Idealized fragmentation processes for the molecular ion M

a-Cleavage this involves breaking the next but one bond to a hetero-atom (N, 0, Hal, etc.) in the functional group of a molecule. The following examples illustrate the general principles  

(7-Bonds in alkanes C-C bonds break in preference to C-H bonds and the most stable carbocation will be formed as the base peak. For example, 2,2-dimethylpentane will give the stable (CHsIsC cation as the base peak instead of the less stable propyl cation CH3CH2CHJ. 

Aromatic compounds simple aromatics cleave to give a phenyl cation, m/z = 77, as the base peak which then loses ethyne to give m/z =51. Aromatics with CH2 next to the ring give the stable tropylium cation m/z = 91, and then lose ethyne to m/z = 65. I 

In both techniques the separated compounds from the chromatograph are sampled automatically and the mass spectrum of each compound is recorded. Comparison of the mass spectra with a library in an on-board database permits identification of the components of the mixture. 

Chromatography is used to separate the individual components of a mixture on the basis of differences in their physical characteristics, e.g. molecular size, shape, charge, volatility, solubility and/or adsorption properties. The essential components of a chromatographic system are  

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