Mass Spectrometry: underlying concepts and applications. Marek Tulej. From Ultrafast to Ultracold: Modern Topics and Methods in Physical Chemistry

Transcription

1 From Ultrafast to Ultracold: Modern Topics and Methods in Physical Chemistry Mass Spectrometry: underlying concepts and applications Marek Tulej 1

2 Organisation Course 7 weeks x 2 hours Language Englisch Manuscript Copy of presented material will be distributed References to books and papers pertaining to the various subject Exam Englisch or German 2

3 Mass spectrometry: underlying concepts and applications Outline: 1. Concepts and trends in mass spectrometry 2h 2. Ion sources 2h 3. Mass analysers 8h: Magnetic and electric fields analysers 2h Rf mass spectrometry, ion guiding and trapping 2h Time of flight mass spectrometry 4h 4. High resolution mass spectrometry 2h 3

4 Literature J. Th. Watson & O. D. Sparkaman, Introduction to mass spectrometry, Wiley, E. Hoffmann, V. Stroobant, Mass Spectrometry, Wiley, 2007 J. S. Becker, Inorganic Mass Spectrometry, Wiley, 2007 F. Hillenkamp, J. Peter-Katalinic, MALDI MS, Wiley 2007 P.H. Dawson, Quadrupole Mass Spectrometry and ist application, Elsevier 1976 R. E. March, J.F.J. Todd, Practical Aspects of Ion Trap Mass Spectrometry I, II, III, CRC Series, Modern Mass Spectrometry, 1995 Dietze, H.-J. Laser Ionization Mass Analysis, Chemical Analysis Series Vol. 124, Wiley, 1993 Ch. E. Melton, Principles of Mass spectrometry and Negative Ions, Marcell Dekker, NY H. Budzikiewicz, Massenspectrometrie, 1980 E. Schröder, Massenspectrometrie; Begrife und Definitionen F.W. McLafferty, F. Turecek, Interpretation von Massenspektren Ion optics: M. Reiser, Theory and Design of Charged Particle Beams,

5 Journals International Journal of Mass Spectrometry and Ion Processes Analytical, Bioanalytical Chemistry Mass Spectrometry Review Rapid Communication in Mass Spectrometry Mass SpectrometryBulletin Organic Mass Spectrometry Biological Mass Spectrometry Review of Scientific Instruments Measurements Science and Technology 5

6 Internet Peridic table Base peak Table of nucleides 6

7 Mass spectrometry Analytical method: sensitive detection and mass measurement of atoms, molecules, and large particles Leading method in analytical chemistry Biochemical problems: proteome, metabolome, drug discovery, metaboloism Pollution control, food control, forensic science, natural products, process monitoring Reaction kinetics, ion-molecule reactions Inorganic chemical analysis Atomic physics, reaction physics Application in space: planetary atmospheres, exospheres, solar wind, composition of planetary material 7

8 Chemical probing with high spatial resolution

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13 Meteoritic studies of early solar system e.g., laser spot Mg Si Ca Al 13

14 Space 14

15 The matter of mass spectrometry Molecules: neutral species composed of atoms connected according to valence rules, having an even number of electrons Radicals: neutral species composed of atoms connected according to valence rules, having an odd number of electrons Ions: species that have either a positive or negative charge, composed of atoms connected according to valence rules, having either an odd number or even number of electrons Atoms (isotopes) and their ions Charged particles, large clusters, (e.g., virus) 15

16 Conceptual illustration of the mass spectrometer <1970 gaseous samples >1970 desorption/ionization techniques e.g., fast atom bombardment FAB >1980s: ESI, MALDI separation of ions, according to their mass to charge ratio m/q by controlling of ion energy, momentum or ion spatial location 16

17 Principle of operation of mass spectrometer 17

18 Mass spectrum Atoms detection: the elemental composition Steinless steel Mass resolution m/dm: 400 Mass range: 250 Detection limits ~ppm Abundances of the elements close to quoted ones by NIST 18

19 Mass spectrum Molecule detection: 19

20 Characteristics Mass range: the maximum mass/charge (m/q) ratio amenable for analysis Mass resolution: the ability to separate two neighboring mass ions Abundance sensitivity: the number obtained by dividing the abundance of the large peak over the abundance of the next mass peak in the background Detection sensitivity: the smallest amount of analyte which can be detected at certain defined confidence level Mass accuracy: the measured error in m/q to accurate m/q 20

21 Definition Mass resolution (resolving power): information on the size of the mass difference m of two ion beams with masses m and m+ m in order to separate and detect both ion beams clearly. Below two definitions are demonstrated: valley and peak width ones. 10 valley definition is used for magnetic sector spectrometer 50 % value definition is used for quadrupole and time of flight mass spectrometers 21

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23 Example Low resolution: High resolution: >

24 Abundance sensitivity Here the abundance of B will be overestimated due to the peak tailing from the abundant ion peak Very important for the quantitative studies of abundances of trace elements, or studies of isotopic ratio s. 24

25 mass resolution sensitivity Over years: Thomson Dempster Aston Aston Marshall et al. 800 yoctomoles (480 molecules): concentration of peptide by desorption/ionizationon silicon substrate accuracy of measurements of atomic masses: 10-9 u mass range: DNA ions of 10 8 Da viral particles 40.5 MDa 25

26 Comparison of different ion separation system Abundance sensitivity

27 Atomic mass unit Atomic mass unit [amu]: 12 C 1 amu = m a ( 12 C)/12 = kg before 1961 the oxygen atom 16 O was proposed: 1 amu= ma( 16 O)/16 Mass spectrometric measurements provide infor on mass to charge ratio, m/q. In SI system of units is defined as amu/q 0, where amu is atomic mass unit, and q0 is unit charge Thomson [Th]: 1Th= 1 amu/q 0 = 1 u/e= x10-8 kgc -1 Dalton [Da], 1Da=1 amu (bio-sciences and medicine) An advantage of the definition of mass unit is that the mass of an atom or molecule can be characterized by a full number A, which is equal to the number of ncleons: m a ~ A x 1amu 27

28 Mass spectrometry of elements Mass number, A: A=Z+N, Z-number of protons; N-number of neutrons Isotopes of a chemical element are nuclides with the same number of protons (N) e.g., 35 Cl, 37 Cl 54 Fe, 56 Fe, 57 Fe, 58 Fe 20 elements are mono-isotopic 21 elements have two stable isotopes for the majority of the chemical elements more than 3 isotopes exists There 237 stabile isotopes (in total number 3000); last 180 Ta was discovered in1955 The isotopic abundances are not constant and depend on sample studied e.g., 13 C/ 12 C= photosynthesis = Earth gas, oil 28

29 Detection of isotopes Isotopes of lead Pb A qualitative identification of isotopes is based on their abundance pattern Terrestrial isotopic abundances! Isobaric interferences in measurement of elements can occur because of abundance of a few elements of the same mass in the sample e.g., 50 Ti, 50 V, 50 Cr. 29

30 Mass defect F.W. Aston (1923): Fand kleine Abweichungen vom Gesetz der ganzen Massenzahlen. > Costa (1925): Erste Studie dieser Abweichungen mit einem Instrument vom Aston-Typ. 1H genau bestimmt, Vergleich mit 4 He, 6 Li, 7 Li, 12 C, 14 N. Genauigkeit der Massenbesstimmung 1 in > F.W. Aston (1927): Systematische Studie der Abweichungen mit einem Instrument mit Auflösung m/δm =600 und einer Genauigkeit von 1/ O als Massestandard. Bestimmung des Massendefekts: (M A)/A. 30

31 Brainbridge (1930): Wien mass filter combined with 180 B deflector Prove of Einstein equvalence principle E= mc 2 1 H + 7 Li 2 4 He Mass defect-nuclear binding energy Massenspektrographen für Verwendung eines Wienfilters (gekreuztes E und B-Feld) zusammen mit einem 180 Magneten. S 1, S 2 und S 3 : Kollimatorschlitze P 1 und P 2 : Kondensatorplatten für das elektrische Feld des Wien- Filters Ionennachweis mit Photoplatte 2 H Massenbestimmung, und andere Isotopenhäufigkeiten: Zn, Ge, Te 31

32 Phys. Rev. 44 (1933)

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34 Isotope Ratio Mass Spectrometry δ- notation Standard for 13 C/ 12 C: belemnite fossil Peedee formation, South Carolina, USA ε notation 34

35 Hydrogen/Deuterium 35

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37 Example: CH 3 Cl Average mass, nominal mass, monoisotopic mass Cl is mixture of two isotopes 35, 37 with 75.77% and 24.23% natural abundances, respectively, similarly C and H possess isotopes but at smaller abundances Average mass take into account balanced average of elements x = Da Monoisotopic mass is x = and is calculated using the exact masses of the predominant isotope of each element Nominal mass is taking integer mass of most abundand isotope of each element : 12+3x1+35= 50 37

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39 Isotopic analysis Assuming natural isotopic distribution of elements one can evaluate molecular chemical composition: Br 2 can be formed from following combination of elements: 39

40 In general for n atoms of one element with isotopic masses X A, Y A, and abundances I XA, I YA For molecule containing n atoms of one elements with two isotopes : 40

41 Isotopic template Other example for molecule with two elements and two isotopes: 41

42 Precission of atomic mass measurements due to improvements of high resolution 42

43 Accurate masses Measurements with high resolution enable presized determination of the elementar and isotopic composition 43

44 Mass resolution by comparison 44

45 Interferences

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48 Mass spectrometry: historical 1886 E. Goldstein: anode rays (positive gas phase ions) in gas discharge 1897 J.J. Thomson: mass/charge ratio of electrons 1897 W. Wien: analysis of anode rays by magnetic deflection: -> positive charge of the rays magnet-electrostatic deflectros (EB), radiofrequency (rf) analysers, time of flight, reflectron, Fourier transform (FT) high resolution analysers T. Tanaka, M. Karas, F. Hillenkamp: Matrix assisted laser desorption mass spectrometry (MALDI) 1988 J. Fenn: Electrospray (ESI) 1999 A.A. Makarov: orbitrap analysers 48