Analysis of Methyl-,Chloro-,Bromo- and Trifluoromethyl-Substituted 1,9-Diphenyl-9H-Fluorene and its Isomers by Gas Chromatography-Ion Trap Multistage Tandem Mass Spectrometry

Abstract

This work presents a modified method to analyze methyl-, chloro-, bromo- and trifluoromethyl-substituted 1,9-diphenyl-9H-fluorene and their isomers by ion trap mass spectrometry with electron impact ionization (EI). Since MS spectra of 1,9-diphenyl-9H-fluorene with these four groups and their isomers are similar, it is difficult to distinguish them from its isomers. Multistage tandem mass spectrometry analysis involves selecting molecular ions obtained in MS spectra as precursor ions in the MS/MS process, and the fragment [C₂₅H₁₇]⁺ (m/z 317) obtained in MS/MS spectra as a precursor ion in MS³ processes. Collision-induced dissociation (CID) experiments at different activation energies were done to elucidate possible fragmentation pathways. Proposed fragmentation pathways including m/z 317 and structures of the product ions are acquired simultaneously. At a higher CID voltage, the isomers of C₂₅H₁₇–CF₃ can be distinguished in MS/MS, while the isomers of C₂₅H₁₇–CH₃, C₂₅H₁₇–Cl and C₂₅H₁₇–Br can be distinguished in MS³. This work can provide new and valuable information needed for unambiguous characterization of such substances in complex sample matrices.