Isotope in ms (OAN MUHAMMAD SAHITO)

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My name is Oan Sahito, This presentation included info about isotopes observation using mass spectrometry.
email# oan.sahito@gmail.com

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Isotope in ms (OAN MUHAMMAD SAHITO)

  1. 1. 8/28/2014 1
  2. 2. 2 Presented by: oan.sahito@gmail.com
  3. 3.  3 OUTLINES  INTRODUCTION  BASIS OF SEPARARION  IONIZER, ANALYZER AND DETECTOR TYPES  ISOTOPES AND OBSERVATION OF ISOTOPES  CLASSIFICATION OF ISOTOPES  SPECTRAS  ISOTOPIC ABUNDANCE  CONCLUSION  REFERENCES  ACKNOWLEDGEMENTS
  4. 4.  It subjects vaporized molecules to bombardment by a stream of high-energy electrons, converting these molecules to ions 8/28/2014 4 INTRODUCTION
  5. 5.  These ions are then accelerated in an electric field The accelerated ions are then separated according to their mass-to-charge ratio in a magnetic or electric field 8/28/2014 5 BASIS OF SEPARATION
  6. 6. 8/28/2014 6 INSTRUMENTAL DIAGRAM
  7. 7.  8/28/2014 7 Ionizer Sample introduction/ionization method: Ionization method Typical Analytes Sample Introduction Mass Range Method Highlights Electron Impact (EI) Relatively small volatile GC or liquid/solid probe to 1,000 Daltons Hard method versatile provides structure info Chemical Ionization (CI) Relatively small volatile GC or liquid/solid probe to 1,000 Daltons Soft method molecular ion peak [M+H]+ Electrospray (ESI) Peptides Proteins non-volatile Liquid Chromatography or syringe to 200,000 Daltons Soft method ions often multiply charged Fast Atom Bombardment (FAB) Carbohydrates Organometallics Peptides nonvolatile Sample mixed in viscous matrix to 6,000 Daltons Soft method but harder than ESI or MALDI Matrix Assisted Laser Desorption (MALDI) Peptides Proteins Nucleotides Sample mixed in solid matrix to 500,000 Daltons Soft method very high mass
  8. 8.  8/28/2014 8 Ion Analyzer Analyzer System Highlights Quadrupole Unit mass resolution, fast scan, low cost Sector (Magnetic and/or Electrostatic) High resolution, exact mass Time-of-Flight (TOF) Theoretically, no limitation for m/z maximum, high throughput Ion Cyclotron Resonance (ICR) Very high resolution, exact mass, perform ion chemistry Tandem Mass Spectrometry (MS/MS) Molecular structure determination
  9. 9. Detector, Vacuum Detector Convert the beam of ions in an electrical signal that can be processed, stored, displayed and recorded in many ways. Vacuum System MS require the high vacuum is maintained in all spectrometer components (except signal processing) Electron Multiplier (most commonly used) Faraday cup Photographic plates Scintillation type Other:
  10. 10.   Mass spectrometers analyze gas-phase ions, not neutral molecules  Neutrals don’t respond to electric and magnetic fields  If a molecule cannot ionize, MS cannot help  MS is not a “magic bullet” technique  MS can describe atomic composition of an ion  Connectivity of the atoms is much more challenging  Although MS requires a vacuum, it cannot be performed in a vacuum of information  Deriving useful information from MS data often requires some knowledge of the system under investigation8/28/2014 10 IMPORTANT POINTS TO REMEMBER
  11. 11. Francis William Aston "For his discovery, by means of his mass spectrograph, of isotopes, in a large number of non-radioactive elements, and for his enunciation of the whole-number rule8/28/2014 11 1922 Nobel Prize
  12. 12.  Isotopes can be classified as Mono-isotope Di-isotope Poly-isotope 8/28/2014 12 Isotopic Classification of the Elements
  13. 13.  Monoisotopic Elements . 8/28/2014 13
  14. 14. 8/28/2014 14 Among 82 naturally occurring stable elements, 20 elements do exist in the form of only one single naturally occurring stable isotope. Among the monoisotopic elements, Fluorine (19F), Sodium (23Na), Phosphorus (31P), and Iodine (127I) belong to the more prominent examples in organic mass spectrometry.
  15. 15. Methyl Floride 15
  16. 16.  16 Nonetheless, there are many more such as 9Be, 27Al, 55Mn, 59Co, 75As, 93Nb, 103Rh, 133Cs, and 197Au
  17. 17.  The monoisotopic elements are also referred to as M, A or X elements. If radioactive isotopes were also taken into account, not a single monoisotopic element would remain. 8/28/2014 17
  18. 18. 8/28/2014 18 Di-isotopic Elements
  19. 19.  Several elements exist naturally in two isotopes. These elements can even be sub-classified into those having ONE isotope that is 1 u heavier than the most abundant isotope. The first group has been termed M+1 elements. 8/28/2014 19
  20. 20. 8/28/2014 20 Prominent examples of M+1 elements are Hydrogen (1H, 2H = D), Carbon (12C, 13C), and Nitrogen (14N, 15N).
  21. 21. 8/28/2014 21 Those having one isotope that is 2 u heavier than the most abundant isotope They have been termed M+2 elements, respectively
  22. 22. 8/28/2014 22 Elements such as chlorine, bromine, oxygen, sulfur, and silicon, can be dealt with as X+2 elements
  23. 23. Silicon 23
  24. 24. 8/28/2014 24 Among the X+2 elements, Chlorine (35Cl, 37Cl), Bromine (79Br, 81Br) are relatively common but Copper (63Cu, 65Cu), Gallium (69Ga, 71Ga), Silver (107Ag, 109Ag), Indium (113In, 115In), and antimony (121Sb, 123Sb) also belong to this group.
  25. 25. 84-49=35 49-14=35 A+2 peak with fragment of 35 indicates Cl presence. 25
  26. 26. Chlorine 35Cl (P= .75) 37Cl (P= .25) Ratio 3:1 Probability : [M+] / [M + 2] = 0.75 / 0.25 = 3 / 1 100 : 33 8/28/2014 26
  27. 27.  8/28/2014 27 Methyl Bromide: An example of A+2 isotopes The ratio of peaks containing 79Br and its isotope 81Br (100/98) confirms the presence of bromine in the compound.
  28. 28.  A-1 Peak 8/28/2014 28 If we do not restrict our view to the elements, one should add the class of A–1 elements with one minor isotope of 1 u lower mass than the most abundant one
  29. 29. 8/28/2014 29 The elements Lithium (6Li, 7Li), Boron (10B, 11B), and Vanadium (50V, 51V) come along with a lighter isotope of lower abundance than the heavier one and thus, they can be grouped together as X–1 elements.
  30. 30. 30
  31. 31.  BORON 31
  32. 32. 8/28/2014 32 Poly-isotopic Elements
  33. 33.  The majority of elements are grouped as poly- isotopic elements because they consist of three or more isotopes showing a wide variety of isotopic distributions. 8/28/2014 33
  34. 34. 34
  35. 35. Tungsten Index MS-fragmentation 8/28/2014 35
  36. 36.  Isotopic abundances are listed either as their sum being 100% or with the abundance of the most abundant isotope normalized to 100%. The custom of reporting mass spectra normalized to the base peak. 8/28/2014 36 Representation of Isotopic Abundance
  37. 37. Isotopic abundances for Carbon containing compounds Relative ratio: [M+1]+ / [M+ ] = n(0.989)n-1 (0.011) / (0.989)n = n (0.011) / (0.989) = n (0.0111) In percentage: n x 1.1 % 8/28/2014 37
  38. 38. Isotopic abundances for other common nuclei For 15N: [M+1]+ / [M]+ => n x 0.36% For 33S: [M+1]+ / [M]+ => n x 0.80% For 18O: [M+2]+ / [M]+ => n x 0.20% For 34S: [M+2]+ / [M]+ => n x 4.42% 8/28/2014 38
  39. 39.  Have seen that for Cl and Br, having two common isotopes, two radical cation peaks produced. What about other elements having more than one isotope? We know what the isotopes are and their natural occurrence. For the M+1 peak, one atom must be using an isotope heavier by one. 8/28/2014 39 Molecular Peaks, M+1
  40. 40.  8/28/2014 40 We will use isotopic occurrence data for H, C, O for the M + 1 peak.
  41. 41. Technique to obtain molecular formula using intensities of M, M+1, M+2 peaks. Consider the M+1 peak, nominal mass + 1. If we know the formula we should be able to calculate the relative intensity of that peak due to the contributions from each of the atoms present. Here are the major contributors to M+1. Example. Given the data. Peak Intensity 150 (M) 100 151 (M+1) 10.2 152 (M+2) 0.88 Looking at M+2 there is no Br, Cl or S. There could be oxygen. Even mass for M means there could only be even number of Nitrogen 8/28/2014 41
  42. 42. Technique to obtain molecular formula using intensities of M, M+1, M+2 peaks. Example. Given the data. Peak Intensity 150 (M) 100 151 (M+1) 10.2 152 (M+2) 0.88 Equations M+1: (1.11% x # of C) + (0.38 x # of N+ small contributions from O M+2: (0.20 x # of O) + (1.1 x # of C)2/200 We can have 0 or 2 nitrogens. Even number. We can have 0,1,2,3,4 oxygens. 0.88/0.2 < 5 Can have 0,1,2,3,4,5,6,7,8,9 carbons. 10.2/1.11 <10 Find molecular formulas having reasonable M+1 peaks M+1 M+2 C7H10N4 9.25 0.38 C8H10N2O 9.61 0.61 C9H10O2 9.96 0.84 C9H14N2 10.71 0.52 Examine reasonable formulae. Calculate M+1, M+2 peaks 8/28/2014 42
  43. 43. Example. Identify this molecule m/e Abundance 1 <0.1 16 1.0 17 21 18 100 19 0.15 20 0.22 Due to heavier isotopes Molecular radical ion Ejection of an H H2O 8/28/2014 43
  44. 44. Example 2 m/e Abundance 12 3.3 13 4.3 14 4.4 15 0.07 16 1.7 28 31 29 30 31 32 100 89 1.3 0.21 Heavier isotopes parent H ejection Oxygen carbon CH2O 8/28/2014 44
  45. 45.   The “exact mass” feature in ChemDraw will give you a monoisotopic mass  Not always correct for complex isotope patterns  Two freeware apps are available from MSF website “Links” page  These can be used to predict the entire isotopic pattern as an exportable image  MS-Search program on GC-MS computer can be used to retrieve mass spectra from NIST’02 library 8/28/2014 45 Some useful software tools
  46. 46. 46 46 Mass spectrometry is very useful technique for identification of ISOTOPES, through different ionizaion sources for different molecules It is observed through study that isotope of some elements are 1unit heavier while others are 2unit heavier than most abundant isotope hence shown as M+1 and M+2 peaks respectively in Mass Spectra. Isotopes 1unit lighter observed as M-1 peak in Mass Spectra. Observation of poly-isotopes as M+3 and so on.
  47. 47.  REFERENCES 1. MASS SPECTROMETRY BY JURGEN H GROSS, SPRINGER INTERNATIONAL EDITION 2. NIST WEB BOOK http://webbook.nist.gov 3. LECTURE SLIDES OF DR SHAHABUDDIN MEMON 4. WIKIPEDIA 5. SPECTROMETRIC IDENTIFICATION OF OGANIC COMPOUNDS BY ROBERT M.SILVERSTEIN 7th EDITION 2005 6. http//www.chemistry.ccsu/glagovich/teaching/316/ms/ 7. GOOGLE IMAGES FORM www.google.com 47
  48. 48. 48

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