📝 Mass spectrometry

Task

🎧️ Listen to the recording and mind pronunciation of words.

Mass spectrometry is an analytical technique that can be used to deduce the molecular formula of an unknown compound. Gaseous molecules of the compound are bombarded with high-speed electrons from an electron gun. These knock out an electron from some of the molecules, creating molecular ions (M⁺), which travel to the detector plates. The relative abundances of the detected ions form a mass spectrum: a kind of molecular fingerprint that can be identified by a computer using a spectral database. The peak with the highest mass-to-charge ratio (m/z) is formed by the heaviest ion that passes through the spectrometer. This value of m/z is equal to the relative molecular mass of the compound.
High – resolution mass spectrometry can be used to determine the molecular formula of a compound from the accurate mass of the molecular ion.
A molecular ion is a positively charged ion, which is also a radical as it contains a single unpaired electron. It is therefore sometimes represented as M⁺•. During mass spectroscopy, the molecular ion can fragment into a positive ion and a radical.
This fragmentation process gives rise to characteristic peaks on a mass spectrum that can give information about the structure of the molecule.
Some uses of mass spectrometry include:

• Identifying elements in new or foreign substances, for example analysing samples from the Mars space probe.
• Monitoring levels of environmental pollution for example amounts of lead or pesticide in a sample.
• In biochemical research, for example, determining the composition of protein by comparing it against a database of known compounds.

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