Mass spectrometry is a powerful technique used to identify the molecules in compounds, either gas, solid or liquid, and specifically how many of each molecule type is present and the structure of molecules (what atoms make up the molecule and how the atoms are arranged). To do this, mass spectrometry involves firstly ionising the compounds so as to have electrically charged ions which will be measured for their mass-to-charge ratios. You also need a mass spectrometer.
How a mass spectrometer works
Mass spectrometry is important for analysing efficiently and accurately in various scientific domains, such as physics, biology, chemistry and biochemistry. Basically, the sample to be analysed, if not already so, must be vaporised to make it gaseous.
The gas is bombarded with electrons so that the molecules become electrically charged ions, which are accelerated down a tube. Then they go through the analyser with its electric or magnetic field, which deflects the ions according to their weight. How much the ions are deflected depends on the ions’ mass and their own magnetic charge.
The beams of ions are detected by the detector at the end. A computer analyses the data collected here and shows a graph with the results – the mass spectrum. Only one beam of ions goes through to the analyser and detector, but to gather other results, the scientist adjusts the magnetic field’s intensity.
There are different versions of mass spectrometers, but quadrupoles are used for a wide range of analysing options and have been developed to target different applications. A quadrupole analyser is made up of four metal rods in parallel. The analyser sorts the ions using radio-frequency and DC (direct current) and when this filter strength is changed, different weight ions go through to the detector.
For different mass spec jobs there are single, tandem, and triple quadrupoles.
Applications for mass spectrometers
The applications have a wide range such as pharmaceutical and environmental analysis. Drugs discovery and development depends on these instruments. The food safety industry can measure pesticide residues in food. Clinical chemists use mass spectrometry for neonatal screening and drug tests.
Astronomers can determine the isotopes and elements in solar wind, while biologists discover the structure of complex molecules, or geologists can locate oil deposits in rocks, for example. The list is almost endless and mass spectrometers are becoming as important as x-ray machines.
Picture: paolo toscani – Fotolia