CEE 772: Instrumental Methods in Environmental Analysis Lecture #19 - PDF document

CEE 772 Lecture #17 11/11/2014 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 1

CEE 772 Lecture #17 11/11/2014 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 12 Response 5.0e+4 4.0e+4 11 4 67 13 3 3.0e+4 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 2

CEE 772 Lecture #17 11/11/2014 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 4 67 11 13 3.0e+4 3 10 12 15 14 16 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 Response 3.0e+4 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 3

CEE 772 Lecture #17 11/11/2014 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 4

CEE 772 Lecture #17 11/11/2014 Basics of an MS instrument • Major components Inlet Ion Mass Data Detector System Source Analyzer System Vacuum Pumps • Vacuum: 10 ‐ 4 to 10 ‐ 8 torr David Reckhow CEE 772 #19 9 Mass Spectra • Ethyl Benzene David Reckhow CEE 772 #19 10 5

CEE 772 Lecture #17 11/11/2014 Fragmentation • 1 ‐ decanol – A. Hard Source – B. Soft Source David Reckhow CEE 772 #19 11 Interfaces • Jet Separator David Reckhow CEE 772 #19 12 6

CEE 772 Lecture #17 11/11/2014 Ion Source • Electron Impact David Reckhow CEE 772 #19 13 Interface & Ion Source • Electrospray Ionization David Reckhow CEE 772 #19 14 7

CEE 772 Lecture #17 11/11/2014 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 8

CEE 772 Lecture #17 11/11/2014 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 9

CEE 772 Lecture #17 11/11/2014 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 10

CEE 772 Lecture #17 11/11/2014 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 11

CEE 772 Lecture #17 11/11/2014 From: McLafferty, 1980 David Reckhow CEE 772 #18 23 From: McLafferty, 1980 David Reckhow CEE 772 #18 24 12

CEE 772 Lecture #17 11/11/2014 David Reckhow CEE 772 #18 25 From: McLafferty, 1980 From: McLafferty, 1980 David Reckhow CEE 772 #18 26 13

CEE 772 Lecture #17 11/11/2014 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 14

CEE 772 Lecture #17 11/11/2014 From: Skoog, 1985 David Reckhow CEE 772 #18 29 From: Skoog, 1985 David Reckhow CEE 772 #18 30 15

CEE 772 Lecture #17 11/11/2014 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 16

CEE 772 Lecture #17 11/11/2014 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 17

CEE 772 Lecture #17 11/11/2014 David Reckhow CEE 772 #19 35 From: McLafferty, 1980 From: McLafferty, 1980 David Reckhow CEE 772 #19 36 18

CEE 772 Lecture #17 11/11/2014 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 19

CEE 772 Lecture #17 11/11/2014 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 20

CEE 772 Lecture #17 11/11/2014 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 21