Mehul Bhardwaj 2008BB50021
Table of Contents:
1. Introduction What is Mass Spectroscopy? Operating principle Steps 2. Application in Combinatorial Biotechnology Advantages/ summary 3. References 3 3 4 4 6 7 9
Mass spectrometry’s is one of the most important analytical methods, due to its outstanding characteristics such as, high sensitivity, detection limits, speed and ease of handling. Also, it can be used in various fields of science, such as analytical chemistry, pharmaceutical industry, environmental chemistry, forensic sciences etc. In analytical chemistry, it has been recently found useful in biochemical problems like proteome, metabolome, drug discovery, metabolism and so on. It has also been used to detect soil, water and food contamination and thus is a handy tool for environmental studies. Other applications include atomic physics, reaction physics, reaction kinetics, geochronology, inorganic chemical analysis, ion–molecule reactions, determination of thermodynamic parameters (Gibbs free energy, Ka, etc.), and many others.
What is Mass Spectroscopy?
A simple definition of mass spectroscopy would describe it as a method to weigh molecules by measuring the mass-to-charge ratio (m/z) of its ions. Thus, the first step in any mass spectrometer would include the ionizing if the molecules. This step should not break down the molecule or affect any other properties, but should only add a desired amount of charge (and known mass) to the molecule under investigation. The ions are then made to enter a zone, a certain mass analyzer, in which a certain electrostatic and magnetic potential exists. This zone is where the separation of molecules on the basis of m/z ratio takes place. The ions are finally detected at the end of the mass analyzer tunnel using suitable methods.
The ability of this technique to measure masses as small as 1 Da, is what makes it so useful in identifying and quantifying various molecules such as novel proteins, peptides, drug candidates, synthetic chemicals and polymers etc.
The fundamental principle on which a mass spectrometer works is by manipulating the flight of various ions to be detected by applying a certain magnetic field. Without going into the physics of how a magnetic field affects a charge particle by giving it a velocity, it is sufficient to understand here that depending upon the m/z ratio the ions travel differently in the mass analyzer tube, and hence get detected at different time interval. By knowing the magnetic field applied, length and bend of mass analyzer tunnel, charge on subject ion, and time of flight, the mass of the subject molecule can be easily calculated. The particles are ionized because then their flight easier to manipulate using electric and magnetic fields.
Ionization can be carried in the following ways: • Electrospray(ESI) • • • • • MALDI (Matrix Assisted Laser Desorption & Ionisation) Electron Impact (EI) Chemical Ionization (CI) Atmospheric Pressure Chemical Ionization (APCI) Photo‐ionization (APPI)
MALDI and ESI are now the most common ionization sources for bimolecular mass spectrometry, offering excellent mass range and sensitivity
Even the Mass Analyzer can be of different types namely: • Linear Quadruple • • • • Time‐of‐Flight Sector Ion Trap FTICR ( Fourier Transform Ion Cyclotron Resonance)
Then the ions can again be detected by 4 major methods: • Faraday Cup • • • Discrete Dynode Continuous Dynode Multi‐channel Plate
The combination of these can give rise to various types of Mass Spectrometers, but only some combinations are actually of use. Some of the examples are MALDI-TOF, ESI-Quad etc. Thus the steps can be summarized as follows: Ionize the sample using a suitable source.
Use a mass anaylzer to separate the ions according to their m/z ratio. A second mass analyzer...