Laser ablation generation of cluster ions from concentrated sulfuric and selenic acids

Abstract

Abstract The generation and identification of novel homo‐ and hetero‐polyacid clusters was achieved using a standard matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometer. The formation of several singly charged species was achieved via the interaction of a laser beam with concentrated sulfuric acid, selenic acid or their mixtures, applied on a graphite microcrucible. A higher yield of the species was observed in the negative detection mode, where sulfuric acid adducts HSO · m H 2 SO 4 ( m = 0–3) and HSO · m H 2 SO 4 · SO 3 ( m = 1, 2), and selenic acid adducts HSeO , HSeO · X (X = SeO 3 , H 2 SeO 4 , 2SeO 3 , H 2 SO 4 · SeO 3 ) and NaSeO · Y (Y = H 2 SeO 4 , H 2 SeO 4 · SeO 3 , 2H 2 SO 4 , H 2 SeO 4 · 2SeO 3 , 2H 2 SeO 4 · SeO 3 , 3H 2 SeO 4 ), were identified. In the mass spectra of the mixture of acids, besides the homo‐polyacidic adducts, eleven mixed species containing both sulfuric and selenic acid molecules or ions were identified, of which the heaviest was found to correspond to NaSeO · H 2 SeO 4 · 3SO 3 . The stoichiometry of the species was confirmed using isotopic pattern modeling. Copyright © 2005 John Wiley & Sons, Ltd.