Question

How to do you generate mass spectroscopy of an unknown compound? Please give detailed step by step instructions.

Answer 1

Mass Spectroscopy:

It is an analytical tool primarily concerned with the separation of molecular & atomic species according to their mass.

Steps:

I) Atom or molecule is hit by high energy electron.Electron is deflected but transfer its energy to the molecule.

II) This energy rich species ejects electron forming positively charged ion known as molecular ion.

III) Molecular ion is deflected by magnetic field . Amount of deflection depends on m/z or m/e ratio.Higher m/z deflected less & lower m/z deflected most.

IV) A plot of the relative abundance of the ions versus m/z ratio is known as mass spectrum. The most abundant peak is known as base peak.

Component Of mass spectrometer:

Sample Inlet Ion source   Ion analyser Ion detector Computer Mass spectrum

The most important step in mass spectrometer is mass ionization which involves four methods:

1.Electron Ionisation: most common technique but limited to low MW compounds(<600 amu)

2.Chemical Ionisation: soft ionisation gives little fragmentation& for low MW compounds(<800 amu)

3.Desorption Ionisation: For higher MW & labile compounds.

4.Spray Ionisation:  Generally applicable forb biomolecules.