Negative‐ion mass spectrometry of substituted adenine bases and adenosine nucleosides

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Abstract
The negative-ion chemical ionization (ammonia, 5 Pa source pressure) mass spectra of a series of substituted adenine bases, adenosine nucleosides, and the trimethylsilyl derivatives of the nucleosides are described. Selected ions from these spectra were subject to collisionally activated dissociation with mass-analysed ion kinetic energy (CAD/MIKE) analysis of the products and the spectra assessed for information content. In addition to observing strong peaks due to quasimolecular ions and heterocyclic-base ions, it proved possible to differentiate between 2′-, 3′- and 5′-deoxy and between 2′- and 3′-O-methyl isomers. The negative-ion chemical ionization spectra of four methyladenines are essentially identical, but could be clearly distinguished from each other by CAD/MIKE analysis.