Updated: 11 November 2014 Print version CEE 772: Instrumental Methods in Environmental Analysis Lecture #19 Mass Spectrometry: Basics (Skoog, Chapt. 11, 26, 27, 28, pp.253-271, 674-693 718-721, 738-739 ) (Harris, Chapt. 23, 24 & 25) (641-664, 699-706; 742-749) David Reckhow CEE 772 #19 1
Calibration 300 250 Standard Curve 200 Peak Area Sample Peak Area 150 100 Estimated Sample Concentration 50 0 0 5 10 15 20 25 30 Concentration (µg/L) David Reckhow CEE 772 #19 2
Example Number Name Retention Time (min) 1 2-Methylhexane 2.83 2 2,2,4-Trimethylpentane 3.12 3 3-Methylheptane 4.74 4 Ethylbenzen 6.69 5 m-Xylene 6.86 6 o-Xylene 7.38 7 Nonane 7.54 8 Cumene 8.07 9 1,2,4-Trimethylbenzene 9.48 10 Decane 9.59 11 Undecane 11.42 12 Naphthalene 12.96 13 1-Methylnaphthalene 15.00 14 Tetradecane 16.12 15 2,3-Dimethylnaphthalene 16.85 16 Pentadecane 17.48 David Reckhow CEE 772 #19 3
3.0e+4 Response Solvent Blank 2.0e+4 1.0e+4 0.0e+0 5 16-Compound Standard Solvent 8.0e+4 9 7.0e+4 6.0e+4 Response 12 5.0e+4 4.0e+4 11 4 67 13 3.0e+4 3 15 10 12 16 14 2.0e+4 8 1.0e+4 0.0e+0 0 2 4 6 8 10 12 14 16 18 Retention Time (min) David Reckhow CEE 772 #19 4
9.0e+4 16-Compound Standard Solvent 5 8.0e+4 9 7.0e+4 6.0e+4 12 Response 5.0e+4 4.0e+4 11 4 67 13 3.0e+4 3 15 10 12 16 14 2.0e+4 8 1.0e+4 0.0e+0 Floating Product 6.0e+4 5.0e+4 Response 4.0e+4 3.0e+4 2.0e+4 1.0e+4 0.0e+0 0 2 4 6 8 10 12 14 16 18 Retention Time (min) David Reckhow CEE 772 #19 5
6.0e+4 Floating Product 5.0e+4 4.0e+4 Response 3.0e+4 2.0e+4 1.0e+4 0.0e+0 Soil Extract 4.0e+4 3.0e+4 Response 2.0e+4 1.0e+4 0.0e+0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Retention Time (min) David Reckhow CEE 772 #19 6
Mass Spectrometry • General References on Instrument Design – Skoog, Principles of Instrumental Analysis • 1985 (3 rd ed): parts of Chapter 18 • 1991 (4 th ed): parts of Chapter 18 • 1998 (5 th ed): parts of Chapter 20 – Howe, Williams & Bowen, Mass Spectrometry, Principles & Applications • 1981 (2 nd ed): Chapter 1 & 12 – Loconto, Trace Environmental Quantitative Analysis • 2001: pp356-370 – Budde, Analytical Mass Spectrometry • 2001: parts of Chapter 1 & 2 David Reckhow CEE 772 #19 7
Use of MS with Chromatography • Provides a 3 rd dimension to chromatograms with molecular weight info • GC/MS – Used in environ- Packed column GC mental field for 20 (76 cm), isothermal using 20% years Carbowax; From: Harris, 2000 • LC/MS – Newer David Reckhow CEE 772 #19 8
Basics of an MS instrument • Major components In le t Io n M a ss D a ta D e te c to r S yste m S o u rc e A n a lyze r S yste m V acuum P um ps • Vacuum: 10 -4 to 10 -8 torr David Reckhow CEE 772 #19 9
Mass Spectra • Ethyl Benzene David Reckhow CEE 772 #19 10
Fragmentation • 1-decanol – A. Hard Source – B. Soft Source David Reckhow CEE 772 #19 11
Interfaces • Jet Separator David Reckhow CEE 772 #19 12
Ion Source • Electron Impact David Reckhow CEE 772 #19 13
Interface & Ion Source • Electrospray Ionization David Reckhow CEE 772 #19 14
Mass Spectral Interpretation • References – McLafferty, 1980; Interpretation of Mass Spectra, 3 rd Ed., – University Science Books, Mill Valley, CA David Reckhow CEE 772 #19 15
Mass Spec • Typical reactions in electron impact David Reckhow CEE 772 #19 16
Mass Spec • Electron Impact – Methylene Chloride – 1- Pentanol David Reckhow CEE 772 #19 17
Mass Spec • Glutamic Acid – Electron impact • Harsh, more fragments – Field Ionization • intermediate – Field Desorption • Very mild, mostly molecular ion David Reckhow CEE 772 #19 18
Isotopic Abundances • Elemental Signatures From: McLafferty, 1980 David Reckhow CEE 772 #19 19
Number of Carbon atoms From: McLafferty, 1980 David Reckhow CEE 772 #19 20
Abundance Chart • Isotopic Abundances for combinations of “A+2” elements David Reckhow CEE 772 #19 21 From: McLafferty, 1980
From: McLafferty, 1980 David Reckhow CEE 772 #18 22
From: McLafferty, 1980 David Reckhow CEE 772 #18 23
From: McLafferty, 1980 David Reckhow CEE 772 #18 24
David Reckhow CEE 772 #18 25 From: McLafferty, 1980
From: McLafferty, 1980 David Reckhow CEE 772 #18 26
Mass Spectral Interpretation • References – Fred McLafferty, Interpretation of Mass Spectra • University Science Books, Mill Valley, CA – 3 rd Ed., 1980 – 4 th Ed., 1993 (with František Ture č ek) – McLafferty & Venkataraghavan, 1982; Mass Spectral Correlations, 2 nd Ed., – American Chemical Society, Advances in Chemistry Series #40 David Reckhow CEE 772 #18 27
From: Skoog, 1985 David Reckhow CEE 772 #18 28
From: Skoog, 1985 David Reckhow CEE 772 #18 29
From: Skoog, 1985 David Reckhow CEE 772 #18 30
Chemical Ionization • Use of reagent gas at high pressures (0.2-2 torr) – Methane – Ammonia • Ionize reagent gas • These ions react with and ionize analyte – Pseudo-M ions • M-1, M, M+1 – Adduct ions • M+17, 29, 57 David Reckhow CEE 772 #18 31
CI: proton transfer • Proton transfer will occur from conjugate bases of substances of lower affinity to those higher From: Budde, 2001 David Reckhow CEE 772 #18 32
CI Spectra • Spectra of di- Methane CI isooctylphthalate Isobutane CI From: Howe et al., 1981, Mass Spectrometry, Principles and Applications David Reckhow CEE 772 #18 33
Mass Spectral Interpretation • References – Fred McLafferty, Interpretation of Mass Spectra • University Science Books, Mill Valley, CA – 3 rd Ed., 1980 – 4 th Ed., 1993 (with František Ture č ek) – McLafferty & Venkataraghavan, 1982; Mass Spectral Correlations, 2 nd Ed., – American Chemical Society, Advances in Chemistry Series #40 David Reckhow CEE 772 #19 34
David Reckhow CEE 772 #19 35 From: McLafferty, 1980
From: McLafferty, 1980 David Reckhow CEE 772 #19 36
Mass Spectrometry • General References on Instrument Design – Skoog, Principles of Instrumental Analysis • 1985 (3 rd ed): parts of Chapter 18 • 1991 (4 th ed): parts of Chapter 18 • 1998 (5 th ed): parts of Chapter 20 – Howe, Williams & Bowen, Mass Spectrometry, Principles & Applications • 1981 (2 nd ed): Chapter 1 & 12 – Loconto, Trace Environmental Quantitative Analysis • 2001: pp356-370 – Budde, Analytical Mass Spectrometry • 2001, Oxford University Press, – parts of Chapter 1 & 2 David Reckhow CEE 772 #19 37
Mass Spectrometry • MS – molecules are ionized and separated based on the their mass to charge ratio (m/z) • The molecules are bombarded by electrons and the molecules release 1 or more electrons • M + e - _ > M + + 2e - David Reckhow CEE 772 #19 38
MS Schematic Figure 18-1, Skoog David Reckhow CEE 772 #19 39
MS Inlet System • Introduce the sample to the MS • 3 types – batch inlet – direct probe inlet – chromatographic inlet David Reckhow CEE 772 #19 40
References • Hardy, James, http://ull.chemistry.uakron.edu/gcms/index.html, 2001 • Harris, Daniel, Quantitative Chemical Analysis,W.H. Freeman and Company, New York, 1999 McLafferty, F.W., Interpretation of Mass Spectra, University Science Books, • Mill Valley, CA, 1980 • Schoenberg, Ted, “The Hewlett Packard HP5890A GC/ HP5988A MS System,” 1997 • Skoog, Douglas; Leary, James; Principles of Instrumental Analysis, Saunders College Publishing, New York, 1992 • HP 5988A Mass Spectrometer System Hardware and Service Manual, 1985 David Reckhow CEE 772 #19 41
• To next lecture David Reckhow CEE 772 #19 42
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