Flavone as a novel matrix for the MALDI analysis of lanthanide and transition metal salts

The mass spectral analysis of metal salts, especially lanthanide and transition metal salts can be challenging. Although getting information on the metal present is usually straightforward, obtaining information on the correct oxidation state and anion composition is challenging. Many ionisation techniques have some redox component to the ionisation process which commonly results in changing the oxidation state of the metal and the associated loss of ligand and anion information. We present here a simple method for negative ion matrix-assisted laser desorption/ionisation mass spectrometry using the non-acidic flavonoid flavone as a novel matrix. This results in reliable information on the oxidation state of the metal as spectra are dominated by anion adduct ions with very little (typically no) redox processes occurring.