HANDOUT_CH3F2_MassSpectrometry_Barrow_Lecture 1_2023-2024.pdf
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CH3F2 (Advanced Analytical Chemistry) Mass Spectrometry: Basics Dr. Mark P. Barrow Introduction Contact information Dr. Mark P. Barrow Reader based within Department of Chemistry Research: FT-ICR mass spectrometry for complex mixture analysis (e.g. energy, environmental, and archaeological) M.P.Barr...
CH3F2 (Advanced Analytical Chemistry) Mass Spectrometry: Basics Dr. Mark P. Barrow Introduction Contact information Dr. Mark P. Barrow Reader based within Department of Chemistry Research: FT-ICR mass spectrometry for complex mixture analysis (e.g. energy, environmental, and archaeological) [email protected] Traffic lights Green: must know (basic material) Amber: should know (moderate material) Red: useful but unlikely to be on the exam (advanced material) Moodle https://moodle.warwick.ac.uk/course/view.php?id=57391 Quizzes Workshop Outline of mass spectrometry section of CH3F2 Principles (Dr. Mark Barrow) Applications (Prof. Peter O’Connor) Books “Mass Spectrometry” James McCullagh and Neil Oldham Oxford Chemistry Primers ISBN: 9780198789048 “Mass Spectrometry: Principles and Applications” Edmond de Hoffmann and Vincent Stroobant Wiley ISBN: 978-0-470-03310-4 Books “Mass Spectrometry: A textbook” Jürgen Gross Springer ISBN: 978-3-319-54397-0 https://link.springer.com/book/10.1007/978-3-319-54398-7 Nobel Prizes J. J. Thomson (1906) F. W. Aston (1922) H. G. Dehmelt (1989) J. B. Fenn (2002) W. Paul (1989) K. Tanaka (2002) Fundamentals What is mass spectrometry? What is mass spectrometry? Analyzes sample: single compound or mixture of compounds Needs gas-phase ions Measures: Mass Mass-to-charge ratio (m/z) m/z m/z is the mass-to-charge ratio m is the mass, measured in unified atomic mass unit (u) or daltons (Da) 1 u or Da = 1.66053906660 × 10−27 kg John Dalton FRS (1766-1844) m/z z is the number of charges q is the total charge in coulombs (C) Calculated by: q = z × e where e is the elementary charge (1.602176634 × 10−19 C) Charles-Augustin de Coulomb 1736-1806 Mass spectra Mass spectrometers measure signal (“intensity” or “abundance”) as a function of m/z “Spectrum” vs. “spectra” Singular: mass spectrum Plural: mass spectra Also… “Mass Spectrometry: A textbook,” Jürgen Gross, Springer ISBN: 978-3-319-54397-0 Example mass spectrum Relative intensity 100% 1.5E6 Absolute intensity "Mass Spectrometry," James McCullagh and Neil Oldham, Oxford Chemistry Primers, ISBN: 9780198789048 Components of a mass spectrometer Sample inlet Ionization method Analyzer Vacuum system Detection Data system Chromatography and mass spectrometry Total ion chromatogram (TIC) Mass spectra Components of a mass spectrometer Sample inlet Ionization method Analyzer Vacuum system Detection Data system Vacuum Vacuum needed for ions to pass through mass spectrometer Need to avoid collisions between ions and gas Atmospheric pressure (1 Atm) = 1.013 bar = 1013 mbar = 101325 Pa = 760 Torr Mass and m/z 1 mass unit: amu: 1/16 of 16O (pre-1961) u: 12C = 12.0000 u (1961 to present) dalton, Da Mass-to-charge ratio m/z thomson, Th (not commonly accepted) Isotopes Mass defect and isotopes: carbon 12.000000 Da 98.93% 13.003355 Da 1.07% Mass defect Mass defect Carbon monoxide, CO Nitrogen, N2 Carbon = “12 Da” Oxygen = “16 Da” Nitrogen = “14 Da” CO = “28 Da” N2 = “28 Da” Mass defect Carbon monoxide, CO Nitrogen, N2 Carbon = 12.000000 Da Oxygen = 15.994915 Da Nitrogen = 14.003074 Da CO = 27.994915 Da N2 = 28.006148 Da CO+ = 27.994366 Da N2+ = 28.005599 Da (Mass of an electron = 0.000548 Da) Isotopes Variants of a particular element Same number of electrons and protons Different number of neutrons Therefore have different mass-to-charge ratio Will separate in a mass spectrometer “Isotopologues” Same molecular formulae but differing by isotope content Carbon, natural abundance: 98.9% 12C 1.1% 13C https://www.wavemetrics.com/products/igorpro/gallery/user_whittal Calculating isotope patterns Can calculate isotope patterns: N! P(i ) = p i (1 - p ) N -i i!( N - i )! N= number of atoms i = ith isotope p = probability of being heavy isotope (e.g. 13C) Yergey, J. A. Int. J. Mass Spectrom. Ion Physics, 1983, 52, 337-349. Rockwood, A. L.; Van Orden, S. L.; Smith, R. D. Anal. Chem. 1995, 67, 2699-2704. Example mass spectrum Monoisotopic peak Isotopologues "Mass Spectrometry," James McCullagh and Neil Oldham, Oxford Chemistry Primers, ISBN: 9780198789048 Isotopologues C5 12 C5 C60 13C has a natural abundance of approximately 1.1% ~66% 12C 13C 4 1 12 ~5.5% ~99% C3 13C2 C90 ~132% (100%) C120 Use of isotope ratios (PDB: Pee Dee Belemnite, a fossil from South Carolina, USA, used as a standard) “Mass Spectrometry: A textbook,” Jürgen Gross, Springer ISBN: 978-3-319-54397-0 Performance Mass accuracy Figure of merit associated with measurement; measured in parts per million (ppm) Better mass accuracy allows user to have higher confidence in assignment Lower values are better Examples: TOF typically 3-5 ppm FTICR typically ≤ 1 ppm Mass accuracy Number of possible assignments (molecular formulae) for a peak increases with: m/z error tolerance “Mass Spectrometry: A textbook,” Jürgen Gross, Springer ISBN: 978-3-319-54397-0 Resolving power “...may be characterized by giving the peak width... for at least two points on the peak, specifically at fifty percent and at five percent of the maximum peak height.” (IUPAC Gold Book) Allows user to observe closely spaced peaks “Full width at half maximum” (FWHM) typically used Higher values (narrower peaks) are better Examples: ≈10,000 (FWHM) for TOF ≈500,000+ (FWHM) for FTICR Resolving power Anal. Chem., 2002, 74, 252A-259A Examples Isotopic fine structure Substance P: C63H98N18O13S 1346.728146 Da Resolving powers Quadrupole = ~2000 Q-TOF = ~50,000 Orbitrap = ~200,000 FTICR = ~500,000 – 10,000,000 Resolving Power ~450,000 13C Δm = 0.86 mDa Resolving Power ~4,500,000 15N 1347 1348 1349 1350 1351 1352 m/z 1348.728 33S 1348.736 17O 2H 1348.742 m/z Resolving power and complex samples Edge Article 244,779 assignments (world record) Chem. Sci., 2019, 10, pp. 6966-6978 Non-distillable fraction of petroleum Fig. 6 Red line: mass resolving power calc Resolving power and complex samples Theoretical broadband resolving o er eri ental resolving o er 0.45 mDa 0.56 mDa 0. mDa. mDa. mDa 244,779 assignments (world record) Chem. Sci., 2019, 10, pp. 6966-6978 Next lecture: Ionization
