Unique Structural Information Obtained from Metal Adducts on Mass Spectrometry

Abstract

On electrospray ionization-mass spectrometry (ESI-MS), several adduct ions such as [M+H]⁺, [M+NH₄]⁺, [M+CH₃COO]^-, [M+Na]⁺, and [M+K]⁺ are observed. Among them, metal adduct ions have been recently focusing for their characteristics that provides unique fragmentation. A coordination position of metal ion is totally different from H⁺ and NH₄ ⁺, and the coordination is considered to be based on cation-π electron interaction. Coordination of metal ion brings the changes of some geometric parameters and binding energies of the ion, which results in strikingly different fragmentation from that of [M+H]⁺ and [M+NH₄]⁺. In this review, we introduced the mechanisms about coordination of metal ion and some examples of structural analysis focusing on lipid.