Formation of complexes with divalent ions as a means of extending the mass scale in field desorption mass spectrometry

Cationization of polyethyleneglycols with [Ca]2+ ions prior to field desorption mass spectrometry gives abundant [M + Ca]2+ ions in approximate proportion to the species present. Similar treatment with [Ba]2+ converts sucrose, raffinose and stachyose into doubly charged complex ions, including [M + Ba]2+. Such doubly charged ions extend the effective mass range of conventional mass spectrometers without the inherent loss of sensitivity associated with reduced accelerating voltage.