Study of Endocrine Disruptor Octylphenol Isomers Using Collision-Induced Dissociation Mass Spectrometry

Abstract

Fragmentation processes of molecular-related ions M^+· and [M-H]^- of phenolic endocrine disruptors, 4-n-octylphenol, 4-(1,1,3,3-tetramethyl-butyl)phenol, and 4-(1-ethyl-1-methyl-butyl)phenol, which are octylphenol isomers, have been studied using high- and low-energy collision-induced dissociation (CID) mass spectrometry. The product ion spectra revealed the isomeric structures of octyl group C₈H₁₇ found in CID studies of both precursor ions, M^+· and [M-H]^-. The high-energy CID spectra of the deprotonated molecules [M-H]^- were compared with the corresponding low-energy CID spectra. Although the fragmentation pattern of low-energy CID differed markedly from that of high-energy CID, both product ion spectra were useful in identifying the isomeric structures of the octyl group. The negative-ion products from the precursor [M-H]^- could be explained by two mechanisms with homolytic cleavage, called charge-remote fragmentation (CRF), while the positive-ion products from M^+· were understood as homolytic radical-initiated fragmentation (RIF) and heterolytic charge-initiated fragmentation (CIF).