The fragment resulting from the loss of a single methyl group (M − 15) is often absent, and other fragments are often spaced by intervals of fourteen mass units, corresponding to sequential loss of CH2 groups.
O fragmento resultante da perda de só un grupo metilo (M-15) adoita estar ausente, e outros fragmentos adoitan estar espazados a intervalos de catorce unidades de masa, correspondendo á perda secuencial de grupos CH2.