Question

What is mass spectroscopy?

Answer 1

Mass spectroscopy is a method to find a molecule weight.

Explanation:

I'm not so familiar, sorry...

[Step 1] Molecules are ionized and crashes into fragments.
[Step2] Then, the ions are accelerated and induced into magnetic field.
[Step3] In the magnetic field, the ions are affected by Lorentz force `F(N)` and their obrit is bended.

`F=q(vxxB)` (`q(C)` the charge of ion: `v(m"/"s)`: velocity of ion, `xx`: cross product, `B(T)`: magnetic flux density).

And of course...
`F=ma` (m(`kg`): mass of ion, `a(m"/"s^2`): acceleration) and you can conclude:
`a=(q(vxxB))/m`

The point is that `color(red)"orbit of lighter ions or fractions are bended"`
`color(red)"more easily than that of hevier ions."`
Acceleration rate `a` is proportional to `q/m`.

[Step4] Sort ions or fractions by `m/q`(i.e. the reciprocal of `q/m`) and record the relative abundance of ions. This is how you can find a mass of the molecule or mass of fragments.

This is a mass spectrum for 1-phenyl-1-butanone(`C_6H_5COC_3H_7`). Cited from http://www2.odn.ne.jp/had26900/topics_&_items2/about_MS1.htm

What you can find from the result…
148: The mass of the whole molecule, and this is exactly the same as `C_6H_5COC_3H_7`.
77: The mass is same as the phenyl group, `C_6H_5-`. This implies that the molecule might have benzene ring.
105: `105-77=28` is the mass of carbonyl group(`-CO-`). Thus we can expect the molecule to have `C_6H_5CO-` group.