Mass Spectral Fragmentation Pathways of Phthalate Esters by Gas Chromatography–Tandem Mass Spectrometry

Gas chromatography–tandem mass spectrometry was applied to study the mass spectral fragmentation of phthalate esters. The base peaks of phthalate esters with alkyl side chains (except dimethyl phthalate) were m/z 149, indicating that their fragmentation pathways were similar. The base peaks of benzyl butyl phthalate and dibutoxyethyl phthalate were also at m/z 149. Because of the presence of benzyl groups and butoxy groups in the side chains, their mass spectral fragmentation pathways were different from those of phthalate esters with alkyl side chains. The base peaks of dimethyl phthalate and diphenyl phthalate were m/z 163 and m/z 225, respectively, which corresponded to the fragments produced by α-cleavage of their molecular ion peaks. The base peaks of dimethoxyethyl phthalate and diethoxyethyl phthalate were m/z 59 and m/z 72, respectively, which corresponded to fragments produced by McLafferty rearrangement of their molecular ions. The fragmentation pathways provide fundamental information for the determination of phthalate esters and their metabolites.