Two competing ionization processes in ESI-MS analysis of N-(1,3-diphenylallyl)benzenamines: formation of the unusual [M-H]+ ion versus the regular [M+H]+ ion

Liwen Fang; Cheng Dong; Cheng Guo; Jianxing Xu; Qiaoling Liu; Zhirong Qu; Kezhi Jiang

doi:10.1177/1469066717717228

Two competing ionization processes in ESI-MS analysis of N-(1,3-diphenylallyl)benzenamines: formation of the unusual [M-H]⁺ ion versus the regular [M+H]⁺ ion

Eur J Mass Spectrom (Chichester). 2018 Jun;24(3):251-260. doi: 10.1177/1469066717717228. Epub 2017 Jul 5.

Authors

Liwen Fang¹, Cheng Dong¹, Cheng Guo², Jianxing Xu¹, Qiaoling Liu¹, Zhirong Qu¹, Kezhi Jiang¹

Affiliations

¹ 1 Key Laboratory of Organosilicon Chemistry and Material Technology, Hangzhou Normal University, Hangzhou, China.
² 2 Cancer Institute, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.

PMID: 29232977
DOI: 10.1177/1469066717717228

Abstract

A series of N-(1,3-diphenylallyl)benzenamine derivatives (M) were investigated by electrospray ionization mass spectrometry in the positive-ion mode. Both the anomalous [M-H]⁺ and the regular [M+H]⁺ were observed in the ESI mass spectra. The occurrence of [M-H]⁺ has been supported by accurate mass spectrometry, liquid chromatography mass spectrometry, and tandem mass spectrometry analysis. Calculation results indicated that formation of [M-H]⁺ is attributed to the ion-molecule reaction of M with the protonated ESI solvent molecule (e.g. CH₃OH₂⁺) via hydride abstraction from a tertiary C_sp3-H. The competing ionization processes leading to [M-H]⁺ or [M+H]⁺ were significantly affected by the concentration of formic acid in the electrospray ionization solvent and the proton affinity of the N atom.

Keywords: 3-diphenylallyl)benzenamine; N-(1; [M−H]+; electrospray ionization mass spectrometry; two competing ionization processes.