Metal argide (MAr+) ions are lost during ion extraction in laser ablation-inductively coupled plasma-mass spectrometry

The abundance of metal argide (MAr+) ions during laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) is measured during ablation of pure samples of transition metals. As expected, the relative abundance of MAr+ ions to M+ ions for various elements increases as the dissociation energy (D-0) of the ion increases. Gas kinetic temperatures (T-gas) are determined from the calculated MAr+/M+ ratios and are used to indicate the origins of MAr+ ions. The determined T-gas values are very high, 8000 K to >= 20,000 K. which indicate that MAr+ ions are much less abundant in the mass spectrum than expected based upon plasma conditions. Collision-induced dissociation (CID) during the ion extraction process is suggested to be responsible for removal of MAr+ ions. Factors responsible for these collisions are discussed. (C) 2012 Elsevier B.V. All rights reserved.