MASS SPECTROSCOPY

Mass spectrometer converts molecules to ions under vacuum so that they can be moved about and manipulated by external electric and magnetic fields.
These ions are then separated and determined. Separation is achieved on different trajectories of moving ions in electrical and/or magnetic fields.
*Electrospray Ionization (ESI)
*Matrix-Assisted Laser Desorption/Ionization (MALDI)
*Time-of-Flight (TOF) Mass Analyzer
Recent advances in the application of mass spectrometry in food-related analysis
*LC-MS coupling techniques
*HPLC-MS coupling techniques
*MALDI-TOF-MS
*ESI-MS

1. MASS SPECTROSCOPY - Meesha Singh

2. Introduction Basic Principle : Mass spectrometer converts molecules to ions under vacuum so that they can be moved about and manipulated by external electric and magnetic fields. These ions are then separated and determined. Separation is achieved on different trajectories of moving ions in electrical and/or magnetic fields. Associated components : A small sample of compound is ionized, usually to cations by loss of an electron- The lon Source The ions are sorted and separated according to their mass and charge. - The Mass Analyzer The separated ions are then detected and tallied, and the results are displayed on a chart.- The Detector

3. Instrumentation

4. Soft Ionization Techniques Electrospray Ionization (ESI) Spray sample solution from a needle into an orifice in the interface across a high potential difference. Heat and gas flows: to desolvate the ions existing in the sample solution. It can produce multiple charged ions with the number of charges tending to increase as the molecular weight increases. Extremely useful for accurate mass measurement, particularly for thermally labile, high molecular mass substances ( ie . proteins, oligonucleotides , synthetic polymers, etc.)

5. Matrix-Assisted Laser Desorption/Ionization (MALDI) Dissolve analyte in a solution containing an excess of a matrix such as sinapinic acid or dihydroxybenzoic acid. Such matrix has a chromophore that absorbs at the laser wavelength. Place a small amount of this solution is placed on the laser target. The matrix absorbs the energy from the laser pulse and produces a plasma that results in vaporization and ionization of the analyte . Rapid and convenient molecular weight determination.

6. Time-of-Flight (TOF) Mass Analyzer For an ion accelerated by voltage V, the resulting velocity is proportional to the mass-to-charge ratio. In a Time-of-flight (TOF) mass spectrometer, ions are detected on the basis of the time needed to travel a path L. Ions of very high mass-to-charge (several hundreds of kD ) may be recorded after an appropriate length of time. Fastest available MS analyzer Well suited for pulsed ionization methods Highest practical mass range of all MS analyzers.

7. Recent advances in the application of mass spectrometry in food-related analysis

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