CH3F2 Mass Spectrometry Handout (2023-2024) PDF

CH3F2 (Advanced Analytical Chemistry) Mass Spectrometry: Data Dr. Mark P. Barrow Sample preparation Sample preparation: MALDI “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-3-319-54397-0 Sample preparation: MALDI “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-...

CH3F2 (Advanced Analytical Chemistry) Mass Spectrometry: Data Dr. Mark P. Barrow Sample preparation Sample preparation: MALDI “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-3-319-54397-0 Sample preparation: MALDI “Mass Spectrometry: A textbook,” Jürgen Gross, Springer, ISBN: 978-3-319-54397-0 Sample preparation: ESI and APPI Concentration of liquid samples for ESI and APPI: o Can be ~0.1 µM for single compounds o Can be ~0.05 mg/mL for mixtures o Do not use same sample solutions for mass spectrometry and NMR (NMR samples may be ~10,000x more concentrated) Choose appropriate solvents: o Solubility of analyte o Volatility of solvent o Good proton carrier/donor for ESI or dopant for APPI When using internal standards (quantitation or calibration), often desirable to use isotopically labelled compounds Sample preparation Analyte response typically decreases with increases in the concentration of additives or contaminants (e.g. detergents) “Ion suppression” Competition with analyte for charge and occupation on the droplet surface Can use liquid-liquid extraction (LLE) or solid-phase extraction (SPE) during sample preparation (clean up) Solid-phase extraction Contamination https://doi.org/10.1016/j.aca.2008.04.043 Contamination https://beta-static.fishersci.ca/content/dam/fishersci/en_US/documents/programs/scientific/brochures-and-catalogs/posters/fisher-chemical-poster.pdf Data acquisition and analysis Calibration Mass spectrometers and mass spectra require calibration o Needed to ensure experimental m/z readings are accurate o TOF: temperature changes o FTMS (Orbitrap and FTICR): “space-charge” effects (Coulombic repulsion between ions when trapped) Create a reference list of compounds expected to appear (e.g. dope sample with a standard) Match relevant peak in mass spectrum with theoretical m/z in reference list Software calculates calibration fit Calibration Linear calibration o y = ax + c (or y = mx + c) o Good for wide m/z ranges o Less problematic if analyte lies outside range of calibrant values (although still undesirable) Quadratic calibration o y = ax2 + bx + c o ESI TOF instruments often use quadratic or higher order polynomial functions o Critical that analyte is “bracketed” within m/z range of calibrant peaks Data analysis When assigning compositions to peaks in mass spectra, typically consider the following: o Elemental constraints (e.g. minimum/maximum number of each of C, H, N, O, S) o Adducts (M+H, M+Na, etc.) o Even or odd electron species (e.g. [M+H]+ or M+ ) o Double bond equivalents (DBE) (rings and double bonds) o Charge o Mass error Isotope pattern Common fragment ions "Mass Spectrometry," James McCullagh and Neil Oldham, Oxford Chemistry Primers, ISBN: 9780198789048 Common neutral losses "Mass Spectrometry," James McCullagh and Neil Oldham, Oxford Chemistry Primers, ISBN: 9780198789048 “Seven Golden Rules” Rule 1: Restrictions for element numbers Rule 2: LEWIS and SENIOR check Rule 3: Isotopic pattern filter Rule 4: Hydrogen/carbon element ratio check Rule 5: Heteroatom ratio check Rule 6: Element probability check Rule 7: TMS check T. Kind, O. Fiehn, BMC Bioinformatics, 2007, 8, 105, DOI: 10.1186/1471-2105-8-105 Advanced data analysis Double bond equivalents (DBE) “Double bond equivalents” (DBE) or “Rings plus double bond equivalents” (RDBE) = C + Si - 1/2(H+F+Cl+Br+I) + 1/2(N+P) + 1 Simplifying, for an organic molecule CcHhNnOoSs DBE = 1 + c – h/2 + n/2 Based on valence of elements. Note oxygen and sulfur do not contribute to equations when valence of 2 is assumed. C6H6 (benzene) Neutral Protonated species Radical ion Formula: C6 H6 [C6H6 + H]+ C6H6+ DBE: 4.0 3.5 4.0 Integer values for odd electron species (radical ions) Half integer values for even electron species (protonated/deprotonated) Double bond equivalents (DBE) Formula: DBE: C3H8O3S2 C3H8O3S2 0 0 DBE used as a measure for rings and double bonds involving carbon http://fiehnlab.ucdavis.edu/projects/Seven_Golden_Rules/Ring-Double-Bonds Complex samples Crude oil ~20,000 peaks Complex samples 14.01565 Da CH2 2.01565 Da H2 ~m/z 385 - 414 Patterns throughout data (H2 and CH2) Complex samples ~m/z 400.00 - 400.40 Kendrick mass defect (KMD) Based upon work of Kendrick in 1963 (Anal. Chem., 1963, 35, pp. 2146-2154) Principle is to normalize mass scale to CH2 instead of 12C Kendrick mass and Kendrick mass defect are given by: Kendrick mass defect (KMD) Example: C23H43O2 IUPAC mass: 351.32685 (Exact) Kendrick mass = 351.32685 x (14.00000/14.01565) = 350.93456 Nominal Kendrick mass = 351 Kendrick mass defect = 351 - 350.93456 = 0.06544 Monoisotopic masses: C: 12.000000 H: 1.007825 O: 15.994915 Electron: 0.000548 Kendrick mass defect (KMD) Increasing the DBE changes the KMD KMD: 0.00055 KMD: 0.04075 Alkyl chains do not change the KMD KMD: 0.00055 KMD: 0.04075 Kendrick mass defect (KMD) KMD: 0.00055 KMD: 0.04075 Adding heteroatoms changes the KMD KMD: 0.02349 KMD: 0.06369 Visualization Kendrick mass defect (KMD) Increasing rings and double bonds (DBE) Patterns significantly simplify/speed up data analysis Adding CH2 (Homologous series) CcH(2c+Z)Oo where o = 2-5 in this case and Z is “hydrogen deficiency” (negative, even integer) F WARWICK on August 21, 2019 at 13:42:20 (UTC). elines for options on how to legitimately share published articles. Other uses of KMD Article Cite This: Anal. Chem. 2018, 90, 11710−11715 pubs.acs.org/ac Coupling Electron Capture Dissociation and the Modified Kendrick Mass Defect for Sequencing of a Poly(2-ethyl-2-oxazoline) Polymer Tomos E. Morgan,† Sean H. Ellacott,† Christopher A. Wootton,† Mark P. Barrow,† Anthony W. T. Bristow,‡ Sebastien Perrier,† and Peter B. O’Connor*,† † Department of Chemistry, University of Warwick, Coventry, Midlands CV4 7AL, U.K. AstraZeneca, Macclesfield, Cheshire SK10 2NA, U.K. ‡ S Supporting Information * ABSTRACT: With increasing focus on the structural elucidation of polymers, advanced tandem mass spectrometry techniques will play a crucial role in the characterization of these compounds. In this contribution, synthesis and analysis of methyl-initiated and xanthate-terminated poly(2-ethyl-2oxazoline) using Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) was achieved. Electron capture dissociation (ECD) produced full end group characterization as well as backbone fragmentation including complete sequence coverage of the polymer. A method of fragment ion characterization is also presented with the use of the high-resolution-modified Kendrick mass defect plots as a means of grouping fragments from the same fragmentation pathways together. This type of data processing is applicable to all tandem mass spectrometry techniques for polymer analysis but is made more effective with high mass accuracy methods. ECD FT-ICR MS demonstrates its promising role as a structural characterization technique for polyoxazoline species. olyoxazolines have recently gained interest as an than that of other methods, such as collision-induced/activated Anal. Chem., 2018, 90, pp. 11710-11715 Can normalize to compositions other than CH2, use of a modified KMD DBE vs. carbon number [CcHhN1 + H]+ Adding rings and double bonds Anal. Chem., 2014, 86, pp. 527-534 Adding CH2 DBE vs. carbon number Annual Review of Analytical Chemistry, 2020, 13, 1, pp. 405-430 van Krevelen diagram Complex samples Natural organic matter (NOM) Dissolved organic matter (DOM) Environ. Sci. Technol., 2018, 52, 2091−2099 CRAM: “Carboxylic-rich alicyclic molecules” van Krevelen diagram Annual Review of Analytical Chemistry, 2020, 13, 1, pp. 405-430 CH3F2: Mass spectrometry Principles of mass spectrometry (Dr. Mark Barrow) § Basics § Ionization § Analyzers § Tandem mass spectrometry § Data Applications of mass spectrometry (Prof. Peter O’Connor) CH3F2: Mass spectrometry CH3F2: Mass spectrometry