Mass spectrometry

mass spectroscopy

1. Presentation on:- Mass Spectrometry Presented by :- Vipin Jain M.Sc.(Pharmaceutical Chemistry) 2 nd sem

2. Contents :- Brief History of mass spectrometry Introduction Basic Principle Instrumentation Mass Spectrum Applications

3. Brief History of mass spectrometry 1913:- Thomson separates the  20 Ne and the  22 Ne isotopes, and he correctly identifies the  m/z  = 11 signal as a doubly charged  22 Ne particle. 1919:- Francis Aston constructs the first velocity focusing mass spectrograph. 1934:- Josef Mattauch and  Richard Herzog  develop the double-focusing mass spectrograph. 1946:- William Stephens presents the concept of a  time-of-flight  mass spectrometer. 1968:- Malcolm Dole  develops electrospray ionization. 2002:- John Bennett Fenn and  Koichi Tanaka  are awarded the Nobel Prize in chemistry "for the development of soft desorption ionisation methods for mass spectrometric analyses of biological macromolecules."

4. Introduction:- Mass spectrometry is a powerful analytical technique used to identify unknown compounds within a sample, and to elucidate the structure and chemical properties of different molecules. The complete process involves the conversion of the sample into gaseous ions, with or without fragmentation, which are then characterized by their mass to charge ratios (m/z) and relative abundances.

5. Basic Principle:- A mass spectrometer generates multiple ions from the sample under investigation, it then separates them according to their specific mass-to-charge ratio (m/z), and then records the relative abundance of each ion type. A mass spectrometer needs to perform three functions:- Creation of ions – the sample molecules are subjected to a high energy beam of electrons, converting some of them to ions. Separation of ions – as they are accelerated in an electric field, the ions are separated according to mass-to-charge ratio (m/z). Detection of ions – as each separated population of ions is generated, the spectrometer needs to qualify and quantify them.

6. An instrument that generates ions from molecules and measure their masses. The essential components of mass spectrometers:- SAMPLE INLET ION SOURCE ION ACCELERATOR ION ANALYSER ION DETECTOR signal COMPUTER MASS SPECTRUM Instrumentation:-

7. Sample Inlet System :- The purpose of the inlet system is permit introduction of a representative sample into the ion source with minimal loss of vacuum. Most modern mass spectrometers are equipped with several types of inlets to accommodate various kinds of sample ,these include: 1- Batch Inlet System ( Gas+ some liquid) 2- The Direct Probe Inlet ( Solid+ Liquid) 3- Chromatography and Capillary Electrophoretic Inlet System.

8. Ion Source :-   For producing gaseous ions from the substance being studied . Ways to produce ions:- Electron impact (EI) - vapor of sample is bombarded with electrons. M + e ====  2e + M . + + fragments 2) Chemical ionization (CI) - sample M collides with reagent ions present in excess e.g. CH 4 + e =====  CH 4 . + + CH 5 + M + CH 5 + ====  CH 4 + MH + 3) Fast Atom/Ion Bombardment (FAB):- Ionisation is brought by fast moving atoms. 4) Electrospray Ionization (ESI) - a stream of solution passes through a strong electric field (10 6 V/m).

9. The Electron-Impact Source :-

10. Chemical ionisation :- High Energy electrons  Sample Molecule MH  CH 4 CH 4 CH 4 + CH 3 + CH 2 + Molecule Ions 

11. Fast atom bombardment

12. Electrospray Ionisation

13. Electrostatic Acceleration System:- 1) The positive ions formed in the ionisation chamber are withdrawn by the electric field which exists between the first accelerator plate and the second repeller plate. 2) A strong electrostatic field between accelerator and repeller plate accelerates the ions of masses m 1 m 2 m 3... to their final velocities. 3) The ions which escape through slit having velocities and kinetic energies give. eV=1/2m 1 v 1 2 =1/2m 2 v 2 2 =1/2m 3 v 3 2 ......

14. Vacuum system: - 1) A high vacuum is to be maintained. 2) The inlet system is generally maintained at 0.015 torr, the ion source at 10 -15 torr and analyzer tube at 10 -7 torr or as low as possible. 3) Oil diffusion and mercury diffusion pumps are commonly used in different types of combination

15. Mass analyzers :- 1) S eparate ions based on their mass-to-charge ratio (m/z) 2) Operate under high vacuum (keeps ions from bumping into gas molecules) 3) Actually measure mass-to-charge ratio of ions (m/z) Types of mass analyzers :- 1) Quadrupole mass analyzer 2) Time of flight analyzer (TOF) 3) Magnetic sector mass analyzer a) Single focusing b) Double focusing 4) Quadrupole ion trap mass analyzer

16. Quadrupole mass analyzer:- 1) It consists of 4 voltage carrying rods. 2) The ions are pass from one end to another end 3) During this apply the radiofrequency and voltage complex oscillations will takes place. 4) Here the single positive charge ions shows the stable oscillation and the remaining the shows the unstable oscillations

17. Magnetic Sector Mass Analyzer:- In magnetic sector analyzers ions are accelerated through a flight tube, where the ions are separated by charge to mass ratios . m/z = B 2 R 2 / 2V

18. Time of flight analyzer :-

19. Detector: - 1) Electron multiplier :- Electron multipliers use a process known as secondary electron emission. 2) Faraday cup:- A Faraday cup is a metal (conductive) cup designed to catch charged particle in vacuum.

20. The mass spectrometer: -

21. Ion Abundance (as a %of Base peak) Mass, as m/z . Z is the charge, and for doubly charged ions (often seen in macromolecules), masses show up at half their proper value molecular ion Unit mass spacing Fragment Ions Derived from molecular ion or higher weight fragments Mass Spectrum :- A plot of the relative abundance of ions versus their mass-to-charge ratio (m/z).

22. Mass spectrum of propane:-

23. Applications :- 1) Pharmaceutical: drug discovery, combinatorial chemistry, pharmacokinetics, drug metabolism. 2) Clinical: neonatal screening, haemoglobin analysis, drug testing. 3) Environmental: PAHs, PCBs, water quality, food contamination. 4) Geological: oil composition. 4) Biotechnology: the analysis of proteins, peptides .

24. References :- Instrumental methods of chemical analysis by G.R.Chatwal www.omicsonline.org/mass-spectrometry wikipedia.org/wiki/ Mass_spectrometry www2.chemistry.msu.edu www.chemguide.co.uk

25. Thank you