Question

How do gaseous and desorption ionization sources differ? what are the advantages of each?

Answer 1

In gaseous sources the sample is first vapourized and then ionised.
In desorption sources, the liquid or solid state sample is directly converted into gaseous ions.

The advantage of gaseous sources is that it is used to ionize thermally stable compounds.
The advantage of desorption sources is that it is used to ionize non volatile and thermally unstable samples.