1. http://lawrencekok.blogspot.com Prepared by Lawrence Kok Tutorial on Mass Spectrometer and Isotopes

2. Atomic Structure and Isotopes Isotopes – Atoms of same element with Different number of neutrons Same number of proton Same number of electrons Due to presence of isotopes, when calculating RAM, the weighted average/mean of all isotopes present will have to used. X - No isotopes RAM/Ar X Mass of 1 atom X Mass of 1/12 of 12 C Mass of 1 atom X relative to 1/12 mass of 1 atom 12 C Relative Abundance 75% 25% Mass number = proton + neutron Proton number = protonZ = 29 protons A= 29 protons + 35 neutrons = 64 Isotopes Y - TWO isotopes RAM/Ar Y Average Mass of 1 atom Y Mass of 1/12 of 12 C Average mass of 1 atom Y relative to 1/12 mass of 1 atom 12 C RAM for CI Weighted average mass of 2 isotopes present = (mass 53 CI x % Abundance) + (mass 37 CI x % Abundance) = (35 x 75/100) + (37 x 25/100) = 35.5 CI - TWO isotopes

3. Mg has 3 Isotopes Relative Abundance Pb has 4 Isotopes Relative Abundance

4. Mg has 3 Isotopes 24 Mg – (100/127.2) x 100% - 78.6% 25 Mg – (12.8/127.2) x 100% - 10.0% 26 Mg – (14.4/127.2) x 100% - 11.3% Relative Abundance% Abundance Pb has 4 Isotopes 204 Pb – (0.2/10) x 100% - 2% 206 Pb – (2.4/10) x 100% - 24% 207 Pb – (2.2/10) x 100% - 22% 208 Pb – (5.2/10) x 100% - 52% Convert relative abundance to % abundance Relative Abundance% Abundance

5. Mg has 3 Isotopes 24 Mg – (100/127.2) x 100% - 78.6% 25 Mg – (12.8/127.2) x 100% - 10.0% 26 Mg – (14.4/127.2) x 100% - 11.3% RAM for Mg : = (Mass 24 Mg x % Abundance) + (Mass 25 Mg x % Abundance) + (Mass 26 Mg x % Abundance) = (24 x 78.6/100) + (25 x 10.0/100) + (26 x 11.3/100) = 24.30 Relative Abundance% Abundance Pb has 4 Isotopes 204 Pb – (0.2/10) x 100% - 2% 206 Pb – (2.4/10) x 100% - 24% 207 Pb – (2.2/10) x 100% - 22% 208 Pb – (5.2/10) x 100% - 52% RAM for Pb : = (Mass 204 Pb x % Abundance) + (Mass 206 Pb x % Abundance) + (Mass 207 Pb x % Abundance) + (Mass 208 Pb x % Abundance) = (204 x 2/100) + (206 x 24/100) + (207 x 22/100) + (208 x 52/100) = 207.20 Convert relative abundance to % abundance Relative Abundance% Abundance

6. Mass spectrophotometer Separates particles according to their masses and record their relative abundance Use to determine presence of isotopes and its abundance Use to calculate relative atomic mass /relative molecular mass of substance Use to determine structural of organic molecules Use to distinguish between structural isomers Mass Spectrometer Parts of Mass Spectrometer Sample injection Vaporization Chamber Sample heat to vapour state Ionization Chamber Molecule bombard with electrons form positive ions Accelerator Chamber M + ions accelerated by Electric field Deflector M+ ions deflected by magnetic field Detector Measure m/z ratio Relative abundance of ions http://www.mhhe.com/physsci/chemistry/carey/student/olc/ch13ms.html Sample X bombarded by electron Form positive M+ ion Accelerated (Electric Field) Deflected (Magnetic Field) and Detected X + e- → X + + 2e-

7. Ionization and Fragmentation Process Ionization Process - CH 3 CH 2 CH 2 CH 3 Bombarded by electron forming cation Molecular ion, M + = 58 (CH 3 CH 2 CH 2 CH 3 ) + = 58 Fragmentation Process CH 3 CH 2 CH 2 CH 3 Molecular ion, M+ undergo fragmentation Cation and Radical formed Cation will be detected Radical - Not charged –Not detected Ionization, M +,m/z = 58 Ionization and Fragmentation of M + Forming - m/z = 58, 43 and 15 Ionization and Fragmentation of M + Forming- m/z = 58 and 29

8. Ionization forming M + CH 3 CH 2 CH 2 : CH 3 + e → CH 3 CH 2 CH 2 +.CH 3 + 2e Fragmentation of M + producing 43 CH 3 CH 2 CH 2 + ·CH 3 → CH 3 CH 2 CH 2 + + ·CH 3 Fragmentation of M + producing 15 CH 3 CH 2 CH 2 + ·CH 3 → CH 3 CH 2 CH 2 · + + CH 3 Ionization and Fragmentation Process Ionization Process - CH 3 CH 2 CH 2 CH 3 Bombarded by electron forming cation Molecular ion, M + = 58 (CH 3 CH 2 CH 2 CH 3 ) + = 58 Fragmentation Process CH 3 CH 2 CH 2 CH 3 Molecular ion, M+ undergo fragmentation Cation and Radical formed Cation will be detected Radical - Not charged –Not detected H H | | CH 3 CH 2 CH 2 C:H + e → CH 3 CH 2 CH 2 C +.H + 2e | | H H Ionization forming M + CH 3 CH 2 :CH 2 CH 3 + e → CH 3 CH 2 + ·CH 2 CH 3 + 2e Fragmentation of M + producing 29 CH 3 CH 2 + ·CH 2 CH 3 → CH 3 CH 2 + +. CH 2 CH 3 Ionization, M +,m/z = 58 CH 3 CH 2 CH 2 CH 3 + e → CH 3 CH 2 CH 2 CH 3 + + 2e Ionization and Fragmentation of M + Forming - m/z = 58, 43 and 15 m/z = 58 m/z = 43 m/z = 15 Ionization and Fragmentation of M + Forming- m/z = 58 and 29 m/z = 58 m/z = 29

9. Ionization forming M + CH 3 CH 2 CH 2 : CH 3 + e → CH 3 CH 2 CH 2 +.CH 3 + 2e Fragmentation of M + producing 43 CH 3 CH 2 CH 2 + ·CH 3 → CH 3 CH 2 CH 2 + + ·CH 3 Fragmentation of M + producing 15 CH 3 CH 2 CH 2 + ·CH 3 → CH 3 CH 2 CH 2 · + + CH 3 Ionization and Fragmentation Process Ionization Process - CH 3 CH 2 CH 2 CH 3 Bombarded by electron forming cation Molecular ion, M + = 58 (CH 3 CH 2 CH 2 CH 3 ) + = 58 Fragmentation Process CH 3 CH 2 CH 2 CH 3 Molecular ion, M+ undergo fragmentation Cation and Radical formed Cation will be detected Radical - Not charged –Not detected H H | | CH 3 CH 2 CH 2 C:H + e → CH 3 CH 2 CH 2 C +.H + 2e | | H H Ionization forming M + CH 3 CH 2 :CH 2 CH 3 + e → CH 3 CH 2 + ·CH 2 CH 3 + 2e Fragmentation of M + producing 29 CH 3 CH 2 + ·CH 2 CH 3 → CH 3 CH 2 + +. CH 2 CH 3 Ionization, M +,m/z = 58 CH 3 CH 2 CH 2 CH 3 + e → CH 3 CH 2 CH 2 CH 3 + + 2e Ionization and Fragmentation of M + Forming - m/z = 58, 43 and 15 m/z = 58 m/z = 43 m/z = 15 Ionization and Fragmentation of M + Forming- m/z = 58 and 29 m/z = 58 m/z = 29 Ionization and Fragmentation

10. Ionization of CI 2 into CI 2 + CI:CI + e- → CI +.CI + 2e [ 35 CI +. 35 CI] – 70 CI:CI + e- → CI +.CI + 2e [ 35 CI +. 37 CI] – 72 CI:CI + e- → CI +.CI + 2e [ 37 CI +. 37 CI] – 74 Fragmentation of CI 2 + into CI + CI +.CI → CI + + ·CI [ 35 CI + + 35 CI·] – 35 CI +.CI → CI + + ·CI [ 37 CI + + 37 CI·] – 37 m/z = 35 m/z = 37 Ionization and Fragmentation Process CI 2 molecule (Isotopes) undergo Ionization and Fragmentation

11. Fragmentation of CI 2 + into CI + CI +.CI → CI + + ·CI [ 35 CI + + 35 CI·] – 35 CI +.CI → CI + + ·CI [ 37 CI + + 37 CI·] – 37 m/z = 35 m/z = 37 Ionization and Fragmentation Process Mass spectrum for CI 2 molecule CI 2 molecule (Isotopes) undergo Ionization and Fragmentation Ratio for 35 CI 35 CI: 35 CI 37 CI: 37 CI 37 CI is 9:6:1 Ratio for 35 CI : 37 CI is 3:1 Ionization of CI 2 into CI 2 + CI:CI + e- → CI +.CI + 2e [ 35 CI +. 35 CI] – 70 CI:CI + e- → CI +.CI + 2e [ 35 CI +. 37 CI] – 72 CI:CI + e- → CI +.CI + 2e [ 37 CI +. 37 CI] – 74

12. Deflection based on mass/charge ratio or (m/z) ratio Ion – LOW ↓ mass (light) + HIGH ↑ charge – Deflected ↑ more (LOW ↓ (m/z) ratio ) Ion – HIGH ↑ mass ( heavy) + LOW ↓ charge – Deflect ↓ less (HIGH ↑ (m/z) ratio ) Click here to viewhere LOW ↓ (m/z) ratio – HIGH ↑ Deflection HIGH ↑ (m/z) ratio - LOW ↓ Deflection Fragmentation of CI 2 + into CI + CI +.CI → CI + + ·CI [ 35 CI + + 35 CI·] – 35 CI +.CI → CI + + ·CI [ 37 CI + + 37 CI·] – 37 37 CI + 35 CI + 35 CI 2+ 37 CI 2+ m/z = 35 m/z = 37 Ionization and Fragmentation Process Mass spectrum for CI 2 molecule CI 2 molecule (Isotopes) undergo Ionization and Fragmentation Ratio for 35 CI 35 CI: 35 CI 37 CI: 37 CI 37 CI is 9:6:1 Ratio for 35 CI : 37 CI is 3:1 Ionization of CI 2 into CI 2 + CI:CI + e- → CI +.CI + 2e [ 35 CI +. 35 CI] – 70 CI:CI + e- → CI +.CI + 2e [ 35 CI +. 37 CI] – 72 CI:CI + e- → CI +.CI + 2e [ 37 CI +. 37 CI] – 74

13. http://www.mhhe.com/physsci/chemistry/carey/student/olc/ch13ms.html#isotopes Mass spectra for CH 3 (CH 2 ) 8 CH 3 Mass spectra for C 6 H 5 CH 2 OH Molecular Ion peak, M + = [C 6 H 5 CH 2 OH] + = 108 Fragmentation peaks : (M- 17) + = (C 6 H 5 CH 2 ) + = 91 (M- 31) + = (C 6 H 5 ) + = 77 (M- 77) + = (CH 2 OH) + = 31 Molecular Ion peak, M + = [CH 3 (CH 2 ) 8 CH 3 ] + = 142 Fragmentation peaks : (M-15) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 127 (M-29) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 113 (M-43) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 99 (M-57) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 85 (M-71) + =(CH 3 CH 2 CH 2 CH 2 CH 2 ) + = 71 (M-85) + =(CH 3 CH 2 CH 2 CH 2 ) + = 57 (M-99) + = (CH 3 CH 2 CH 2 ) + = 43 (M-113) + = (CH 3 CH 2 ) + = 29 (M-127) + = (CH 3 ) + = 15 Loss of Methylene gp, CH 2 = 14 Loss of CH 2 OH Loss of OH Loss of C 6 H 5

14. http://www.mhhe.com/physsci/chemistry/carey/student/olc/ch13ms.html#isotopes Mass spectra for CH 3 (CH 2 ) 8 CH 3 127 Mass spectra for C 6 H 5 CH 2 OH Molecular Ion peak, M + = [C 6 H 5 CH 2 OH] + = 108 Fragmentation peaks : (M- 17) + = (C 6 H 5 CH 2 ) + = 91 (M- 31) + = (C 6 H 5 ) + = 77 (M- 77) + = (CH 2 OH) + = 31 Molecular Ion peak, M + = [CH 3 (CH 2 ) 8 CH 3 ] + = 142 Fragmentation peaks : (M-15) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 127 (M-29) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 113 (M-43) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 99 (M-57) + =(CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 ) + = 85 (M-71) + =(CH 3 CH 2 CH 2 CH 2 CH 2 ) + = 71 (M-85) + =(CH 3 CH 2 CH 2 CH 2 ) + = 57 (M-99) + = (CH 3 CH 2 CH 2 ) + = 43 (M-113) + = (CH 3 CH 2 ) + = 29 (M-127) + = (CH 3 ) + = 15 Loss of Methylene gp, CH 2 = 14 Loss of CH 2 OH Loss of OH Loss of C 6 H 5

15. http://www.mhhe.com/physsci/chemistry/carey/student/olc/ch13ms.html#isotopes Mass spectra for CH 3 CH(CI)CH 3 Molecular Ion peak, M + = [CH 3 CH( 35 CI)CH 3 ] + = 78 ( 35 CI) Molecular Ion peak, M + = [CH 3 CH( 37 CI)CH 3 ] + = 80 ( 37 CI) Fragmentation peaks : (M-15) + =(CH 3 CH 35 CI) + = 63 (M-15) + =(CH 3 CH 37 CI) + = 65 (M-35/37) + =(CH 3 CHCH 3 ) + = 43 Loss of methyl gp CH 3 Loss of CI gp Mass spectra for CH 3 CH 2 CH 3 Br Molecular Ion peak, M + = [CH 3 CH 2 CH 2 Br] + = 122 ( 79 Br) Molecular Ion peak, M + = [CH 3 CH 2 CH 2 Br] + = 124 ( 81 Br) Fragmentation peaks : (M-79/81) + =(CH 3 CH 2 CH 2 ) + = 43 (M- 29) + =(CH 2 79 Br) + = 93 (M- 29) + =(CH 2 81 Br) + = 95 Loss of Br gp Loss of ethyl gp CH 3 CH 2

16. http://www.mhhe.com/physsci/chemistry/carey/student/olc/ch13ms.html#isotopes Isotopic peak – (M + + 2) peak present due to 35 CI and 37 CI Mass spectra for CH 3 CH(CI)CH 3 Molecular Ion peak, M + = [CH 3 CH( 35 CI)CH 3 ] + = 78 ( 35 CI) Molecular Ion peak, M + = [CH 3 CH( 37 CI)CH 3 ] + = 80 ( 37 CI) Fragmentation peaks : (M-15) + =(CH 3 CH 35 CI) + = 63 (M-15) + =(CH 3 CH 37 CI) + = 65 (M-35/37) + =(CH 3 CHCH 3 ) + = 43 Loss of methyl gp CH 3 Loss of CI gp Mass spectra for CH 3 CH 2 CH 3 Br Molecular Ion peak, M + = [CH 3 CH 2 CH 2 Br] + = 122 ( 79 Br) Molecular Ion peak, M + = [CH 3 CH 2 CH 2 Br] + = 124 ( 81 Br) Fragmentation peaks : (M-79/81) + =(CH 3 CH 2 CH 2 ) + = 43 (M- 29) + =(CH 2 79 Br) + = 93 (M- 29) + =(CH 2 81 Br) + = 95 Isotopic peak – (M + + 2) peak present due to 79 Br and 81 Br Loss of Br gp Loss of ethyl gp CH 3 CH 2 9395

17. Mass Spectrum for Isomers, 2 methylbutane and 2, 2 dimethylpropane CH 3 | CH 3 CHCH 2 CH 3 CH 3 | CH 3 C-CH 3 | CH 3 Isomers of C 5 H 12 Vs 2 methylbutane 2, 2 dimethylpropane

18. Mass Spectrum for Isomers, 2 methylbutane and 2, 2 dimethylpropane CH 3 | CH 3 CHCH 2 CH 3 CH 3 | CH 3 C-CH 3 | CH 3 Molecular Ion, M + = [CH 3 CH(CH 3 )CH 2 CH 3 ] + = 72 Fragmentation peaks : (M - 15) + = (CH 3 CH(CH 3 )CH 2 ) + = 57 (M - 29) + = (CH 3 CH(CH 3 )) + = 43 (M - 43) + = (CH 3 CH 2 ) + = 29 (M - 57) + = (CH 3 ) + = 15 Isomers of C 5 H 12 Molecular Ion, M + = [CH 3 CH(CH 3 )CH 2 CH 3 ] + = 72 Fragmentation peaks : (M - 15) + = (C(CH 3 ) 3 ) + = 57 (M - 30) + = (C(CH 3 ) 2 ) + = 42 (M - 45) + = (CH 3 C) + = 27 (M - 57) + = (CH 3 ) + = 15 Vs Loss of CH 3 Loss of CH 3 CH 2 Loss of CH 3 CH(CH 3 ) Loss of CH 3 CH(CH 3 )CH 2 Loss of CH 3 Loss of T WO CH 3 Loss of THREE CH 3 2 methylbutane 2, 2 dimethylpropane Loss of C(CH 3 ) 3 Vs

19. Mass Spectrum for Isomers, 2 methylbutane and 2, 2 dimethylpropane CH 3 | CH 3 CHCH 2 CH 3 CH 3 | CH 3 C-CH 3 | CH 3 Peak 29 absent No CH 3 CH 2 present Peak 57 is higher Loss of methyl radical produces a tertiary carbocation Tertiary carbocation – More stable Molecular Ion, M + = [CH 3 CH(CH 3 )CH 2 CH 3 ] + = 72 Fragmentation peaks : (M - 15) + = (CH 3 CH(CH 3 )CH 2 ) + = 57 (M - 29) + = (CH 3 CH(CH 3 )) + = 43 (M - 43) + = (CH 3 CH 2 ) + = 29 (M - 57) + = (CH 3 ) + = 15 Isomers of C 5 H 12 Molecular Ion, M + = [CH 3 CH(CH 3 )CH 2 CH 3 ] + = 72 Fragmentation peaks : (M - 15) + = (C(CH 3 ) 3 ) + = 57 (M - 30) + = (C(CH 3 ) 2 ) + = 42 (M - 45) + = (CH 3 C) + = 27 (M - 57) + = (CH 3 ) + = 15 Vs Loss of CH 3 Loss of CH 3 CH 2 Loss of CH 3 CH(CH 3 ) Loss of CH 3 CH(CH 3 )CH 2 Loss of CH 3 Loss of T WO CH 3 Loss of THREE CH 3 CH 3 | CH 3 C + ·CH 3 | CH 3 m/z= 57 CH 3 | CH 3 C + + ·CH 3 | CH 3 2 methylbutane 2, 2 dimethylpropane Loss of C(CH 3 ) 3 Vs Peak 29 absent CH 3 CH 2 present

20. Mass Spectrum for Isomers, Propan-1-ol and Propan-2-ol Isomers of C 3 H 8 OH CH 3 CH 2 CH 2 OH OH | CH 3 CHCH 3 Propan-1-ol Propan-2-ol

21. Mass Spectrum for Isomers, Propan-1-ol and Propan-2-ol Molecular Ion, M + = [CH 3 CH 2 CH 2 OH] + = 60 Fragmentation peaks : (M - 15) + = (CH 2 CH 2 OH) + = 45 (M - 29) + = (CH 2 OH) + = 31 (M - 31) + = (CH 3 CH 2 ) + = 29 (M - 45) + = (CH 3 ) + = 15 Isomers of C 3 H 8 OH Molecular Ion, M + = [CH 3 CH(OH)CH 3 ] + = 60 Fragmentation peaks : (M - 15) + = (CH 3 CH(OH)) + = 45 (M - 17) + = (CH 3 CHCH 3 ) + = 43 (M - 33) + = (CH 3 C) + = 27 Vs Loss of CH 3 Loss of CH 3 CH 2 Loss of CH 2 OH Loss of CH 2 CH 2 OH Loss of CH 3 CH 3 CH 2 CH 2 OH OH | CH 3 CHCH 3 Loss of OH Loss of OH, CH 3, H Propan-1-ol Propan-2-ol 15 Vs

22. Mass Spectrum for Isomers, Propan-1-ol and Propan-2-ol Peak 45 is higher Loss of methyl radical at both sides produces (CH 3 CH(OH)) + No m/z= 29 peak detected – No CH 2 CH 3 found ! Molecular Ion, M + = [CH 3 CH 2 CH 2 OH] + = 60 Fragmentation peaks : (M - 15) + = (CH 2 CH 2 OH) + = 45 (M - 29) + = (CH 2 OH) + = 31 (M - 31) + = (CH 3 CH 2 ) + = 29 (M - 45) + = (CH 3 ) + = 15 Isomers of C 3 H 8 OH Molecular Ion, M + = [CH 3 CH(OH)CH 3 ] + = 60 Fragmentation peaks : (M - 15) + = (CH 3 CH(OH)) + = 45 (M - 17) + = (CH 3 CHCH 3 ) + = 43 (M - 33) + = (CH 3 C) + = 27 Vs Loss of CH 3 Loss of CH 3 CH 2 Loss of CH 2 OH Loss of CH 2 CH 2 OH Loss of CH 3 OH OH | | CH 3 C + ·CH 3 → CH 3 C + + ·CH 3 | | H H m/z= 45 CH 3 CH 2 CH 2 OH OH | CH 3 CHCH 3 Loss of OH Loss of OH, CH 3, H Peak 29 and 31 are found Inductive effect of OH causes splitting of CH 3 CH 2 -|-CH 2 OH m/z =29 peak detected – CH 2 CH 3 present CH 3 CH 2 + · CH 2 OH → CH 3 CH 2 + + ·CH 2 OH m/z= 29 CH 3 CH 2 + · CH 2 OH → CH 3 CH 2 · + + CH 2 OH m/z= 31 Propan-1-ol Propan-2-ol 15 Vs

23. Normal Mass Spectrometer Vs High Resolution Mass spectrometer Normal Mass Spectrometer Determination molecular formula/weight by adding all relative atomic mass RMM for molecule = Sum of all RAM RMM for O 2 = 16 + 16 = 32 RMM for N 2 H 4 = (14 x 2) + (1 x 4) =32 RMM for CH 3 OH = (12 + 3 + 16 + 1) = 32 Molecular ion peak, for O 2, N 2 H 4, CH 3 OH is the SAME = 32 RAM, O = 16 RAM, N = 14 RAM, H = 1 RAM, C = 12 High Resolution Mass Spectrometer - Measure to RMM to 4/5 decimal places Determination molecular formula/weight by adding all relative atomic mass RMM for molecule = Sum of all RAM RMM for O 2 = 15.9949 + 15.9949 = 31.9898 RMM for N 2 H 4 = (14.0031 x 2) + (1.0078 x 4) = 32.0375 RMM for CH 3 OH = (12.0000 )+ (3 x 1.0078) + 15.9949 = 32.0262 Molecular ion peak, for O 2, N 2 H 4, CH 3 OH is the NOT the same RAM, O = 15.9949 RAM, N = 14.0031 RAM, H = 1.0078 RAM, C = 12.0000 Vs

24. Normal Mass Spectrometer Vs High Resolution Mass spectrometer Normal Mass Spectrometer Determination molecular formula/weight by adding all relative atomic mass RMM for molecule = Sum of all RAM RMM for O 2 = 16 + 16 = 32 RMM for N 2 H 4 = (14 x 2) + (1 x 4) =32 RMM for CH 3 OH = (12 + 3 + 16 + 1) = 32 Molecular ion peak, for O 2, N 2 H 4, CH 3 OH is the SAME = 32 RAM, O = 16 RAM, N = 14 RAM, H = 1 RAM, C = 12 High Resolution Mass Spectrometer - Measure to RMM to 4/5 decimal places Determination molecular formula/weight by adding all relative atomic mass RMM for molecule = Sum of all RAM RMM for O 2 = 15.9949 + 15.9949 = 31.9898 RMM for N 2 H 4 = (14.0031 x 2) + (1.0078 x 4) = 32.0375 RMM for CH 3 OH = (12.0000 )+ (3 x 1.0078) + 15.9949 = 32.0262 Molecular ion peak, for O 2, N 2 H 4, CH 3 OH is the NOT the same RAM, O = 15.9949 RAM, N = 14.0031 RAM, H = 1.0078 RAM, C = 12.0000 Vs

25. Normal Mass Spectrometer Vs High Resolution Mass spectrometer Normal Mass Spectrometer Determination molecular formula/weight by adding all relative atomic mass RMM for molecule = Sum of all RAM RMM for O 2 = 16 + 16 = 32 RMM for N 2 H 4 = (14 x 2) + (1 x 4) =32 RMM for CH 3 OH = (12 + 3 + 16 + 1) = 32 Molecular ion peak, for O 2, N 2 H 4, CH 3 OH is the SAME = 32 RAM, O = 16 RAM, N = 14 RAM, H = 1 RAM, C = 12 High Resolution Mass Spectrometer - Measure to RMM to 4/5 decimal places Determination molecular formula/weight by adding all relative atomic mass RMM for molecule = Sum of all RAM RMM for O 2 = 15.9949 + 15.9949 = 31.9898 RMM for N 2 H 4 = (14.0031 x 2) + (1.0078 x 4) = 32.0375 RMM for CH 3 OH = (12.0000 )+ (3 x 1.0078) + 15.9949 = 32.0262 Molecular ion peak, for O 2, N 2 H 4, CH 3 OH is the NOT the same RAM, O = 15.9949 RAM, N = 14.0031 RAM, H = 1.0078 RAM, C = 12.0000 (M+1 )– due to isotope 13 C as Carbon has 3 isotopes, 12, 13 and 14 Naturally occuring carbon made up of 98.9% 12 C and 1.1% 13 C Relative abundance for M+1 ( 13 C) peak is very small 59 Vs CH 3 CH 2 CH 2 CH 3 Molecular ion peak/parent ion – Highest m/z value = RMM of compound Molecular ion, M + = 58 (CH 3 CH 2 CH 2 CH 3 ) + = 58 Mass spectrum for CH 3 CH 2 CH 2 CH 3 Vs

26. Acknowledgements Thanks to source of pictures and video used in this presentation Thanks to Creative Commons for excellent contribution on licenses http://creativecommons.org/licenses/ Prepared by Lawrence Kok Check out more video tutorials from my site and hope you enjoy this tutorial http://lawrencekok.blogspot.com