エレクトロスプレー帯電水滴衝撃による脱離イオン化メカニズム

概要

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Electrospray droplet impact (EDI) secondary ion mass spectrometry (SIMS) is a desorption/ionization technique for mass spectrometry. Highly charged water clusters produced via atmospheric-pressure electrospray are accelerated in a vacuum at several kV and impact the sample, which is deposited on a metal substrate. Two mechanisms for desorption/ionization in the EDI ionization process have been proposed, namely, low-energy and high-energy regimes. In the low-energy regime, the excess charges in the primary droplets play a role in the formation of secondary ions. In the high-energy regime, samples are ionized as the result of the supersonic collision of the primary droplets with the sample. In general, EDI/SIMS is very effective for the formation of [M+H]+ and [M−H]− for a wide variety of molecules. This characteristic of EDI/SIMS is probably due to the formation of the highly acidic H3O+ and highly basic OH− ions, which are superb protonating and deprotonating reagents, respectively. In addtion, EDI produces a much smaller number of hydrogen atoms compared with matrix-assisted laser desorption/ionization (MALDI) and fast atom bombardment (FAB).