Development of a Novel Mass Spectrometric ... - Jacobs University

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Results and Discussion Intens. [%] 325.4 C22 +MS 80 60 40 20 0 C24 C18 C20 353.4 269.3 297.3 339.3 375.4 240 260 280 300 320 340 360 380 400 m/z Figure 3-8 APCI mass spectrum of n-paraffin mixture Overall the mass spectrum is considerably simpler than that provided by EI or CI. The production of intact abundant stable n-alkane ions that are representative for their n-alkane precursor neutral analytes is the utmost achievement in my study. For many years, mass spectrometry was considered incapable to analyse alkane species. By this careful ionisation study of n-alkanes, the analyses of the latters are no more out of reach. This novel approach enabled to extend the applicability of reactive APCI-MS towards n-alkanes. The next step was to apply this unique methodology to other types of hydrocarbons whether separate or model mixtures. The method was successfully applied to a wider range of n-alkanes such as for C12-C60 n-alkane standard mixture as illustrated in Figure 3-9. Intens. [%] 100 617.7 701.8 +MS 80 60 505.6 561.6 663.4 40 20 0 242.9 219.2 449.5 338.3 421.5 283.3 309.3 365.4 393.4 523.6 543.6 599.6 647.5 487.5 579.6 633.7 717.8 739.8 841.9 200 300 400 500 600 700 800 m/z Figure 3-9 APCI mass spectrum of C12-C60 alkane standard 43
Results and Discussion 3.2 APCI-TOF-MS of a Variety of Hydrocarbons Encouraged by the success in controlling the ionisation process of n-alkanes upon APCI, we have attempted to examine a wide variety of hydrocarbons. To probe the APCI capability, different standards of non-polar hydrocarbons were investigated under positive APCI-TOF-MS conditions. The compounds were chosen due to previous literature reports stating that ionization using APCI in the absence of an additive failed to produce molecular or pseudomolecular ions. Therefore these compounds must be considered a benchmark for difficult analytes. The ionisation of a whole set of model standards including various non-polar hydrocarbons was studied. Model compounds were divided into three groups as considering solvent requirements and molecular weight distributions. The first group involved the eight Chiron standards which were diluted in isooctane before injection. Phytane, n- decyl benzene and 5-α-cholestane were prepared in n-heptane and were also injected together as a second model mixture. The last group consisted of the remaining high molecular weight (MW) alkanes which were prepared in n-heptane prior to infusion. All analytes in the three groups were easily evaporated by APCI heating chamber which reached up to 450 ˚C. Figure 3-11 shows the spectrum of the eight Chiron hydrocarbon mixture. All analytes in the mixture are in equal molar ratios. Initial inspection of the spectrum shows that each analyte was impressively ionized and detected as intact stable [M- H] + ion with minor or no fragmentation as obvious in Figure 3-11. This ion was shown to be accompanied by another radical molecular cation M •+ . The intensity of this molecular ion appears to be directly related to the intensity of the major ion, [M-H] + , regardless of the structure of the studied compounds. Figure 3-11 also demonstrates that the relative abundances measured for the [M-H] + ions of these compounds are close to each other except for n-octadecyl benzene (10). Despite the fact that those eight analytes are different in terms of volatility, structure and composition, their product ions have close relative abundances that match their relative molar concentrations. N-decyl benzene, phytane and 5-α-cholestane were measured together. 44
Page 1 and 2:
Development of a Novel Mass Spectro
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Declaration of Authorship I ,Nadim
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This work has been carried out unde
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Contents Contents Declaration of Au
Page 9 and 10: List of Figures List of Figures Fig
Page 11 and 12: List of Figures Figure 3-39 MS 2 fr
Page 13 and 14: List of Tables List of Tables Table
Page 15 and 16: Abbreviations Abbreviations APCI AP
Page 17 and 18: Abbreviations UV VGOs VOCs VRs ultr
Page 19 and 20: Introduction Analytical chemistry h
Page 21 and 22: Introduction 1.2 Presence and Fate
Page 23 and 24: Introduction aliphatic hydrocarbons
Page 25 and 26: Introduction Figure 1-1 Examples of
Page 27 and 28: Introduction Figure 1-2 Range of io
Page 29 and 30: Introduction fractions. 42 Another
Page 31 and 32: Introduction 1.3.5 APLI Other crude
Page 33 and 34: Introduction products). Other molec
Page 35 and 36: Introduction Other studies performe
Page 37 and 38: Introduction APLI-FT ICR-MS Crude o
Page 39 and 40: Introduction spectrometry in as muc
Page 41 and 42: Introduction catalytic processing t
Page 43 and 44: Introduction Figure 1-6 Kendrick ma
Page 45 and 46: Introduction including determinatio
Page 47 and 48: Introduction 1.5 Scope and Signific
Page 49 and 50: Experimental e) Other model mixture
Page 51 and 52: Experimental 2.2.2 Preparation of O
Page 53 and 54: Experimental 2.4 Graphical Presenta
Page 55 and 56: Results and Discussion experiment.
Page 57 and 58: Results and Discussion Intens. [%]
Page 59: Results and Discussion common featu
Page 63 and 64: Results and Discussion These compou
Page 67 and 68: Results and Discussion Ions were pr
Page 71 and 72: Results and Discussion procedure ba
Page 75 and 76: Results and Discussion to produce m
Page 77 and 78: Results and Discussion 519.5863 519
Page 79 and 80: Results and Discussion Higher mass
Page 87 and 88: Results and Discussion isolated fro
Page 93 and 94: Results and Discussion 3.4.5 Tandem
Page 97 and 98: Results and Discussion injected int
Page 101 and 102: Results and Discussion 3.4.8 Quanti
Page 103 and 104: Results and Discussion Int. x 10000
Page 105 and 106: Results and Discussion Table 3.6 Qu
Page 107 and 108: Results and Discussion assessment o
Page 109 and 110: Results and Discussion hydrocarbons
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Results and Discussion Intens. [%]
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Results and Discussion of n-alkanes
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Results and Discussion flow (in I2)
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Results and Discussion Other intere
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Results and Discussion Figure 3-80
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Results and Discussion KMD 2.4 2.2
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Results and Discussion KMD 1.1 1 Le
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Results and Discussion 3.6.4 Asphal
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Conclusions In conclusion we could
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References References 1. Fay, R. M.
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References 23. Colavecchia, M. V.,
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References 47. Dzidic, I., Petersen
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References Hydroconversion Processe
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References 91. Golovlev, V. V., All
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Appendix Light shredder waste Meas.
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419.4592 C 30 H 59 419.4611 4.6 421
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Liqui Moly car motor oil Meas. m/z
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345.3511 C 25 H 45 345.3516 1.5 349
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