Figure 1

Full-scan and tandem mass spectra of the [M + 16]⁺ ion of toluene (a-1, a-2) under APCI conditions; and breakdown curves generated by abundances of selected fragment ions versus excitation amplitudes of the [M + 16]⁺ ion of toluene (b-1) and three positional protonated toluidine (b-2, b-3 and b-4).