How do mass spectrometers work?

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How can a machine tell you the composition of something??

In: Chemistry

4 Answers

Anonymous 0 Comments


Anonymous 0 Comments

Here’s your sample. Hit it with something mildly energetic, like a beam of electrons. Some of the sample’s atom and molecules will be kicked off, and ionized (lose an electron). There ions have a positive charge, and can be accelerated by an electric field. This stream of sample ions is then exposed To a magnetic field. The field causes the stream to bend into an arc ( for reasons. Trust me.) But the heavier bits are not bent as much as the light bits, so the stream spreads out into a fan with bits distributed according to their masses. Then you detect all these spread-out bits, and the data is the mass spectrum.

You can use this mass data to figure out exactly what kind of atoms and molecules came from the sample.

Anonymous 0 Comments

This one is a hard ELI5 because you need to know some foundational physics for it to make sense. But, a mass spectrometer analyzes the mass/charge ratio of ionized molecules. That ratio is very specific to each element.

Anonymous 0 Comments

you can think of a mass spectrometer as a super expensive fancy scale. it’s expensive and fancy because instead of lbs or kgs, it measures the mass-to-charge ratio (m/z) of whatever you throw n there. there are different kinds of mass specs, but generally there are 3 components: the ion source, mass analyzer, and detector. the idea is you zap a sample via the ion source (e.g. by electrospray ionization, matrix-assisted laser desorption/ionization etc.), the mass analyzer sorts ions by their mass-to-charge ratio (time-of-flight, Fourier transform ion cyclotron resonance, etc), and the detector records the signal that becomes the mass spectrum (plotted as intensity of detected ions as a function of the m/z ratio). once you have your mass spectrum, you can identify what’s in your sample by correlating known masses to the masses in the sample, or by analyzing the ion fragmentation patterns. other compound separation methods are often used with mass spec (like liquid/gas chromatography, UV spectroscopy etc) to further separate the components of a sample you’re trying to study.

this is a huge oversimplification of mass spec because this rabbit hole goes deep