Cation attachment in the analysis of polystyrene and polyethylene glycol by laser‐desorption time‐of‐flight mass spectrometry

Abstract

Al⁺, Cr⁺ and Cu⁺ gas‐phase ions have found to attach effciently to two polymers, polystyrene and polyethylene glycol (PEG) in laser‐desorption time‐of‐flight experiment, and are shown to be viable alternatives to be commonly used Na⁺, K⁺ and Ag⁺ ions. At high laser powers, in the range 8.0 × 10⁷ to 2.0 × 10⁸ W/cm², ions can be attached by desorption from a support made of the apporoptite meal. An alternative method is to add the metal ion in the form of a salt containing the metal in the +1 oxidation state, when such salt are available. This method requires lowe laser powers, in the range 2.0 × 10⁷ to 8.0 × 10⁷ W/cm². The two desorption/attachment methods are characterized by different optiomal time‐delay values for recording of spectra. Polystyrence has been found to have a hight affinity for attachemnt to Al⁺, Cr⁺, and Cu⁺ than to K⁺, while PEG has ben found to have a hight affinity for K⁺ than for Al⁺, Cr⁺. These preferential attachments are discussed in terms of the hard and soft acids and bases principle.