Mass Spectrometry

Mass Spectrometry

Mass Spectrometry is used to determine the relative abundances of isotopes in nature. Mass spectrometry ionizes atoms and molecules with high beam of energy and then passes the ions through a magnetic field based on the mass to charge ratio of the ion. The mass spectrum of a sample shows the relative abundance of each ion.

In a mass spetrometer, a sample of atoms or molecules in inserted into the instrument. The sample is usually in an aqeuous or organic solution and is immediately vaporized by a heater in the device. The vaporized sample is then hit by high-energy electrons which are strong enough to knock electrons off atoms in the sample. This creates cationic versions of the sample that are accelerated through the magnetic field.

Once the ions enter the magnetic field, they are deflected into different amounts based on their charge and speed. The heavier ions that move more slowly are deflected less and the lighter ions that more more quickly are deflected more. The higher the charge of the ion, the more likely it will be deflected. The mass to charge ratio of the ions is inversely proportional to the mount that the ions are deflected. The detector records values and amounts for each ion; the relative abundance for a specific type of ion within the sample can be determined by dividing the number of ions of that type by the total number of ions detected. The mass spectrometer then creates a mass spectrum for the sample which marks the relative abundance of the ion against the mass-to-charge ratio of the ion.

A form of mass spectrometry has been used since the 1970’s to improve the accuracy of radiocarbon dating for archaeologists. Accelerator mass spectrometry accelerates ions to high speeds before analyzing their mass and counts individual Carbon-14 atoms. This allows smaller objects to be dated accurately. Mass spectrometry can also be used by the FDA to determine the amount of pesticides in food and limit the amount of pesticides that enter the food supply.

Works Cited:
http://www.iop.org/resources/topic/archive/archeology/
https://www.khanacademy.org/science/chemistry/atomic-structure-and-properties/mass-spectrometry/a/isotopes-and-mass-spectrometry
https://phys.org/news/2010-02-mass-spectrometry.html
https://www.youtube.com/watch?v=tOGM2gOHKPc