Mass spectrometry (1)

Mass spectrometer Power point Presentation

1. Mass Spectrometry Presented By: Mohsin Shad 2013-BC-005 Jahanzaib azhar 2013-BC-017 Asmat Shahzad 2013-BC-026 Muhammad Zulqarnain 2013-BC-027 Hamza Zafar 2013-BC-032 Presented To: Dr.Muhammad tayyab 1

2. Mass Spectrometry Technique involves : - Creating gas phase ions from the analyte atoms or molecules - Separating the ions according to their mass-to-charge ratio (m/z) - Measuring the abundance of the ions - Qualitative and quantitative analysis - Providing information about the mass of atoms and molecules - Molecular structure determination (organic & inorganic - Identification and characterization of materials 2

3. PRINCIPLE of Mass Spectrometry Mass spectra is also called positive ion spectra. In this electron bombardment is used to convert a neutral molecule in to positively charged one. Obtaining mass spectra consists 2 steps Conversion of neutral molecule in to positively charge done. Separation of positively charged fragments formed based upon their masses using electrical & magnetic field: 3

4. PRINCIPLE of Mass Spectrometry Separates gas phase ionized atoms, molecules, and fragments of molecules Separation is based on the difference in mass-to-charge ratio (m/z) m = unified atomic mass units (u) 1 dalton (Da) = 1 u = 1.665402 x 10-27 kg z = charge on the ion (may be positive or negative 4

5. PRINCIPLE of Mass Spectrometry  Analyte molecule can undergo electron ionization M + e- → M●+ + 2e- M ●+ is the ionized analyte molecule called molecular ion Radical cation is formed by the loss of one electron Permits easy determination of molecular weight of analyte 5

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7. Basic Components of Mass Spectrometry 1. Sample Introduction System : Volatilizes the sample and introduces it to the ionization chamber under high vacuum 2. Ion Source Ionizes the sample (fragmentation may occur) and accelerates the particles into the mass analyzer 3 . Mass Analyzer (or Mass Separator) Separates ionized particles based on their mass-to-charge ratio (m/e-) 7

8. Basic Components of Mass Spectrometry 4 . Detector - Ion Collector Monitors the number of ions reaching detector per unit time as a current flow 5 . Signal Processor Amplifies the current signal and converts it to a DC Voltage 6. Vacuum Pump System A very high vacuum (10-4 to 10-7 torr) is required so that the generated ions are not deflected by collisions with internal gases 8

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10. I NSTRUMENTATION (1) Sample Introduction Systems Batch Inlet Direct Probe Chromatography Interface (GC-MS) Inductively Coupled Plasma (ICP) 10

11. Sample Introduction Systems I. Batch Inlet Sample is volatilized externally and allowed to “leak” into the ion source Good for gas and liquid samples with boiling points < 500 ° C II. Direct Probe Good for non-volatile liquids, thermally unstable compounds and solids Sample is held on a glass capillary tube, fine wire or small cup Sample Introduction System 11

12. Sample Introduction Systems III. Chromatography Interface (GC-MS) The MS is used both quantitatively and qualitatively Major interface problem – carrier gas dilution Jet separator (separates analyte from carrier gas ) IV. Inductively Coupled Plasma (ICP) Operates somewhat like a nebulizer in an AAS Also ionizes the sample in argon stream (at very high temperatures, >6000 °C) Only a small amount of analyte is utilized (< 1%) 12

13. Ion source Technologies Electron ionization C hemical ionization M atrix-assisted laser Desorption/ionization G low discharge F ield desorption (FD) fast atom bombardment (FAB) 13

14. Ion source technologies I . Electron ionization Electron ionization (EI, formerly known as electron impact) It is an ionization method in which energetic electrons interact with gas phase atoms or molecules to produce ions . This technique is widely used in mass spectrometry, particularly for gases and volatile organic molecule 14

15. Electron ionization The following gas phase reaction describes the electron ionization process : M + e- → M●+ + 2e- where M is the analyte molecule being ionized, e- is the electron and M+• is the resulting ion . 15

16. Chemical Ionization (CI) Ion Source A modified form of EI Higher gas pressure in ionization cavity (1 torr) Reagent gas (1000 to 10000-fold excess) added; usual choice is ethane, CH4 Reagent gas is directly ionized instead of analyte Gentle ; little fragmentation; even-electron ions produced more stable than odd-electron ions produced in EI Excess energy of excited ions removed by many ion-reagent gas collisions 16

17. Fast Atom Bombardment Ion source for biological molecules AR ions passed through low pressure AR gas to produce beam of neutral ions Atom-sample collisions produce ions as large as 25,000 Daltons 17

18. G low discharge Sputtering of the cathode material (the sample) by an argon plasma. Ionization of the elements of the sample in the plasma. Extraction and acceleration of ions. Ions separation with a magnetic sector Ions detection by a Faraday cup or an electron multiplier 18

19. Matrix-Assisted Laser Desorption/Ionization (MALDI) Analyte mixed with radiation-absorbing material and dried Sample ablated with pulsed laser Often coupled to time-of-flight (TOF) detector Excellent for larger molecules, e.g. peptides, polymers 19

20. Mass analyzer technologies Time-of-flight Quadrupole Quadrupole ion trap Linear quadrupole ion trap 20

21. Mass A nalyzer Technologies  Quadrupole Analyzer Ions forced to wiggle between four rods whose polarity is rapidly switched Small masses pass through at high frequency or low voltage; large masses at low frequency or high voltage Very compact, rapid (10 ms ) R = 700-800 21

22. Mass Analyzer Technologies B. TOF Time of Flight Mass Analyzer Separates ions based on flight time in drift tube Positive ions are produced in pulses and accelerated in an electric field (at the same frequency) All particles have the same kinetic energy Lighter ions reach the detector first Typical flight times are 1-30 µsec 22

23. Mass Analyzer Technologies B . Time of Flight Mass Analyzer Separation Principle : All particles have the same kinetic energy In terms of mass separation principles : Vparticle = Her/m Hold H,e , and r constant Vparticle = 1/m (constant) Vparticle is inversely proportional to mass 23

24. Detectors Monitors the number of ions reaching detector per unit time as a current flow The detection and recording of ions can be done either by photographic plates or electrical method. PHOTOGRAPHIC PLATES ELECTRICAL METHOD 24

25. Detectors (1) PHOTOGRAPHIC PLATES: In this method a photographic plate is kept at right angel to the path of ions so ions of successive m/e values form an image (2) ELECTRICAL METHOD: Detector is usually electron multiplier produce electrical signal proportional to number of ions, These signals are amplified by a series of dynodes. The result of these amplified signals is presented in the form of graph 25

26. Applications OF Mass Spectrometry in different fields drug discovery Clinical testing genomics environment geology 26

27. Mass spectrometry Role in Biochemistry Determine protein structure, function, folding and interactions Identify a protein from the mass of its peptide fragments Quantitate proteins in a given sample Monitor protein digestion 27

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