Christoph Zuth, Alexander L. Vogel, Sara Ockenfeld, Regina Huesmann and Thorsten Hoffmann * S-1. Supporting Information for:

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1 Supporting Information for: Ultra-High-Resolution Mass Spectrometry in Real-Time: Atmospheric Pressure Chemical Ionization Orbitrap Mass Spectrometry (APCI- Orbitrap-MS) of Atmospheric Organic Aerosol Christoph Zuth, Alexander L. Vogel, Sara Ockenfeld, Regina Huesmann and Thorsten Hoffmann * Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University, Mainz, 55128, Germany Laboratory for Environmental Chemistry & Laboratory for Atmospheric Chemistry, Paul Scherrer Institute, Villigen, 5232, Switzerland now at: Institute for Atmospheric and Environmental Sciences, Goethe University, Frankfurt, 60438, Germany * Corresponding Author t.hoffmann@uni-mainz.de This file contains the supporting figures S-1 to S-13 and supporting tables S-1 to S-9. Figure S-1. Scheme of the instrumental setup for the measurement of ambient aerosol particles. Figure S-2. Venn Diagrams of the detected molecular formulas in negative ionization mode (a) and positive ionization mode (b) for nightand daytime 1. S-1

2 Figure S-3. Pie Charts of the detected molecular formulas classes in negative ionization mode at night (a) and day (b) and positive ionization mode at night (c) and day (d). The colors correspond to the CHO (green), CHON (blue), CHOS (red), CHONS (cyan), CH (magenta) and CHN (yellow) formulas assignments. Figure S-4. Temporal variation during the measurement period. (upper panel) PM 2.5 Particle Size distribution measured with an SMPS. The color keys relate to the number size distribution (log10(dn/dlogdp)/cm-3). (central panel) Aerosol mass concentration. (lower panel) Time traces of the deprotonated signals of C10H15N1O7 (m/z , [M-H] - ) and C15H23N1O8 (m/z , [M-H] - ). S-2

3 Figure S-5. Temperature and relative humidity profiles on August 15 th, The sudden drop in the temperature and increase of the relative humidity at 14:00 was caused by a heavy rain event in Mainz, Germany. (Source: Institute for Atmospheric Physics, Johannes Gutenberg University Mainz, Mainz). Figure S-6. Number of compound distribution of the CHO-containing formulas (left axis) and intensity-weighted contribution of the corresponding O-containing subclass to the measured particulate organic aerosol (right axis) in the negative ionization mode at nighttime (a) and daytime (b). S-3

4 Figure S-7. Number of compound distribution of the CHON-containing formulas (left axis) and intensity-weighted contribution of the corresponding O-containing subclass to the measured particulate organic aerosol (right axis) in the negative ionization mode at nighttime (a) and daytime (b). The contribution of organic nitrates is calculated to 14 % at night and 5 % at day. Figure S-8. Ambient MS²-spectrum of m/z (± 0.4) (HCD energy 10 %). The fragmentation pattern indicates the presence of an organic peroxy nitrate (C15H23O10N): m/z ([M-H] - ), m/z ([M- 2H2O2] - ), m/z ([C15H18O6N-C7H9O5N] - ), m/z ([M-C15H18O3] - ). S-4

5 Figure S-9. Simulated mass spectra of C15H23O11N2 - (blue) and C21H27O8 - (green) at the Orbitrap resolving power of R = (bold lines), R = (dashed lines) and R = (dotted lines) illustrate the mass spectra of both compounds at a mass resolving power of R = Figure S-10. APCI-Orbitrap mass spectrum of oxidation products formed in the reaction of α-pinene with ozone in the negative ionization mode. The spectra shows a monomer and a dimer-mode of main oxidation products. The detected particle phase was separated from the gasphase prior to the ionization by use of a charcoal denuder system. α-pinene was purchased from Sigma-Aldrich ( purity > 99%). The experiment was performed in a cylindrical reaction chamber made of glass with a volume of 85 L at a temperature of 296 ± 2 K. The α-pinene mixing ratio was 140 ppb. Ozone was produced by UV irradiation of a synthetic air supply and measured with a Dasibi Environmental Corp. O3 analyser (model 1008-RS, Glendale, CA, USA). The O3 concentration was adjusted to a range of 1 ppm. S-5

6 Figure S-11. Mass spectra of the reaction of α-pinene with ozone obtained in the negative ionization mode by an Orbitrap-MS (red, R~ 70 m/z 400) and a ToF-CIMS (blue, R~ 4 m/z 400). The spectra shows an insight of the dimer-mode at the nominal mass of m/z 357. The Orbitrap-MS spectra clearly shows the signals hidden under a ToF-MS spectra. Figure S-12. a) Ambient MS² spectrum of m/z 203 (± 0.4 Th) recorded with APCI-Orbitrap-MS. b) MS² spectrum of synthesized laboratory standard MBTCA recorded with UHPLC-Orbitrap-MS at a retention time of 3.05 min. The fragmentation pattern strongly indicates the presence of MBTCA in the ambient particle phase: m/z ([M-H] - ), m/z ([M-H2O] - ), m/z ([M-CO2] - ), m/z ([M-H2O-CO2] - ), m/z ([M-2 CO2] - ), m/z ([M-H2O-2 CO2] - ). Additional signals may originate from isobaric interferences. S-6

7 Figure S-13. Calibration plots for different particle sizes (i.e., a) 40 nm, b) 70 nm, c) 100 nm) selected by a DMA. The different particle sizes were analyzed using differing APCI set point temperatures: 400 C (blue), 350 C (red), 300 C (orange), and 250 C (green). The linear regression shows rather identical calibration slopes for 40 nm particles with varying APCI set point temperatures. For 70 nm and 100 nm particles, the lower APCI set point temperatures show lower calibration slopes indicating possibly incomplete vaporization/ionization at temperatures below 350 C. S-7

8 The non-target screening distinguished 931 and 247 monoisotopic formulas above a signal-threshold of cts in negative and positive mode, respectively. The intensity value was chosen by evaluating certain intensities of already described dimeric SOA products (e.g. C 19H 27O 7, ([M-H] - ), C 17H 25O 8 ([M-H] - ))². The intensities of prominent SOA markers were checked for certain threshold settings after blank correction. The Molecular formulas for the identified signals were calculated using a mass tolerance of ±2 ppm and the following constraints: #C (1 45), #H (1 60), #O (0 20), #N (0 4), #S (0 2). Additionally, the abundance and intensity of the 13C isotopic peak were checked by XCalibur 2.2 (Thermo Scientific). Neutral formulas with chemically impossible compositions, e.g., non-integer or negative double bond equivalents (DBE) and unreasonable O/C and H/C element ratios (O/C < 3; 0.3 < H/C < 3) were discarded. Table S-1. CHO containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in negative ionization mode. measured m/z ([M-H] - ) elemental composition H/C O/C DBE C3H4O C3H6O C4H4O C3H2O C4H6O C3H4O C4H8O C3H6O C5H4O C4H2O C5H6O C4H4O C5H8O C4H6O C5H10O C4H8O C8H8O C7H6O C8H10O C6H4O C7H8O C8H12O C6H6O C7H10O C8H14O C5H4O C6H8O C7H12O C8H16O S-8

9 C5H6O C6H10O C7H14O C4H4O C5H8O C9H8O C6H12O C4H6O C8H6O C5H10O C9H10O C7H4O C4H8O C8H8O C9H12O C7H6O C8H10O C9H14O C6H4O C7H8O C8H12O C9H16O C6H6O C7H10O C8H14O C9H18O C5H4O C6H8O C10H8O C7H12O C8H16O C5H6O C9H6O C6H10O C10H10O C7H14O C8H4O C5H8O C9H8O C6H12O C10H12O C4H6O C8H6O S-9

10 C5H10O C9H10O C10H14O C7H4O C8H8O C9H12O C10H16O C7H6O C8H10O C9H14O C10H18O C6H4O C7H8O C8H12O C9H16O C10H20O C6H6O C7H10O C11H10O C8H14O C9H18O C6H8O C10H8O C7H12O C8H16O C5H6O C9H6O C6H10O C10H10O C7H14O C11H14O C8H4O C5H8O C9H8O C6H12O C10H12O C11H16O C8H6O C5H10O C9H10O C10H14O C11H18O C7H4O S-10

11 C4H8O C8H8O C9H12O C10H16O C11H20O C7H6O C8H10O C12H10O C9H14O C10H18O C11H22O C7H8O C11H8O C8H12O C9H16O C10H20O C6H6O C10H6O C7H10O C11H10O C8H14O C9H18O C6H8O C10H8O C7H12O C11H12O C8H16O C12H16O C9H6O C6H10O C10H10O C11H14O C12H18O C8H4O C9H8O C6H12O C10H12O C11H16O C12H20O C8H6O C9H10O C10H14O C11H18O S-11

12 C12H22O C8H8O C9H12O C10H16O C11H20O C12H24O C7H6O C8H10O C12H10O C9H14O C10H18O C11H22O C7H8O C11H8O C8H12O C12H12O C9H16O C10H20O C6H6O C10H6O C7H10O C11H10O C8H14O C12H14O C9H18O C9H4O C6H8O C10H8O C7H12O C11H12O C12H16O C9H6O C6H10O C10H10O C11H14O C12H18O C9H8O C10H12O C11H16O C12H20O C8H6O C9H10O C13H10O S-12

13 C10H14O C11H18O C12H22O C13H26O C8H8O C12H8O C9H12O C10H16O C11H20O C12H24O C11H6O C8H10O C12H10O C9H14O C13H14O C10H18O C11H22O C12H26O C7H8O C11H8O C8H12O C12H12O C9H16O C13H16O C10H20O C10H6O C7H10O C11H10O C8H14O C12H14O C9H18O C13H18O C14H22O C10H8O C7H12O C11H12O C12H16O C13H20O C9H6O C10H10O C11H14O C12H18O C13H22O S-13

14 C9H8O C13H8O C10H12O C14H12O C11H16O C12H20O C13H24O C14H28O C12H6O C9H10O C13H10O C10H14O C11H18O C12H22O C13H26O C8H8O C12H8O C9H12O C13H12O C10H16O C11H20O C12H24O C11H6O C8H10O C12H10O C9H14O C13H14O C10H18O C14H18O C11H22O C7H8O C11H8O C8H12O C12H12O C9H16O C13H16O C10H20O C14H20O C15H24O C11H10O C8H14O C12H14O C13H18O S-14

15 C14H22O C14H8O C11H12O C15H12O C12H16O C13H20O C14H24O C10H10O C14H10O C11H14O C15H14O C12H18O C13H22O C14H26O C15H30O C9H8O C13H8O C10H12O C14H12O C11H16O C12H20O C13H24O C14H28O C9H10O C13H10O C10H14O C14H14O C11H18O C12H22O C16H22O C13H26O C8H8O C12H8O C9H12O C13H12O C10H16O C14H16O C11H20O C15H20O C12H24O C16H24O C8H10O C12H10O S-15

16 C9H14O C13H14O C10H18O C14H18O C15H22O C11H8O C8H12O C12H12O C13H16O C14H20O C15H24O C11H10O C12H14O C13H18O C10H22O C14H22O C15H26O C14H8O C15H12O C12H16O C13H20O C14H24O C15H28O C10H10O C14H10O C7H14O C11H14O C15H14O C12H18O C13H22O C14H26O C15H30O C10H12O C14H12O C11H16O C15H16O C12H20O C13H24O C14H28O C9H10O C13H10O C10H14O C14H14O S-16

17 C11H18O C15H18O C12H22O C16H22O C9H12O C13H12O C10H16O C14H16O C11H20O C15H20O C16H24O C12H10O C9H14O C13H14O C14H18O C15H22O C16H26O C12H12O C13H16O C14H20O C15H24O C16H28O C12H14O C16H14O C13H18O C14H22O C15H26O C16H30O C11H12O C15H12O C12H16O C16H16O C13H20O C14H24O C15H28O C16H32O C10H10O C11H14O C15H14O C12H18O C16H18O C13H22O C14H26O S-17

18 C15H30O C10H12O C14H12O C11H16O C15H16O C12H20O C16H20O C13H24O C17H24O C10H14O C14H14O C11H18O C15H18O C12H22O C16H22O C17H26O C13H12O C10H16O C14H16O C15H20O C16H24O C17H28O C13H14O C14H18O C15H22O C16H26O C17H30O C12H12O C16H12O C13H16O C17H16O C14H20O C15H24O C16H28O C17H32O C12H14O C16H14O C13H18O C14H22O C15H26O C16H30O C17H34O C11H12O S-18

19 C12H16O C16H16O C13H20O C14H24O C15H28O C16H32O C11H14O C15H14O C12H18O C16H18O C13H22O C14H26O C18H26O C10H12O C11H16O C15H16O C12H20O C16H20O C17H24O C18H28O C14H14O C15H18O C16H22O C17H26O C18H30O C14H16O C15H20O C16H24O C17H28O C18H32O C13H14O C14H18O C15H22O C12H26O C16H26O C17H30O C18H34O C16H12O C13H16O C17H16O C14H20O C15H24O C16H28O S-19

20 C17H32O C18H36O C12H14O C16H14O C13H18O C17H18O C14H22O C15H26O C16H30O C11H12O C12H16O C16H16O C13H20O C17H20O C14H24O C15H28O C16H32O C11H14O C12H18O C16H18O C13H22O C18H26O C16H20O C17H24O C18H28O C15H18O C16H22O C17H26O C18H30O C19H34O C14H16O C18H16O C15H20O C16H24O C17H28O C18H32O C19H36O C14H18O C18H18O C15H22O C16H26O C20H26O C17H30O S-20

21 C18H34O C19H38O C13H16O C17H16O C14H20O C15H24O C16H28O C20H28O C17H32O C18H36O C12H14O C13H18O C17H18O C14H22O C15H26O C16H30O C20H30O C17H34O C12H16O C13H20O C17H20O C14H24O C20H32O C18H26O C20H34O C16H20O C17H24O C18H28O C19H32O C20H36O C15H18O C16H22O C17H26O C21H26O C18H30O C19H34O C20H38O C14H16O C18H16O C15H20O C19H20O C16H24O C17H28O S-21

22 C21H28O C18H32O C19H36O C20H40O C14H18O C18H18O C15H22O C16H26O C20H26O C17H30O C21H30O C18H34O C13H16O C14H20O C15H24O C16H28O C20H28O C18H36O C13H18O C14H22O C20H30O C18H26O C19H30O C20H34O C21H38O C16H20O C17H24O C18H28O C19H32O C20H36O C15H18O C16H22O C17H26O C14H30O C18H30O C19H34O C20H38O C21H42O C15H20O C16H24O C17H28O C18H32O C19H36O S-22

23 C14H18O C15H22O C16H26O C18H34O C14H20O C15H24O C20H28O C20H30O C21H34O C19H28O C20H32O C21H36O C18H26O C19H30O C20H34O C21H38O C22H42O C17H24O C18H28O C19H32O C20H36O C22H44O C16H22O C17H26O C18H30O C15H20O C16H24O C20H24O C18H32O C15H22O C20H30O C21H34O C19H28O C21H36O C23H44O C18H26O C19H30O C21H38O C23H46O C17H24O C18H28O C16H22O C17H26O S-23

24 C21H34O C24H46O C19H28O C21H36O C24H48O C18H26O C21H34O C24H46O C21H36O C26H52O C28H56O Table S-2. CHON containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in negative ionization mode. measured m/z ([M-H] - ) elemental composition H/C O/C DBE C4H5N1O C4H7N1O C3H5N1O C4H9N1O C2H4N2O C2H3N1O C5H5N1O C4H3N1O C4H5N1O C3H3N1O C4H7N1O C3H6N2O C3H5N1O C4H9N1O C6H7N1O C5H5N1O C4H4N2O C4H3N1O C5H7N1O C3H2N2O C4H6N2O C4H5N1O C5H9N1O C3H4N2O C4H7N1O C7H5N1O C7H7N1O C6H5N1O S-24

25 C5H3N1O C5H6N2O C6H9N1O C4H4N2O C5H8N2O C4H3N1O C5H7N1O C6H11N1O C4H5N1O C5H9N1O C7H5N1O C8H9N1O C7H7N1O C6H6N2O C6H5N1O C7H9N1O C5H4N2O C5H3N1O C6H7N1O C7H11N1O C5H6N2O C5H5N1O C6H9N1O C7H13N1O C5H7N1O C6H11N1O C8H5N1O C5H9N1O C7H4N2O C8H7N1O C7H5N1O C8H9N1O C7H8N2O C7H7N1O C8H11N1O C6H6N2O C6H5N1O C7H9N1O C8H13N1O C5H4N2O C5H3N1O C6H7N1O C7H11N1O S-25

26 C5H5N1O C6H9N1O C5H7N1O C9H7N1O C8H6N2O C8H5N1O C9H9N1O C7H3N1O C8H7N1O C9H11N1O C7H6N2O C7H5N1O C8H9N1O C7H8N2O C7H7N1O C8H11N1O C6H5N1O C7H9N1O C8H13N1O C9H4N2O C6H8N2O C6H7N1O C7H11N1O C6H9N1O C9H7N1O C9H10N2O C8H5N1O C9H9N1O C7H3N1O C8H7N1O C9H11N1O C7H5N1O C8H9N1O C9H13N1O C6H4N2O C7H7N1O C8H11N1O C7H9N1O C8H13N1O C9H17N1O C10H7N1O C7H11N1O C9H5N1O S-26

27 C10H9N1O C9H7N1O C10H11N1O C10H13N1O C8H7N1O C9H11N1O C7H6N2O C8H9N1O C9H13N1O C8H11N1O C11H9N1O C8H13N1O C10H7N1O C10H10N2O C9H5N1O C10H9N1O C9H7N1O C6H11N1O C10H11N1O C11H15N1O C9H9N1O C10H13N1O C8H7N1O C9H11N1O C10H15N1O C11H19N1O C12H10N2O C8H11N1O C10H7N1O C7H11N1O C10H9N1O C11H13N1O C10H11N1O C11H18N2O C9H9N1O C10H13N1O C11H17N1O C9H11N1O C10H15N1O C9H13N1O C7H11N1O C10H9N1O C11H13N1O S-27

28 C12H20N2O C10H11N1O C10H13N1O C10H15N1O C8H11N1O C8H13N1O C14H21N1O C10H13N1O C10H15N1O C9H13N1O C10H17N1O C9H15N1O C15H23N1O C14H21N1O C10H13N1O C12H24N2O C10H15N1O C16H23N1O C9H13N1O C10H17N1O C16H25N1O C10H15N1O C12H17N1O C16H33N1O C12H19N1O C18H29N1O C12H17N1O C13H21N1O C12H19N1O C18H33N1O C8H11N1O C15H23N1O C15H25N1O C18H37N1O C15H23N1O C15H25N1O C16H19N3O C15H23N1O C18H35N1O C15H25N1O C11H17N1O C15H23N1O C19H29N1O S-28

29 C20H9N1O C15H24N2O Table S-3. CHONS containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in negative ionization mode. measured m/z ([M-H] - ) elemental composition H/C O/C DBE C7H5N1O1S C6H7N1O2S C7H9N1O2S C10H13N1O2S C10H15N1O2S C7H15N1O3S C10H19N3O1S C10H17N1O7S C9H13N1O7S C8H11N1O10S C19H25N1O1S C10H15N1O7S C9H13N1O10S C16H13N1O5S C15H19N3O4S C11H17N1O7S C10H15N1O10S C10H17N1O10S C12H19N1O7S C11H17N1O10S C9H13N1O10S C8H11N1O13S C13H21N1O7S C12H19N1O10S C11H19N1O11S C17H15N3O5S C19H7N1O6S C14H23N1O7S C13H21N1O10S S-29

30 C10H15N3O12S C23H33N1O3S C21H11N1O6S C20H43N3O1S S-30

31 Table S-4. CHOS containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in negative ionization mode. measured m/z ([M-H] - ) elemental composition H/C O/C DBE C2H2O4S C3H6O5S C9H4O2S C7H12O6S C6H10O7S C8H16O6S C16H26O1S C17H26O1S C11H18O12S C10H16O13S C10H10O14S Table S-5. CHO containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in positive ionization mode. measured m/z ([M+H] + ) elemental composition H/C O/C DBE C3H6O C5H6O C7H4O C8H8O C7H6O C8H10O C6H4O C7H8O C6H6O C7H10O C6H8O C7H12O C8H16O C7H14O C8H18O C9H8O C6H12O C7H16O C8H6O C9H10O C8H8O C9H12O C7H6O C8H10O S-3 1

32 C9H14O C7H8O C8H12O C9H16O C7H10O C8H14O C9H18O C6H8O C7H12O C8H16O C9H6O C10H10O C7H14O C8H4O C5H8O C9H8O C6H12O C10H12O C8H6O C9H10O C10H14O C8H8O C9H12O C10H16O C8H10O C9H14O C10H18O C7H8O C8H12O C9H16O C10H20O C7H10O C8H14O C9H18O C10H8O C7H12O C11H12O C8H16O C9H6O C10H10O C7H14O C11H14O C8H18O S-3 2

33 C9H8O C10H12O C11H16O C5H10O C9H10O C10H14O C11H18O C8H8O C9H12O C10H16O C11H20O C8H10O C9H14O C10H18O C11H22O C8H12O C9H16O C10H20O C11H10O C12H14O C10H8O C11H12O C8H16O C12H16O C10H10O C11H14O C12H18O C10H12O C11H16O C12H20O C9H10O C13H10O C10H14O C11H18O C12H22O C9H12O C10H16O C11H20O C12H24O C9H14O C10H18O C11H22O C12H14O S-33

34 C13H18O C12H16O C13H20O C11H14O C12H18O C10H12O C11H16O C12H20O C13H24O C10H14O C11H18O C12H22O C13H26O C10H16O C12H24O C14H18O C14H20O C14H22O C12H16O C13H20O C14H24O C14H10O C12H18O C13H22O C14H26O C12H20O C13H24O C14H28O C13H26O C10H16O C15H20O C15H22O C14H20O C15H24O C13H18O C14H22O C15H26O C7H12O C13H20O C14H24O C15H28O C13H22O C14H26O S-34

35 C15H30O C14H28O C16H24O C15H22O C15H24O C16H28O C17H18O C15H26O C16H30O C15H28O C16H32O C15H30O C16H34O C13H24O C16H22O C16H24O C16H26O C14H20O C15H24O C16H28O C17H32O C16H30O C17H34O C16H32O C17H24O C16H24O C18H34O C17H32O C18H36O C17H34O C17H22O C17H24O C16H22O C19H36O C18H34O C19H38O C18H36O C10H16O C20H40O C21H42O C22H44O C23H46O C24H48O S-35

36 C22H42O C12H20O C24H38O C26H42O C15H24O Table S-6. CHON containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in positive ionization mode. measured m/z ([M+H] + ) elemental composition H/C O/C DBE C10H15N1O C10H21N1O C11H12N4O C12H15N3O C14H21N1O C15H11N3O C16H20N4O C17H14N4O C21H13N3O C4H9N1O C5H11N1O C5H6N2O C6H13N1O C6H5N1O C7H7N1O C7H8N4O C8H10N4O C8H5N1O C9H18N2O C9H19N1O Table S-7. CH containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in positive ionization mode. measured m/z ([M+H] + ) elemental composition H/C O/C DBE C11H C11H C11H C11H C12H C12H C12H C12H C13H S-36

37 C13H C14H C15H C15H C16H Table S-8. CHOS containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in positive ionization mode. measured m/z ([M+H] + ) elemental composition H/C O/C DBE C8H14O5S C12H18O10S C13H22O10S Table S-9. CHN containing molecular formulas during 09 May 12 May 2017 determined by APCI-Orbitrap-MS in positive ionization mode. measured m/z ([M+H] + ) elemental composition H/C O/C DBE C5H6N C7H9N C6H8N C10H14N C12H11N C13H21N C14H21N C16H35N REFERENCES (1) Oliveros, J.C. ( ) Venny. An interactive tool for comparing lists with Venn`s diagrams. (2) Müller, L.; Reinnig, M.-C.; Hayen, H.; Hoffmann, T. Rapid Commun. Mass Spectrom. 2009, DOI: /rcm S-37