chemical compounds, generating charged molecule fragments, and measuring their mass-to-charge ratios using techniques like time-of-flight analysis. The document discusses the principles, instrumentation including ion sources, mass analyzers, and detectors, applications in fields like proteomics and metabolomics, and guidelines for interpreting mass spectra.
This document discusses mass spectrometry and provides information on several related topics:
- Mass spectrometry involves ionizing molecules and analyzing the resulting ions based on their mass-to-charge ratios to obtain molecular fingerprints.
- Different ionization methods like electron ionization, chemical ionization, electrospray ionization, and matrix-assisted laser desorption/ionization are described.
- Mass analyzers including quadrupoles and time-of-flight instruments are discussed. Factors like resolution, mass accuracy, calibration, adduct formation, and fragmentation are also covered.
i. The fragment I can identify is C3H7+ with m/z 57.
ii. The molecular ion is M+ with m/z 88, indicating the molecular formula is C6H14O. The functional groups are alcohol (-OH) and alkyl groups (-CH3, -CH2-).
iii. Expected fragmentation processes:
- Loss of H2O (18 Da) to form M+ - 18
- Loss of CH3 (15 Da) to form M+ - 15
- Loss of C2H5 (29 Da) to form M+ - 29
iv. The peaks at m/z 57, 71 and 73 correspond to the fragments C3H7+, M
This document provides an overview of mass spectrometry. It defines mass spectrometry as a technique for determining the molecular mass and composition of organic and inorganic compounds. The document outlines the basic components and working principle of a mass spectrometer. It discusses sample ionization, mass analysis, and ion detection. Fragmentation patterns are described along with examples of mass spectra for different compound classes like alkanes, alkenes, alkynes, aromatics, and alcohols. The history of mass spectrometry is also summarized.
Mass spectrometry (MS) is an analytical technique that is used to measure the molecular weight of the compounds. The results are typically presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio.
This document provides an overview of the application of mass spectrometry in pharmaceutical and biomedical analysis. It discusses the basic components and working of a mass spectrometer, including ionization, mass analysis, and detection. It also covers mass spectrometry techniques such as LC-MS, GC-MS, and MS-MS, and their uses in applications like structure elucidation, impurity profiling, metabolomics, and proteomics. The document concludes with a discussion of hyphenated techniques that combine chromatography with mass spectrometry for improved sensitivity, selectivity, and specificity.
It is an analytical technique useful for the determination of molecular mass, molecular formula and fragmentation pattern of particular molecule and compounds. It has greater application in pharmaceutical and medicinal fields.
Mass spectroscopy is a technique used to identify molecules based on their mass. It works by ionizing molecules and then separating the resulting ions based on their mass-to-charge ratio. The document discusses the basic principles and instrumentation of mass spectroscopy. It explains how molecules are ionized by bombarding them with electrons, then the ions are accelerated and deflected based on their mass-to-charge ratios before being detected. Key aspects like molecular ion peaks, fragmentation patterns, and isotopic peaks are described to help interpret mass spectra.
Mass Spectroscopy (Instrumentation & Spectral analysis ).pptxAquib Siddiqui
Mass spectrometry is an analytical technique that identifies chemicals in a sample by measuring the mass-to-charge ratio of gas-phase ions. Samples are converted to rapidly moving positive ions via electron bombardment, then separated based on their mass-to-charge ratios. A mass spectrum plots relative abundance against mass-to-charge ratio and is used to determine elemental composition, molecular masses, and elucidate chemical structures. During analysis, molecules are ionized, accelerated, deflected according to their mass, and detected, providing information about a sample's composition.
Mass spectrometry works by ionizing chemical substances and then using magnetic and electric fields to separate and measure the ions based on their mass-to-charge ratio. Samples are ionized through techniques like electron ionization or electrospray ionization. Ions are then accelerated and passed through a mass analyzer which separates them based on their m/z ratios. Finally, a detector measures the abundance of each ion and the results are presented as a mass spectrum. Mass spectrometry has many applications like pharmaceutical analysis, environmental analysis, and forensic or clinical uses.
This document provides an overview of mass spectrometry. It begins with an introduction to mass spectrometry, explaining that it is a technique used to analyze molecules by ionizing them and measuring the mass-to-charge ratios of the ions produced. It then covers the basic principles of mass spectrometry, describing how molecules are ionized by bombarding them with electrons and how the ions are separated and detected based on their mass-to-charge ratios. The remainder of the document discusses the theory behind mass spectrometry, describes common types of mass spectrometers, and outlines the ionization and fragmentation processes involved in mass spectrometry analysis.
Mass spectrometry allows determination of molecular mass, molecular formula, and some structural features. It works by vaporizing and ionizing a sample using electron bombardment, which knocks an electron off each molecule to produce a molecular ion. The mass spectrometer then separates the ions based on their mass-to-charge ratio, which allows identification of the molecular ion peak corresponding to the molecular weight. Isotope peaks from elements like carbon can provide structural information. Fragmentation patterns are also used for structural analysis.
Various Computational Tools used in Drug DesignFirujAhmed2
Drug discovery is the process of identifying and developing new medications or drugs to treat diseases and improve human health. It involves a multidisciplinary approach that combines scientific research, experimentation, and testing to discover and create effective and safe pharmaceutical compounds.
Drug design, is the inventive process of finding new medications based on the knowledge of a biological target. The drug is most commonly an organic small molecule that activates or inhibits the function of a biomolecule such as a protein, which in turn results in a therapeutic benefit to the patient.
Process Chemistry Fire Hazards Presentation.pptx for M. Pharm pharmaceutica...FirujAhmed2
This document discusses fire hazards and types of fires. It explains that a fire needs three elements - heat, fuel, and oxygen - which is known as the fire triangle. There are several types of fire hazards, including electrical, process, storage, smoking, and friction hazards. Fires are classified into five classes - Class A involves ordinary combustibles, Class B involves flammable liquids and gases, Class C involves energized electrical equipment, Class D involves combustible metals, and Class K involves cooking fires.
An artificial enzyme is a synthetic organic molecule or ion that mimics one or more functions of an enzyme.
Molecules are designed and modified to achieve some desirable features of enzymes.
Protein engineering has been developed to design and synthesize molecules with the attributes of enzymes for non-natural reactions.
They have a molecular weight of less than 2000 Dalton.
They have the ability to stabilize at a higher temperature.
They are also known as synzymes or enzyme mimics.
This document discusses mechanisms of anticancer drug resistance and approaches to overcome resistance. It covers several key points:
1. Cancer cells can develop resistance to chemotherapy drugs through various mechanisms like drug inactivation, target alteration, drug efflux, DNA damage repair, heterogeneity, and inhibiting cell death.
2. Nanomedicine is a promising therapeutic approach to overcome resistance by improving drug distribution, efficacy and reducing side effects. Nanoparticles can be activated by light to heat and kill cancer cells.
3. Various types of nanoparticles are being studied for cancer treatment including lipid-based, polymer-based, dendrimers, carbon-based, and metallic/magnetic nanoparticles. Understanding resistance mechanisms and safety/efficacy
Face to face non verbal communication skills FirujAhmed2
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
synthetic Reagents and its application DiazomethaneFirujAhmed2
Diazomethane is a yellow, poisonous, potentially explosive compound with the chemical formula CH2N2. It is a valuable synthetic reagent that is used for methylation reactions and in the synthesis of heterocyclic compounds. Diazomethane can be prepared through Pechmann's method involving the reaction of methylamine with ethyl chlorofomate or through hydrolysis of an ethereal solution of an N-methyl nitrosamide with aqueous base. It is chemically very reactive and transforms functional groups, making it useful for a variety of synthetic applications.
The document describes the Ugi reaction, a multi-component reaction where a ketone or aldehyde, amine, isocyanide, and carboxylic acid come together to form a bis-amide. It was first reported in 1959 by Ivar Karl Ugi. The reaction has high atom economy and yields, occurs rapidly at room temperature, and is uncatalyzed. It has applications in synthesizing chemical libraries and multiple compounds in one step, such as the HIV drug Crixivan. The mechanism involves imine formation, proton exchange, additions of the isocyanide and carboxylic acid, and a Mumm's rearrangement.
Giloy in Ayurveda - Classical Categorization and SynonymsPlanet Ayurveda
Giloy, also known as Guduchi or Amrita in classical Ayurvedic texts, is a revered herb renowned for its myriad health benefits. It is categorized as a Rasayana, meaning it has rejuvenating properties that enhance vitality and longevity. Giloy is celebrated for its ability to boost the immune system, detoxify the body, and promote overall wellness. Its anti-inflammatory, antipyretic, and antioxidant properties make it a staple in managing conditions like fever, diabetes, and stress. The versatility and efficacy of Giloy in supporting health naturally highlight its importance in Ayurveda. At Planet Ayurveda, we provide a comprehensive range of health services and 100% herbal supplements that harness the power of natural ingredients like Giloy. Our products are globally available and affordable, ensuring that everyone can benefit from the ancient wisdom of Ayurveda. If you or your loved ones are dealing with health issues, contact Planet Ayurveda at 01725214040 to book an online video consultation with our professional doctors. Let us help you achieve optimal health and wellness naturally.
Debunking Nutrition Myths: Separating Fact from Fiction"AlexandraDiaz101
In a world overflowing with diet trends and conflicting nutrition advice, it’s easy to get lost in misinformation. This article cuts through the noise to debunk common nutrition myths that may be sabotaging your health goals. From the truth about carbohydrates and fats to the real effects of sugar and artificial sweeteners, we break down what science actually says. Equip yourself with knowledge to make informed decisions about your diet, and learn how to navigate the complexities of modern nutrition with confidence. Say goodbye to food confusion and hello to a healthier you!
Discover the benefits of homeopathic medicine for irregular periods with our guide on 5 common remedies. Learn how these natural treatments can help regulate menstrual cycles and improve overall menstrual health.
Visit Us: https://drdeepikashomeopathy.com/service/irregular-periods-treatment/
5-hydroxytryptamine or 5-HT or Serotonin is a neurotransmitter that serves a range of roles in the human body. It is sometimes referred to as the happy chemical since it promotes overall well-being and happiness.
It is mostly found in the brain, intestines, and blood platelets.
5-HT is utilised to transport messages between nerve cells, is known to be involved in smooth muscle contraction, and adds to overall well-being and pleasure, among other benefits. 5-HT regulates the body's sleep-wake cycles and internal clock by acting as a precursor to melatonin.
It is hypothesised to regulate hunger, emotions, motor, cognitive, and autonomic processes.
STUDIES IN SUPPORT OF SPECIAL POPULATIONS: GERIATRICS E7shruti jagirdar
Unit 4: MRA 103T Regulatory affairs
This guideline is directed principally toward new Molecular Entities that are
likely to have significant use in the elderly, either because the disease intended
to be treated is characteristically a disease of aging ( e.g., Alzheimer's disease) or
because the population to be treated is known to include substantial numbers of
geriatric patients (e.g., hypertension).
Summer is a time for fun in the sun, but the heat and humidity can also wreak havoc on your skin. From itchy rashes to unwanted pigmentation, several skin conditions become more prevalent during these warmer months.
Nano-gold for Cancer Therapy chemistry investigatory projectSIVAVINAYAKPK
chemistry investigatory project
The development of nanogold-based cancer therapy could revolutionize oncology by providing a more targeted, less invasive treatment option. This project contributes to the growing body of research aimed at harnessing nanotechnology for medical applications, paving the way for future clinical trials and potential commercial applications.
Cancer remains one of the leading causes of death worldwide, prompting the need for innovative treatment methods. Nanotechnology offers promising new approaches, including the use of gold nanoparticles (nanogold) for targeted cancer therapy. Nanogold particles possess unique physical and chemical properties that make them suitable for drug delivery, imaging, and photothermal therapy.
Breast cancer: Post menopausal endocrine therapyDr. Sumit KUMAR
Breast cancer in postmenopausal women with hormone receptor-positive (HR+) status is a common and complex condition that necessitates a multifaceted approach to management. HR+ breast cancer means that the cancer cells grow in response to hormones such as estrogen and progesterone. This subtype is prevalent among postmenopausal women and typically exhibits a more indolent course compared to other forms of breast cancer, which allows for a variety of treatment options.
Diagnosis and Staging
The diagnosis of HR+ breast cancer begins with clinical evaluation, imaging, and biopsy. Imaging modalities such as mammography, ultrasound, and MRI help in assessing the extent of the disease. Histopathological examination and immunohistochemical staining of the biopsy sample confirm the diagnosis and hormone receptor status by identifying the presence of estrogen receptors (ER) and progesterone receptors (PR) on the tumor cells.
Staging involves determining the size of the tumor (T), the involvement of regional lymph nodes (N), and the presence of distant metastasis (M). The American Joint Committee on Cancer (AJCC) staging system is commonly used. Accurate staging is critical as it guides treatment decisions.
Treatment Options
Endocrine Therapy
Endocrine therapy is the cornerstone of treatment for HR+ breast cancer in postmenopausal women. The primary goal is to reduce the levels of estrogen or block its effects on cancer cells. Commonly used agents include:
Selective Estrogen Receptor Modulators (SERMs): Tamoxifen is a SERM that binds to estrogen receptors, blocking estrogen from stimulating breast cancer cells. It is effective but may have side effects such as increased risk of endometrial cancer and thromboembolic events.
Aromatase Inhibitors (AIs): These drugs, including anastrozole, letrozole, and exemestane, lower estrogen levels by inhibiting the aromatase enzyme, which converts androgens to estrogen in peripheral tissues. AIs are generally preferred in postmenopausal women due to their efficacy and safety profile compared to tamoxifen.
Selective Estrogen Receptor Downregulators (SERDs): Fulvestrant is a SERD that degrades estrogen receptors and is used in cases where resistance to other endocrine therapies develops.
Combination Therapies
Combining endocrine therapy with other treatments enhances efficacy. Examples include:
Endocrine Therapy with CDK4/6 Inhibitors: Palbociclib, ribociclib, and abemaciclib are CDK4/6 inhibitors that, when combined with endocrine therapy, significantly improve progression-free survival in advanced HR+ breast cancer.
Endocrine Therapy with mTOR Inhibitors: Everolimus, an mTOR inhibitor, can be added to endocrine therapy for patients who have developed resistance to aromatase inhibitors.
Chemotherapy
Chemotherapy is generally reserved for patients with high-risk features, such as large tumor size, high-grade histology, or extensive lymph node involvement. Regimens often include anthracyclines and taxanes.
“Psychiatry and the Humanities”: An Innovative Course at the University of Mo...Université de Montréal
“Psychiatry and the Humanities”: An Innovative Course at the University of Montreal Expanding the medical model to embrace the humanities. Link: https://www.psychiatrictimes.com/view/-psychiatry-and-the-humanities-an-innovative-course-at-the-university-of-montreal
Ageing, the Elderly, Gerontology and Public Health
MASS SPECTROSCOPY.ppt
1. Mass Spectroscopy
Mass Spectrometry is an analytical spectroscopic
tool primarily concerned with the separation of
molecular (and atomic) species according to their
mass.
What information can be determined?
• Molecular weight
• Molecular formula
• Structure (from fragmentation fingerprint)
• Isotopic incorporation / distribution
• Protein sequence
2. 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 and peptides
Oligonucleotides
Environmental analysis
Pesticides on foods
Soil and groundwater contamination
Forensic analysis/clinical
Applications of Mass Spectrometry
3. Atom or molecule is hit by high-energy electron
Principles of Electron-Impact Mass Spectrometry
e–
4. Atom or molecule is hit by high-energy electron
electron is deflected but transfers much of its
energy to the molecule
e–
6. This energy-rich species ejects an electron.
forming a positively charged, odd-electron species
called the molecular ion
e–
+
•
7. Atom or molecule is hit by high-energy electron
from an electron beam at 10ev
e–
beam
forming a positively charged, odd-electron
species called the molecular ion
e–
+
•
8. Molecular ion passes between poles of a
magnet and is deflected by magnetic field
amount of
deflection depends
on mass-to-charge
ratio
highest m/z
deflected least
lowest m/z
deflected most
+
•
9. If the only ion that is present is the
molecular ion, mass spectrometry provides a
way to measure the molecular weight of a
compound and is often used for this purpose.
However, the molecular ion often
fragments to a mixture of species of lower
m/z.
11. The molecular ion dissociates to a cation
and a radical.
+ •
Usually several fragmentation pathways are
available and a mixture of ions is produced.
12. mixture of ions of
different mass
gives separate peak
for each m/z
intensity of peak
proportional to
percentage of each
ion of different
mass in mixture
separation of peaks
depends on relative
mass
+
+
+
+
+
+
13. mixture of ions of
different mass
gives separate peak
for each m/z
intensity of peak
proportional to
percentage of each
atom of different
mass in mixture
separation of peaks
depends on relative
mass
+ + + +
+ +
14. What’s in a Mass Spectrum?
Mass, as m/z. Z is the charge, and for doubly charged ions (often seen in
macromolecules), masses show up at half their proper value
High
mass
[M+H]+(CI)
Or M•+ (EI)
“molecular ion”
Unit mass
spacing
Fragment Ions Derived from
molecular ion
or higher
weight
fragments
In CI, adduct ions,
[M+reagent gas]+
15. • Mass spectrum: A plot of the relative abundance
of ions versus their mass-to-charge ratio (m/z).
• Base peak: The most abundant peak.
– Assigned an arbitrary intensity of 100.
• The relative abundance of all other ions is reported
as a % of abundance of the base peak.
Mass Spectrum
16. • Molecular ion (M): A radical cation formed by removal
of a single electron from a parent molecule in a mass
spectrometer = MW.
• For our purposes, it does not matter which electron is
lost; radical cation character is delocalized throughout
the molecule; therefore, we write the molecular formula
of the parent molecule in brackets with:
– A plus sign to show that it is a cation.
– A dot to show that it has an odd number of electrons.
Molecular Ion
17. M + e- M+ + 2e-
Molecule High Energy
Electron
Molecular
Ion
(Radical Cation)
100
90
80
70
60
50
40
30
20
10
0
Intensity
(%
of
Base
Peak)
20 30 40 50 60 70 80 90
m / z
1-Pentanol - MW 88
CH3(CH2)3 – CH2OH
CH2OH+
M - (H2O and CH2=CH2)
M - (H2O and CH3)
M - H2O
M+ - 1
Molecular Ion Peak
Base Peak
M + e- M+ + 2e-
Molecule High Energy
Electron
Molecular
Ion
(Radical Cation)
M + e- M+ + 2e-
Molecule High Energy
Electron
Molecular
Ion
(Radical Cation)
100
90
80
70
60
50
40
30
20
10
0
Intensity
(%
of
Base
Peak)
20 30 40 50 60 70 80 90
m / z
1-Pentanol - MW 88
CH3(CH2)3 – CH2OH
CH2OH+
M - (H2O and CH2=CH2)
M - (H2O and CH3)
M - H2O
M+ - 1
Molecular Ion Peak
Base Peak
Mass Spectrum
18. – A partial MS of dopamine showing all peaks
with intensity equal to or greater than 0.5%
of base peak.
MS of dopamine
19. AN INSTRUMENT THAT GENERATES IONS FROM MOLECULES
AND MEASURES THEIR MASSES
THE ESSENTIAL COMPONENTS OF A MASS SPECTROMETER:
SAMPLE
INLET
ION
SOURCE
ION
ACCELERATOR
ION
ANALYSER
ION
DETECTOR
signal
COMPUTER
MASS SPECTRUM
DATABASE
0
50
100
0 10 20 30 40 50 60 70 80
2
15
27
41
53
69
84
1-Butene, 3,3-dimethyl-
MASS SPECTROMETER
20. Illustration of the basic components of a mass spectrometry system.
Ionization
Source
Mass
Analzyer
Detector
Inlet all ions
selected
ions
Data
System
Diagram of a simple mass spectrometer
22. 2. Atomic & Mass Number
A
Z X
atomic number
(number of protons)
(number of electrons)
mass number
(number of protons plus neutrons)
23. WAYS TO PRODUCE IONS
• Electron impact (EI) - vapor of sample is bombarded with
electrons: M + e 2e + M.+ fragments
• Chemical ionization (CI) - sample M collides with reagent
ions present in excess e.g.
CH4 + e CH4
.+ CH5
+
M + CH5
+ CH4 + MH+
• Fast Atom/Ion Bombardment (FAB)
• Laser Desorption & Matrix-Assisted Laser Desorption
(MALDI)
- hit the sample with a laser beam
• Electrospray Ionization (ESI) - a stream of solution passes
through a strong electric field (106 V/m)
24. 1. Electron Ionization (EI)
most common ionization technique, limited to
relatively low MW compounds (<600 amu)
2. Chemical Ionization (CI)
ionization with very little fragmentation, still for
low MW compounds (<800 amu)
3. Desorption Ionization (DI)
for higher MW or very labile compounds
4. Spray ionization (SI)
for LC-MS, biomolecules, etc.
Ionization Methods
25. • vaporized sample is bombarded with high
energy electrons (typically 70 eV)
• “hard” ionization method leads to significant
fragmentation
• ionization is efficient but non-selective
Electron Ionization (EI)
26. Electron Ionization
Advantages
• inexpensive, versatile and reproducible
• fragmentation gives structural information
• large databases if EI spectra exist and are
searchable
Disadvantages
• fragmentation at expense of molecular ion
• sample must be relatively volatile
27. Chemical Ionization (CI)
Vaporized sample reacts with pre-ionized reagent
gas via proton transfer, charge exchange,
electron capture, adduct formation, etc.
– Common CI reagents:
methane, ammonia, isobutane, hydrogen, methanol
• “soft” ionization gives little fragmentation
• selective ionization-only exothermic or
thermoneutral ion-molecule reactions will occur
• choice of reagent allows tuning of ionization
28. CI MS Sources
High Energy electrons
Sample Molecule MH
CH4
CH4 CH4
+ CH3
+ CH2
+
2
5
2
4
3
3
5
4
4
H
H
C
CH
CH
CH
CH
CH
CH
6
2
5
2
4
2
2
5
2
4
2
5
H
C
M
MH
H
C
H
C
MH
MH
H
C
CH
MH
MH
CH
Molecule Ions
29. Lets talk about mass!
• Atomic mass of Carbon
– 12.000000000000000000000000000 amu
• Atomic mass of Chlorine
– 35.4527 amu
• Atomic mass of Hydrogen
– 1.00794 amu
1amu = 1 dalton (Da)
30. • Resolution: A measure of how well a mass
spectrometer separates ions of different
mass.
– low resolution: Refers to instruments
capable of separating only ions that differ in
nominal mass; that is ions that differ by at
least 1 or more atomic mass units.
– high resolution: Refers to instruments
capable of separating ions that differ in
mass by as little as 0.0001 atomic mass unit.
Resolution
31. In
ten
sity
(%)
0
20
40
60
80
100
Mass [amu]
111.95 112.00 112.05 112.10
In
ten
sity
(%)
0
20
40
60
80
100
Mass [amu]
111.95 112.00 112.05 112.10
In
ten
sity
(%)
0
20
40
60
80
100
Mass [amu]
111.95 112.00 112.05 112.10
RP= 3,000 RP= 5,000 RP= 7,000
All resolving powers are FWHM
C6H5OF
C6H5Cl
Resolving Power Example
32. • High resolution data reports include ppm estimate
– ppm = parts per million (1 ppm = 0.0001%)
• 5 ppm @ m/z 300 = 300 * (5/106) = ±0.0015
Da
• 5 ppm @ m/z 3,000 = 3,000 * (5/106) =
±0.015 Da
• A molecule with mass of 44 could be C3H8, C2H4O,
CO2, or CN2H4.
• If a more exact mass is 44.029, pick the correct
structure from the table:
C3H8 C2H4O CO2 CN2H4
44.06260 44.02620 43.98983 44.03740
High Resolution MS
33. – C3H6O and C3H8O have nominal masses of 58 and
60, and can be distinguished by low-resolution MS.
– C3H8O and C2H4O2 both have nominal masses of 60.
– Distinguish between them by high-resolution MS.
C2 H4 O2
C3 H8 O
60.02112
60.05754
60
60
Molecular
Formula
Nominal
Mass
Precise
Mass
Resolution
– High resolution MS can replace elemental
analysis for chemical formula confirmation
34. • Atomic number is the
number of protons (+) in
the nucleus and
determines the element
identity.
• Isotopes of an element
have a different number
of neutrons in the
nucleus. Electrons (-)
form a cloud and most of
the volume of the atom.
• Electrons weigh very
little. Atomic weight is
basically the sum of the
number of protons and
neutrons.
What about isotopes?
Atomic Theory
35. • Atomic mass of Carbon
– 12.000 amu for 12C but 13.3355 for 13C
• Atomic mass of Chlorine
– 34.9688 amu for 35Cl and 36.9659 for 37Cl
• Atomic mass of Hydrogen
– 1.00794 amu for H and 2.0141 for D!
Get it now?
Most elements have more than one stable isotope.
– For example, most carbon atoms have a mass of 12 Da, but in nature,
1.1% of C atoms have an extra neutron, making their mass 13 Da.
38. • The most common elements giving rise to significant M + 2
peaks are chlorine and bromine.
– Chlorine in nature is 75.77% 35Cl and 24.23% 37Cl.
– A ratio of M to M + 2 of approximately 3:1 indicates the
presence of a single chlorine in a compound.
M+2 and M+1 Peaks
39. – Bromine in nature is 50.7% 79Br and 49.3% 81Br.
– A ratio of M to M + 2 of approximately 1:1 indicates
the presence of a single bromine in a compound.
M+2 and M+1 Peaks
40. • Sulfur is the only other element common to organic
compounds that gives a significant M + 2 peak.
– 32S = 95.02% and 34S = 4.21%
– Also 33S = 0.8%, an M+1 peak.
• Because M + 1 peaks are relatively low in intensity
compared to the molecular ion and often difficult to
measure with any precision, they are generally not
useful for accurate determinations of molecular
weight.
M+2 and M+1 Peaks
41. Nobel Prizes in Mass Spectrometry
1906- J.J. Thomson- m/z of electron
1911- W. Wien- anode rays have positive charge
1922- F. Aston- isotopes (first MS with velocity focusing)
1989- H. Dehmelt, W. Paul- quadrupole ion trap
1992- R.A. Marcus- RRKM theory of unimolecular dissociation
1996- Curl, Kroto, and Smalley- fullerenes (used MS)
2002- J. Fenn- electrospray ionization of biomolecules
K. Tanaka- laser desorption ionization of biomolecules
42. • Better carbocation wins and predominates “Stevenson’s Rule”
[M·]+ A+ + B· (neutral)
or
B+ + A·
EI
Fragmentation
Stevenson’s Rule:
– For simple bond cleavage, the fragment with lowest
ionization potential takes the charge
(in other words, the most stable ion is formed)
43. • The Game is, to rationalize these in terms of the structure
• Identify as many as possible, in terms of the parent
structure
• Generally, simply derived from the molecular ion
• Or, in a simple fashion from a significant higher mw
fragment.
• Simply, here means, ions don’t fly apart, split out neutrals
and then recombine.
• Fragments will make chemical sense
• A good approach is the “rule of 13” to write down a
molecular formula for an ion of interest.
• Especially in EI, we only identify major fragments
Fragment Ions
44. The “Even Electron Rule” dictates that even (non-radical)
ions will not fragment to give two radicals (pos• + neutral•)
(CI)
CI
[M+H]+ PH+ + N (neutral)
– Loss of neutral molecules, small stable, from MH+
– Loss of neutrals from protonated fragments
– Subsequent reprotonation after a loss
– Typically there is no ring cleavage (needs radical) or two
bond scissions.
– Depends highly on ion chemistry specifically acid-base
(proton affinities)
45. • Governed by product ion stability
• consideration
– octet rule
– resonance delocalization
– polarizability and hyperconjugation
– electronegativity
Fragmentation
46. General Fragmentation Pathways
– One-bond cleavages
a-cleavages
C OH
R
- R C OH C O
Cleave a to Heteroatoms like O, N
O
R
: .
+
•
R
O:
: .
neutral
+
+
Heterolytic cleavage
Observed in Mass Spec provided
that a good stabilized carbocation
can form
47. O O
O
: .
+
+
+
:
+
: :
Obs. in mass spec.
Acylium ions are
resonance-stabilized
neutral
Prominent for
ketones
CH3C=O+
m/z=43
Cleavage a to C=O groups
48. O
O O
M+• -45, loss of
ethoxy radical
O
+
C
+
O
O
+
Example
Ethyl 3-oxo-3-phenylpropanoate (Mol. Wt.: 192.21)
50. b-cleavages
– Cleave b to a heteroatom (capable of supporting positive charge)
RO
RO
RO
:
:
Obs. in Mass Spec
Resonance stabilized
neutral
+
+
+
Note the use of “half arrow” for one-electron movements. e.g homolytic cleavage
examples
Primary alcohols, m/z =31 CH2=OH+
Primary amines, m/z =30 CH2=NH2
+
m/z 30
+
+
•
b-cleavage
CH3 CH3
CH3 - CH- CH2 -CH2 -NH2 CH3 - CH- CH2 CH2 = NH2
51. Two-bond cleavages
– Eliminate H-X
– Retro Diels-Alder
–McLafferty rearrangement
+
C
C
O
C
C
H2
CH2
CR2
H
Y
-R2=CH2
Y = H, R, OH, OR
NR2
O
C
CH2
H
Y
O
C
CH2
H
Y
O
C
CH2
H
Y
need g-hydrogens
52. Alkane Fragmentation
• Long chains give homologous series of m/z = 14 units
• Long chains rarely lose methyl radical
• Straight chain alkanes give primary carbocation
• Branched alkanes have small or absent M+
• Enhanced fragmentation at branch points
C
H3 CH3
CH3
C
H3
C
H3
C
+
CH3
CH3.
Obs. in Mass Spec
+
neutral
+