Mass Spectrometer (MS) (steps 1 and 2)
The mass of atoms, molecules and fragments can be measured using a mass spectrometer.
1) All the air in the spectrometer is first pumped out.
2) A sample - element/compound - gaseous form - injected - MS + is bombarded with high-energy electrons - electron gun. If substance solid - heated too produce sufficient number of gaseous particles. Energy from the bombarding electrons strips electrons from the atoms/molecules, forming positive ions:
- A(g) + energy --> A+(g) + e- where A represents an atom
- M(g) + energy --> M+(g) + e- where M represents a molecule
+ions formed from molecules can fragment into 2 or more particles, 1 + and other neutral e.g. chlorine: Cl2(g) --> Cl2+(g) --> Cl+(g) + Cl(g) and from ethanol: C2H5OH(g) --> C2H5OH+(g) --> C2H5+(g) + OH(g) and C2H5OH(g) --> C2H5OH+(g) --> C2H5+(g) + OH(g)
Mess Spec (steps 3, 4 and 5)
3) +ions accelerated by high electric potential, pass through slits + emerge as a parallel beam of ions. All ions have same energy so those of a particular mass have the same speed
4) Ions - deflected by powerful magnetic feild - those with greater mass: deflected less than those of a smaller mass. Ions sorted according to mass. Angle deflected depends upon the strength of magnetic feild and the mass-to-charge ratio (m/e) of the ion.
5) Ions of lowest mass - deflected first. Magnetic feild gradually increased + ions of greater mass are then deflected. Detector couple to computer and calculates the m/e ratio of each +ion and relative abundance compared with the most abundant particle. Converted to % for each +ion
- bombardment - by high energy electons to create +ion
- acceleration - of +ions by an electric potential
- deflection - of +ions by a magnetic feild
- detection - of +ions
B . A . D . D = BIG APPLES DON'T DIE
Uses of Mass Spectrometers
Data can be obtained from mass spect od calculate RAM of an element
WORK IT OUT:
R.A.M = (m/e x %) + (m/e x %) = anwser ---> anwser/100 == R.A.M
- Detection of drugs in urine samples
- In the pharmaceutical industry
- Carbon-14 dating