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Mass spectroscopy.pptx
- 2. The definition of a mass spectrometer may seem simple: it is an instrument that can ionize a sample and measure the masstocharge ratio of the resulting ions. This versatility arises from the fact that mass spectrometers can give qualitative and quantitative information on the elemental, isotopic, and molecular composition of organic and inorganic samples furthermore, samples can be analyzed from the gas, liquid, or solid state, and the masses that can be studied range from single atoms (several Da) to proteins (over 300,000 Da) J. J. Thompson constructed the first mass spectrometer in 1912. The early mass spectrometers were primarily used by physicists to study the atomic weight of the elements and the natural relative abundance of elemental isotopes .
- 4. Stage 1 Ionisation Electro Ionisation is the most common type of ionisation. The sample is bombarded by electrons which come from a heated filament. The electrons run in a stream between the cathode and anode. When the sample passes through the electron stream, the high energy electrons in the stream knock electrons out of the sample to form ions.
- 5. Stage 2 Acceleration Acceleration is a simple step where the ions are placed between a set of charges parallel plates. The ions will then be repelled by one plate and attracted to the other. There is a slit cut in the plate which the ions are attracted to. the force of attraction and repulsion forces the ions through the slit at an accelerated rate. The speed of acceleration can be adjusted by changing the charge on the plates.
- 6. Stage 3 Deflection ions are deflected by the magnetic field surrounding the instrument. The amount of deflection depends on the mass and charge of the ions. The heavier ions and ions with a positive charge of 2 or more, are deflected the least (Ion stream C) The lightest ions and ions with 1 positive charge are deflected the most (Ion Stream A) The ions at the correct mass and charge travel to the detector. (Ion Stream B) The mass to charge ratio (m/z) is determined from the ion that hits the detector
- 7. When the ion stream reached the detector the hit a wire. On hitting the wire they become neutralised by an electron jumping from the metal wire to the ion. The amplifier picks up on this current being created between the wire and the ion and amplifies the signal being detected. The computer picks up on this and converts it to mass/charge ratio and a spectrum is produced.
- 8. Applications of Mass Spectrometry Mass Spectrometry as a technique can be coupled with other techniques such as HPLC and GC. As it is used in the identification of compounds it is used in all areas of science. Some of its uses are: 1.Trace Gas Analysis 2.Pharmaceutical Industry 3.Space Exploration 4.Forensic Toxicology 5.Archaeological Dating.