SELECTIVE ION-MOLECULE REACTIONS OF ETHER REAGENT IONS WITH NUCLEOSIDE ANTIBIOTICS IN A QUADRUPOLE ION-TRAP

The 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.