Selective ion–molecule reactions of ether reagent ions with nucleoside antibiotics in a quadrupole ion trap

Abstract

AbstractThe analysis of a targeted group of nucleoside antibiotics has been accomplished through the use of selective ion‐molecule reactions and collision‐activated dissociation (CAD) techniques in a quadrupole ion trap. A series of homologous ether reagent ions generated from dimethyl ether, di‐n‐butyl ether and 2‐methoxyethanol were used as chemical ionization reagents. Because chemical ionization with dimethyl ether and di‐n‐butyl ether reagent ions did not provide selectivity and signal enhancement for the analysis of these biopharmaceuticals, a chemical ionization reagent with special hydrogen‐bonding capabilities was used. The reagent ion that showed the greatest promise is a product of 2‐methoxyethanol, CH3OCH2CH2OCH2 +. This highly reactive species, which reacts selectively with nitrogen‐containing compounds, can undergo both nucleophilic attack and anchoring via hydrogen bond formation between the methoxy oxygen and an acidic hydrogen of the nucleoside substrate. The reaction of the CH3OCH2CH2OCH2+ ion with each of the nucleoside antibiotics resulted in formation of [M + 13]+ and [M + 89]+ products. The CAD spectra indicated that the adducts are covalently bound species and that the nucleotide moiety dominates both the reactive and dissociative behavior of the nucleoside antibiotics.