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    w. paul developed ion trap techniue in 1953.
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  • W. Paul developed (not discovered) the ion trap technique in the 1950's - he got his Noble prize in 1989.
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  • MASS SPECTROMETRYMass spectrometry is a powerful analytical technique that is used to identify unknown compounds, to quantify known compounds, and to elucidate the structure and chemical properties of molecules. It is the smallest scale in the world, not because of the mass spectrometer’s size but because of the size what it weighs...molecules. According to the IUPAC (International Union of Pure and Applied Chemistry), it is the branch of science dealing with all aspects of mass spectroscopes and results obtained with these instruments. The information given by mass spectrometry is sometimes sufficient, frequently necessary, and always useful for identification of species.
  • Mass Spectrometry was started by J.J. Thomson. Until 1897, scientists believed atoms were indivisible; the ultimate particles of matter, but Thomson proved them wrong when he discovered that atoms contained particles known as electrons. He concluded this by his experiments on cathode rays. He found that the rays could be deflected by an electric field (in addition to magnetic fields, which was already known). By comparing the deflection of a beam of cathode rays by electric and magnetic fields he was able to measure the particle's mass. This showed that cathode rays were matter, but he found that the particles were about 2000 times lighter than the mass of the lightest atom, hydrogen. He concluded that the rays were composed of very light negatively charged particles which he called electron. He also concluded that neon is composed of two isotopes and them which was the first example of mass spectrometry. On his discovery he was awarded Nobel Prize in 1906.In 1919, Thomson, with the help of his student Francis Aston (who would go on to win his own Nobel Prize in Chemistry in 1922), built what later would be recognized as the first mass spectrometer to measure the masses of charged atoms. In their first mass spectrometer they measure the charge to mass ratio (z/m) for several ionic species. In the expression z/m, z is the charge number, i.e. the total charge on an ion divided by the elementary charge (e), and m is the nucleon number, i.e. the sum of the total number of protons and neutrons in an atom, molecule or ion. In modern mass spectrometry, the parameter measured is m/z, rather than z/m: the unit of m/z was recently designated the Thomson (Th).This instrument used gas discharge tubes to generate ions, which were then passed through parallel electric and magnetic fields. The ions were deflected into parabolic trajectories and then detected on a photographic plate.In 1934, First double focusing magnetic analyzer was invented by Johnson E.G., Nier A.O. In 1966, Munson and Field described chemical ionization (CI). One of the first soft ionization techniques
  • In 1968, Electrospray Ionization was invented by Dole M., Mack L.L., Hines R.L., Mobley R.C., Ferguson L.D., Alice M.B. In 1975, Atmospheric Pressure Chemical Ionization (APCI) was developed by Carroll D.I., Dzidic I., Stillwell R.N., Haegele K.D., Horning E.C.In 1985, Franz Hillenkamp, Michael Karas and co-workers describe and coin the term matrix-assisted laser desorption ionization (MALDI).In 1989, Wolfgang Paul receives the Nobel Prize in Physics "for the development of the ion trap technique"
  • An instrument which measures the ratio of mass to the number of charges of ions produced from elements and compounds. It is also of value in performing fundamental studies of the properties of gaseous ions.
  • Basic components of mass spectrometerFour basic components are, for the most part, standard in all mass spectrometers: a sample inlet, an ionization source, a mass analyzer and an ion detector. Some instruments combine the sample inlet and the ionization source, while others combine the mass analyzer and the detector. However, all sample molecules undergo the same processes. Sample molecules are introduced into the instrument through a sample inlet. Once inside the instrument, the sample molecules are converted to ions in the ionization source, before being electrostatically propelled into the mass analyzer. Ions are then separated according to their m/z within the mass analyzer. The detector converts the ion energy into electrical signals, which are then transmitted to a computer.

Transcript

  • 1. Mass Spectrometry
    Mussarat Jabeen
  • 2. Mass Spectrometry
    • Powerful analytical technique
    • 3. Smallest scale
    • 4. Destructive technique
    • 5. Useful for identification of species
    According to the IUPAC (International Union of Pure and Applied Chemistry), it is the branch of science dealing with all aspects of mass spectroscopes and results obtained with these instruments.
  • 6. Mass Spectrometry
    Contents
    Brief History of Mass Spectrometry
    Nobel prize pioneers
    Mass spectrometer
    Structural analysis and Fragmentation Patterns
    interpretation of mass spectrum
    Applications of mass spectrometry
  • 7. 1897
    1919
    1934
    1966
    Mass Spectrometry
    Brief History of Mass Spectrometry
    J.J. Thomson. Discovered electrons by cathode rays experiment. Nobel prize in 1906.
    Francis Aston recognized 1st mass spectrometer and measure z/m of ionic compounds.
    First double focusing magnetic analyzer was invented by Johnson and Neil.
    Munson and Field described chemical ionization.
  • 8. 1968
    1975
    1985
    1989
    Mass Spectrometry
    Electrospray Ionization was invented by Dole, Mack and friends.
    Atmospheric Pressure Chemical Ionization (APCI) was developed by Carroll and others.
    F. Hillenkamp, M.Karas and co-workers describe and coin the term matrix assisted laser desorption ionization (MALDI).
    w. Paul discovered the ion trap technique.
  • 9. Mass Spectrometry
    Nobel prize pioneers
  • 10. Mass Spectrometry
    Mass spectrometer
  • 11. Mass Spectrometry
    Understanding Mass Spectrometry
    In a mass spectrometer, the same thing is happening, except it's atoms and molecules that are being deflected, and it's electric or magnetic fields causing the deflection. It's also happening in a cabinet that can be as small as a microwave or as large as a chest freezer.
  • 12. Mass Spectrometry
    Mass spectrometer is similar to a prism.
    In the prism, light is separated into its component wavelengths which are then detected with an optical receptor, such as visualization. Similarly, in a mass spectrometer the generated ions are separated in the mass analyzer, digitized and detected by an ion detector.
  • 13. Mass Spectrometry
    Basic Components of Mass Spectrometer
    Four basic components
  • Mass spectrometer
    Sample Introduction Techniques
    Initial pressure of sample is 760 mmHg or ~10-6 torr
    Two techniques
    • Direct Insertion (commonly used in MALDI)
    • 17. Direct infusion or injection (commonly used in ESI)
  • Mass spectrometer
    Direct Insertion sample introduction technique
    very simple technique
    Sample is placed on a prob and inserted into ionization source and then subjected to any number of desorption processes, such as laser desorption or direct heating, to facilitate vaporization and ionization.
  • 18. Mass Spectrometry
    Direct infusion or injection sample introduction technique
    Frequently used due to high efficiently
    Used in coupling techniques like GC-MS and HPLC-MS
  • 19. Mass Spectrometry
    Ionization Methods used in Mass spectrometry
    Commonly used
    • Protonation
    • 20. Deprotonation
    • 21. Cationization
    • 22. Transfer of a charged molecule to the gas phase
    • 23. Electron ejection
    • 24. Electron capture
  • Mass Spectrometry
    Protonation
    Formation of positive ions by the addition of a proton
    Used for basic compounds like amines, peptides
    Used in MALDI, APCI and ESI
  • 25. Mass Spectrometry
    Deprotonation
    Give net negative charge of 1- by removal of one proton
    Used for acidic species like phenols, carboxylic acid, sulfonic acid etc.
    Used in MALDI, APCI and ESI
  • 26. Mass Spectrometry
    Cationization
    produces a charged complex by non-covalently adding a positively charged ion like alkali metal ion or ammonium ion to a neutral molecule.
    Used for Carbohydrates
    Used in MALDI, APCI and ESI
  • 27. Mass Spectrometry
    Transfer of a charged molecule to the gas phase
    Cation from solution to gas
    Used in MALDI or ESI
  • 28. Mass Spectrometry
    Electron ejection
    Electron is ejected to give positive ion
    Usually for non-polar compounds with low molecular weights like anthracene.
  • 29. Mass Spectrometry
    Electron capture
    a net negative charge of 1- is achieved with the absorption or capture of an electron.
    Used for halogenated compounds
  • 30. Mass Spectrometry
    Ionization Sources in mass spectrometer
    • Electrospray Ionization (ESI)
    • 31. Nanoelectrospray Ionization (NanoESI)
    • 32. Atmospheric Pressure Chemical Ionization (APCI)
    • 33. Atmospheric pressure photoionization (APPI)
    • 34. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)
    • 35. Fast Atom Bombardment (FAB)
    • 36. Electron Ionization (EI)
    • 37. Chemical Ionization (CI)
    • 38. Thermal ionization (TI)
  • Mass Spectrometry
    Types of
    Ionization Sources
    Hard ionization sources
    Soft ionization sources
    Little excess energy in molecule and produced unstable fragments which are again fragmented.
    leave excess energy in molecule and produced stable fragments which is not further fragarmented
  • 39. Mass Spectrometry
    Electrospray Ionization (ESI)
    The sample solution is sprayed from a region of the strong electric field at the tip of a metal nozzle maintained at a potential of anywhere from 700 V to 5000 V. The nozzle (or needle) to which the potential is applied serves to disperse the solution into a fine spray of charged droplets. Either dry gas, heat, or both are applied to the droplets at atmospheric pressure thus causing the solvent to evaporate from each droplet
    For example peptides, proteins, carbohydrates, small oligonucleotides, synthetic polymers, and lipids
  • 40. Mass Spectrometry
    Nanoelectrospray Ionization (NanoESI)
    where the spray needle has been made very small and is positioned close to the entrance to the mass analyzer. The end result of this rather simple adjustment is increased efficiency, which includes a reduction in the amount of sample needed.
    • Very sensitive
    • 41. very low flow rates
    • 42. Very small droplet size (~5µ)
  • Mass Spectrometry
    Atmospheric Pressure Chemical Ionization (APCI)
    the liquid effluent of APCI is introduced directly into the ionization source. However, the similarity stops there. The droplets are not charged and the APCI source contains a heated vaporizer, which facilitates rapid desolvation/vaporization of the droplets. Vaporized sample molecules are carried through an ion-molecule reaction region at atmospheric pressure.
  • 43. Mass Spectrometry
    Atmospheric pressure photoionization (APPI)
    it generates ions directly from solution with relatively low background and is capable of analyzing relatively nonpolar compounds.
    APPI vaporized sample passes through ultra-violet light.
    APPI is much more sensitive than ESI or APCI.
  • 44. Mass Spectrometry
    Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS)
    the analyte is first co-crystallized with a large molar excess of a matrix compound, usually a UV-absorbing weak organic acid. Irradiation of this analyte-matrix mixture by a laser results in the vaporization of the matrix, which carries the analyte with it. The matrix plays a key role in this technique. The co-crystallized sample molecules also vaporize, but without having to directly absorb energy from the laser. Molecules sensitive to the laser light are therefore protected from direct UV laser excitation.
  • 45. Mass Spectrometry
    Fast Atom Bombardment (FAB)
    Immobilized matrix is bombarded with a fast beam of Argon or Xenon atoms. Charged sample ions are ejected from the matrix and extracted into the mass
    analyzers
    Used for large compounds with low volatility (eg peptides, proteins, carbohydrates)
    Solid or liquid sample is mixed with a non-volatile matrix (eg glycerol, crown ethers, nitrobenzyl alcohol)
  • 46. Mass Spectrometry
    Electron Ionization (EI)
    Energetic process a heated filament emits electrons which are accelerated by a potential difference of usually 70eV into the sample chamber.
    Ionization of the sample occurs by removal of an electron from the molecule thus generating a positively charged ion with one unpaired electron.
    • Produces M+.radical cation giving molecular weight
    • 47. Produces abundant fragment ions
  • Mass Spectrometry
    Chemical Ionization (CI)
    process is initiated with a reagent gas such as methane, isobutane, or ammonia, which is ionized by electron impact.
    High gas pressure in the ionization source is required for the reaction between the reagent gas ions and reagent gas neutrals.
    possible mechanism
    Reagent (R) + e- -> R+ + 2 e-
    R+ + RH -> RH+ + R
    RH+ + Analyte (A) -> AH+ + R
    biologically important molecules (sugars, amino acids, lipids etc.).
  • 48. Mass Spectrometry
    Thermal ionization (TI)
    Samples are deposited on rhenium or tantalum filament
    and then carefully evaporated and sent to mass analyzer.
    used to
    • quantify toxic trace elements in foods.
    • 49. measurement of stable isotope ratio of inorganic elements.
  • Mass Spectrometry
    Mass Analyzer
    Properties of mass Analyzer
    Scan Speed
    Accuracy
    Mass Range
    Resolution
    The range over which a mass spectrometer analyzer can operate.
    is a measure of how close the value obtained is to the true value. The accuracy varies dramatically from analyzer to analyzer depending on the analyzer type and resolution.
    Analyzers are scanned with a regular cycle time from low to high m/z or vice versa.
    A measure of how well a mass
    spectrometer separates ions of different mass
  • 50. Mass Spectrometry
    Mass Analyzer
    • Quadrupoles
    • 51. Quadrupole Ion Trap
    • 52. Linear Ion Trap
    • 53. Double-Focusing Magnetic Sector
    • 54. Quadrupole Time-of-Flight Tandem MS
    • 55. Quadrupole Time-of-Flight MS
  • Mass Spectrometry
    Quadrupoles
    -ions travel parallel to four rods
    - opposite pairs of rods have rapidly alternating potentials (AC)
    - ions try to follow alternating field in helical trajectories
    - stable path only for one m/z value for each field frequency
    Smalll and low cost
    Rmax~ 500
    Harder to push heavy molecule - m/zmax < 2000
  • 56. Mass Spectrometry
    Quadrupole Ion Trap
    The quadrupole ion trap typically consists of a ring electrode and two hyperbolic endcap electrodes. The motion of the ions induced by the electric field on these electrodes allows ions to be trapped or ejected from the ion trap. In the normal mode, the radio frequency is scanned to resonantly excite and therefore eject ions through small holes in the endcap to a detector. As the RF is scanned to higher frequencies, higher m/z ions are excited, ejected, and detected.
  • 57. Mass Spectrometry
    Linear Ion Trap
    The linear ion trap differs from the 3D ion trap as it confines ions along the axis of a quadrupole mass analyzer using a two-dimensional (2D) radio frequency (RF) field with potentials applied to end electrodes. The primary advantage to the linear trap over the 3D trap is the larger analyzer volume lends itself to a greater dynamic ranges and an improved range of quantitative analysis.
  • 58. Mass Spectrometry
    Double-Focusing Magnetic Sector
    the ions are accelerated into a magnetic field using an electric field. A charged particle traveling through a magnetic field will travel in a circular motion with a radius that depends on the speed of the ion, the magnetic field strength, and the ion’s m/z. A mass spectrum is obtained by scanning the magnetic field and monitoring ions as they strike a fixed point detector.
  • 59. Mass Spectrometry
    Quadrupole Time-of-Flight Tandem MS
    Time-of-flight analysis is based on accelerating a group of ions to a detector where all of the ions are given the same amount of energy through an accelerating potential. Because the ions have the same energy, but a different mass, the lighter ions reach the detector first because of their greater velocity, while the heavier ions take longer due to their heavier masses and lower velocity. Hence, the analyzer is called time-of-flight because the mass is determined from the ions’ time of arrival. Mass, charge, and kinetic energy of the ion all play a part in the arrival time at the detector.
  • 60. Mass Spectrometry
    Quadrupole Time-of-Flight MS
    Quadrupole-TOF mass analyzers are typically coupled to electrospray ionization sources and more recently they have been successfully coupled to MALDI. It has high efficiency, sensitivity, and accuracy as compared to Quadrupole and TOF analyzer.
  • 61. Mass Spectrometry
    Detectors used in mass spectrometer
    Faraday Cup
    Photomultiplier Conversion Dynode
    Array Detector
    Charge (or Inductive) Detector
    Electron Multiplier
  • 62. Mass Spectrometry
    Faraday Cup
    A Faraday cup involves an ion striking the dynode (BeO, GaP, or CsSb) surface which causes secondary electrons to be ejected. This temporary electron emission induces a positive charge on the detector and therefore a current of electrons flowing toward the detector.
    not particularly sensitive
    offering limited amplification of signal
    is tolerant of relatively high pressure.
    – Ions are accelerated toward a grounded “collector electrode”
    – As ions strike the surface, electrons flow to neutralize charge, producing a small current that can be externally amplified.
    – Size of this current is related to # of ions in
    – No internal gain -> less sensitive
  • 63. Mass Spectrometry
    Photomultiplier Conversion Dynode
    the secondary electrons strike a phosphorus screen instead of a dynode. The phosphorus screen releases photons which are detected by the photomultiplier. Photomultipliers also operate like the electron multiplier where the striking of the photon on scintillating surface results in the release of electrons that are then amplified using the cascading principle.
    is not as commonly
    Life limit is high as compared to others.
  • 64. Mass Spectrometry
    Array Detector
    detects ions according to their different m/z, has been typically used on magnetic sector mass analyzers.
    The primary advantage of this approach is that, over a small mass range, scanning is not necessary and therefore sensitivity is improved.
  • 65. Mass Spectrometry
    Charge (or Inductive) Detector
    Charge detectors simply recognize a moving charged particle (an ion) through the induction of a current on the plate as the ion moves past
    Detection is independent of ion size.
  • 66. Mass spectrometer
    Electron Multiplier
    • Most important part
    • 67. made up of a series (12 to 24) of aluminum oxide (Al2O3) dynodes
    • 68. Used for increasing potential
    Ions strike the first dynode surface causing an emission of electrons. These electrons are then attracted to the next dynode held at a higher potential and therefore more secondary electrons are generated.
  • 69. Mass spectrometer
    Vacuum in the Mass Spectrometer
    All mass spectrometers need a vacuum to allow ions to reach the detector without colliding with other gaseous molecules or atoms. If such collisions did occur, the instrument would suffer from reduced resolution and sensitivity.
  • 70. Mass spectrometer
    Structural analysis and Fragmentation Patterns
    Mass spectrum
    Graph of ion intensity (relative abundance) along x-axis versus mass-to-charge ratio (m/z) (units
    daltons, Da) along Y-axis
    • Molecular ion (Parent ion)
    • 71. Fragmentation peaks
    • 72. Base peak
    • 73. Isotopic peaks
    .
  • 74. Mass spectrometer
    Molecular ion (Parent ion)
    the peak corresponding to the mol wt of the compound
    The peak of an ion formed from the original molecule by electron ionization, by the loss of an electron, or by addition or removal of an anion or cation and also known as parent peak, radical peak.
  • 75. Mass spectrometer
    Fragmentation peaks
    The peaks observed by fragments of compounds.
    The molecular ions are energetically unstable, and some of them will break up into smaller pieces. The simplest case is that a molecular ion breaks into two parts - one of which is another positive ion, and the other is an uncharged free radical.
    The uncharged free radical won't produce a line on the mass spectrum. Only charged particles will be accelerated, deflected and detected by the mass spectrometer. These uncharged particles will simply get lost in the machine - eventually, they get removed by the vacuum pump.
  • 76. Mass Spectrometry
    Base peak
    The most intense (tallest) peak in a mass spectrum, due to the most abundant ion. Not to be confused with molecular ion: base peaks are not always molecular ion and molecular ion are not always base peaks.
  • 77. Mass Spectrometry
    Fragmentation Patterns
    By using fragmentation pattern we can easily study the structure of a compound.
    • Stevenson’s Rule
    • 78. Homolytic bond cleavage
    • 79. Heterolytic fragmentation
    • 80. Alpha cleavage
    • 81. Beta-cleavage
    • 82. Inductive cleavage
    • 83. Retro Diels-Alder Cleavage
    • 84. McLafferty rearrangement
    • 85. Ortho effect
    • 86. Onimum Reaction
    • 87. CO Elimination
  • Mass Spectrometry
    Stevenson’s Rule
    The most probable fragmentation is the one that leaves the positive charge on the fragment with the lowest ionization energy
    In other words, fragmentation processes that lead to the formation of more stable ions are favored over processes that lead to less-stable ions.
    Cleavages that lead to the formation of more stable carbocations are favored. When the loss of more than one possible radical is possible, a corollary to Stevenson’s Rule is that the largest alkyl radical to be lost preferentially.
  • 88. Mass Spectrometry
    Homolytic bond cleavage
    A type of ion fragmentation in which a bond is broken by the transfer of one electron from the bond to the charged atom, the other electron remaining on its starting atom. The movement of one electron is signified by a fishhook arrow. The fragmentation of a ketone is shown in the figure.
  • 89. Mass Spectrometry
    Heterolytic bond cleavage
    type of ion fragmentation in which a bond is broken by the transfer of a pair of electrons from the bond to the charged atom
    The movement of 2 electrons is signified by a double-barbed arrow and also referred to as charge-induced fragmentation.
  • 90. Mass Spectrometry
    Alpha cleavage
    Alpha cleavage occurs on α-bonds adjacent to heteroatoms (N, O, and S). Charge is stabilized by heteroatom. Occurs only once in a fragmentation (cation formed is too stable to fragment further)
    For example in alcohols, aliphatic ethers, aromatic ethers, cyclic compounds and aromatic ketones etc.
  • 91. Mass Spectrometry
    Beta-cleavage
    Fission of a bond two removed from a heteroatom or functional group, producing a radical and an ion. Also written as β-cleavage. For example allylic fragmentation.
  • 92. Mass Spectrometry
    Inductive cleavage
    If an electron pair is completely transferred towards a centre of positive charge as a result of the inductive effect, shown schematically by the use of a double-headed arrow, then the ion will fragment by inductive cleavage. The figure illustrates this for a radical cation ether.
  • 93. Mass Spectrometry
    Retro Diels-Alder Cleavage
    A multicentered ion fragmentation which is the reverse of the classical Diels-Alder reaction employed in organic synthesis that forms a cyclic alkene by the cycloaddition of a substituted diene and a conjugated diene. In the retro reaction, a cyclic alkene radical cation fragments to form either a diene and an alkene radical cation or a diene radical cation and an alkene. Depending on the substituents present in the original molecule, the more stable radical cation will dominate.
  • 94. Mass Spectrometry
    McLafferty rearrangement
    An ion fragmentation characterised by a rearrangement within a six-membered ring system. The most usual configuration is for a radical cation formed by EI to undergo the transfer of a γ- hydrogen atom to the ionisation site through a ring system as shown here.
    The distonic radical cation so formed can break up by radical-site-induced (α), or charged site-induced fragmentation as shown in the figure. For example ketones, carboxylic acid and esters.
  • 95. Mass Spectrometry
    Ortho effect
    The interaction between substituents oriented ortho, as opposed to para and meta, to each other on a ring system, can create specific fragmentation pathways. This permits the distinction between these isomeric species. The diagram shows a case in which only the ortho isomer can undergo the rearrangement.
  • 96. Mass Spectrometry
    Onium Reaction
    Onium Ion: A hypervalent species containing a non-metallic element such as the methonium ion CH5+. It includes ions such as oxonium, phosphonium, and nitronium ions.
    Mostly observed in cationic fragments containing a heteroatom as charge carrier, e.g.
    oxonium, ammonium, phosphonium and sulphonium ions.
    The onium reaction is not limited to alkyl substituents
    acyl groups can also undergo the onium reaction
  • 97. Mass Spectrometry
    CO Elimination
    Cyclic unsaturated carbonyl compounds and cationic carbonyl fragments
    which resulted from an a-cleavage tend to eliminate CO .
    If there is more than one CO group present sequential elimination of all CO
    groups is possible.
    From carbonyl compounds CO elimination reaction takes place like in aldehyde, ketones and phenols etc
  • 98. Mass Spectrometry
    Rules for interpretation of mass spectrum
    • DBR Calculations
    • 99. Nitrogen Rule
    • 100. Isotopic effect
  • Mass Spectrometry
    DBR Calculations
    Double bond or ring calculations tell us about how many rings or double bonds are present in a compound.
    DBR= C-H/2+N/2+1
    C= number of carbon atoms
    H= number of hydrogen atoms
    N= number of nitogen atoms
  • 101. Mass Spectrometry
    Nitrogen Rule
    • If a compound contains an even number of nitrogen atoms (or no nitrogen atoms), its molecular ion will appear at an even mass number.
    • If, however, a compound contains an odd number of nitrogen atoms, then its molecular ion will appear at an odd mass value.
    • This rule is very useful for determining the nitrogen content of an unknown compound.
  • 102. Mass Spectrometry
    Isotopic effect
  • 103. Mass Spectrometry
    Mass spectra (examples)
    Alkanes
    Strong M+ (but intensity decreases with an increase of branches.
    Carbon-carbon bond cleavage
    loss of CH units in series: M-14, M-28, M-42 etc
  • 104. Mass Spectrometry
    Alkanes
  • 105. Mass Spectrometry
    Cycloalkanes
    Strong M+, strong base peak at M-28 (loss of ethene)
    A series of peaks: M-15, M-28, M-43 etc
    Methyl, ethyl, propyl with an additional hydrogen give peaks
  • 106. Mass Spectrometry
    Alkenes
    Strong M+
    Fragmentation ion has formula CnH2n+ and CnH2n-1
    -Cleavage
    A series of peaks: M-15, M-29, M-43, M-57 etc
  • 107. Mass Spectrometry
    Alkynes
    Strong M+
    Strong base peak at M-1 peak due to the loss of terminal hydrogen
    Alpha cleavage
  • 108. Mass Spectrometry
    Aromatic Hydrocarbons
    Strong M+
    Loss of hydrogen gives base peak
    McLafferty rearrangement
    Formation of benzyl cation or tropylium ion
  • 109. Mass Spectrometry
    Alcohols
    M+ weak or absent
    Loss of alkyl group via a-cleavage
    Dehydration (loss of water) gives peak at M-18
  • 110. Mass Spectrometry
    Phenols
    Strong M+
    M-1 due to hydrogen elimination
    M-28 due to loss of CO
    M-29 due to loss of HCO (formyl radical)
  • 111. Mass Spectrometry
    Ethers
    M+ weak but observable
    Loss of alkyl radical due to a-cleavage
    B-cleavage( formation of carbocation fragments through loss of alkoxy radicals)
    C-O bond cleavage next to double bond
    Peaks at M-31, M-45, M-59 etc
  • 112. Mass Spectrometry
    Aldehyde
    M+ weak, but observable (aliphatic)
    Aliphatic : M-29, M-43 etc
    McLafferty rearrangement is common gives the base peak
    A-cleavage
    B-cleavage
  • 113. Mass Spectrometry
    Aldehyde
    M+ strong (aromatic)
    Aromatic: M-1 (loss of hydrogen)
    M-29 (loss of HCO)
    McLafferty rearrangement is common
    A-cleavage
    B-cleavage
  • 114. Mass Spectrometry
    Ketones
    Strong M+
    A series of peaks M-15, M-29, M-43 etc
    Loss of alkyl group attached to the carbonyl group by a-cleavage
    Formation of acylium ion (RCO+)
    McLafferty rearrangement
  • 115. Mass Spectrometry
    Esters
    M+ weak but generally observable
    Loss of alkyl group attached to the carbonyl group by a-cleavage
    Formation of acylium ion (RCO+)
    McLafferty rearrangement
    Acyl portion of ester OR+
    Methyl esters: M-31 due to loss of OCH3
    Higher esters: M-32, M-45, M-46, M-59, M-60, M-73 etc
  • 116. Mass Spectrometry
    Carboxylic acids
    Aliphatic carboxylic acids:
    M+ weak but observable
    A-cleavage on either side of C=O
    M-17 due to loss of OH
    M-45 due to loss of COOH
    McLafferty rearrangement gives base peak
  • 117. Mass Spectrometry
    Aromatic carboxylic acids:
    M+ Strong
    A-cleavage on either side of C=O
    M-17 due to loss of OH
    M-18 due to loss of HOH
    M-45 due to loss of COOH
    McLafferty rearrangement gives base peak
  • 118. Mass Spectrometry
    Amines
    M+ weak or absent
    Nitrogen rule obey
    A-cleavage
  • 119. Mass Spectrometry
    Nitriles
    M+ weak but observable
    M-1 visible peak due to loss of termiminal hydrogen
  • 120. Mass Spectrometry
    Nitro Compounds
    M+ seldom observed
    Loss of NO+ give visible peak
    Loss of NO2+ give peak
  • 121. Mass Spectrometry
    Alkyl chloride and alkyl bromides
    Strong M+2 peak
    For Cl M/M+2 = 3:1
    F or Br M/M+2 = 1:1
    A-cleavage
    Loss of Cl or Br
    Loss of HCl or HBr
  • 122. Mass Spectrometry
    Alkyl chloride
  • 123. Mass Spectrometry
    Applications of Mass Spectrometry
    The technique has both quantitative and qualitative uses. These include identifying unknown compounds, determining the isotopic composition of elements in a molecule, and determining the structure of a compound by observing its fragmentation. Followings are the main applications
  • Mass Spectrometry
    Toxicity of Toothpastes
    DEG (diethylene glycol) which is a toxic chemical and usually present in Chinese toothpastes.
    Measuring nanoparticle size
    Mass spectrometry is used to measure nanoparticle size like platinum nanoparticles which is used as catalyst.
    Once size of a sphere is measured, its density is also calculated.
    Pharmacokinetics
    Pharmacokinetics is often studied using mass spectrometry because of the complex nature of the matrix (often blood or urine) and the need for high sensitivity to observe low dose and long time point data.
  • 132. Mass Spectrometry
    Protein characterization
    Mass spectrometry is an important emerging method for the characterization of proteins. The two primary methods for ionization of whole proteins are electrospray ionization (ESI) and (MALDI).
    Space exploration
    Mass spectrometers are also widely used in space missions to measure the composition of plasmas. For example, the Cassini spacecraft carries the Cassini Plasma Spectrometer (CAPS),[44] which measures the mass of ions in Saturn's magnetosphere.
    Isotope dating and tracking
    Mass spectrometry is also used to determine the isotopic composition of elements within a sample. Differences in mass among isotopes of an element are very small, and the less abundant isotopes of an element are typically very rare, so a very sensitive instrument is required. These instruments, sometimes referred to as isotope ratio mass spectrometers (IR-MS).
  • 133. Mass Spectrometry
    Molecular weight
    Molecular weight can be determined by mass spectrometry.
    Actual number of carbons, hydrogen, oxygen etc
    By using relative intensities(peak hight), we can easily calculated the actual numbers of C,H,O etc atoms.
    Bonding
    Bonding can be studied by fragmentation patterns for example, beta cleavage is possible only if double bonds or heteroatom present.
    Reaction mechanism
    Mass spectrometry is best technique to study reaction mechanism and intermediates produced in reaction, for example, in carboxylic acid and alcohols a peak at M-18 indicates that water is produced.
  • 134. Mass Spectrometry
    Determination of Elements
    Bulk materials such as steel or refractory metals, elements are determined by low-resolution glow-discharge mass spectrometry. High-resolution GDMS has been used to study semiconductor materials. GDMS is considered virtually free of matrix effects.
    Detection limits in ICPMS as in Table
  • 135. Mass Spectrometry
    Species Analysis
    Heavy metals in the environment are stored in complexes with humic acids, can be converted by microbes in different complexes, and can be transported in live animals and humans. This applies to many elements such as lead, mercury, arsenic, astatine, tin and platinum
    For example, tin and lead alkylates established in soil, water or muscle tissue by GC / MS after exhaustive alkylation or thermal spray, and ICP-LC/MS API methods.
  • 136. Mass Spectrometry
    Environmental Chemistry
    the analysis of trace elements and compounds in environmental samples like air, water, soil etc because of its detection power, specificity and structural analysis functions
    Generally, sample preparation is at least one type of chromatography coupled with MS either offline or online like GCMS
  • 137. Mass Spectrometry
    References
    • Dictionary of Mass Spectrometry, A.I. Mallet and S. Down, 2009
    • 138. Introduction to spectroscopy, Donald L. Pavia
    • 139. Hand book of spectroscopic data, B.D.Mistry.
    • 140. Comprehensive analytical chemistry.
    • 141. . Handbook of Spectroscopy, by G. Gauglitz and T. Vo-Dinh
    • 142. Instant notes of Analytical chemistry, D.Kealey.
    • 143. Modern Analytical Chemistry, David Harvey.
    • 144. The Basics of Spectroscopy, David.W.Ball.
    • 145. Encyclopedia of Analytical Chemistry Applications, Theory and Instrumentation Edited by R.A.Meyers
    Handbook of Analytical Techniques edited by Helmut Giinzler and Alex Williams 1st Edition 2001
    • Encyclopedia of Spectroscopy and Spectrometry part 2(M-Z) Edited By john C. lindon, George E. Tranter and John L. Holmes
  • Thank You !
    Mass Spectrometry
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