Fully automated exact mass measurements by high-resolution electrospray ionization on a sector instrument

A method for the automated acquisition of exact mass measurements on the molecular ions of small-to-medium molecular weight organic compounds (200–2000 Da) is described. Molecular ions were generated by electrospray ionization (ESI) in either positive-ion (ES+) or negative-ion (ES−) mode, using a sector mass spectrometer under high-resolution conditions. Exact mass measurements were obtained by bracketting the molecular ion with ions from a reference compound, which was introduced into the instrument simultaneously with the sample. Scan setup, sample injection, data acquisition and post-acquisition processing, including output of final results, were fully automated and controlled by procedures supplied with the instrument. Results obtained by ES+ and ES− for a typical sample compound are presented and assessed.