Determination of arsenic, iron and selenium in moss samples using hexapole collision cell, inductively coupled plasma-mass spectrometry

Different collision gases (H-2, He and premixed 7% H-2 in He) used in the hexapole collision cell of an inductively coupled plasma-mass spectrometer (ICP-MS) were compared, and the gas-flow rates were optimized for the determination of arsenic (As-75), iron (Fe-56) and selenium (Se-80). The study showed that the argon-based interferences at mass-to-charge ratios (m/z) of 56, 75 and 80 can be overcome by the optimized gas flows (7.5 ml min(-1) premixed 7% HZ in H-2 and 2 ml min(-1) HZ) in the hexapole collision cell. Detection limits of 15.5 ng l(-1) for iron (Fe-56) and 29 ng l(-1) for selenium (Se-80) in 2% (v/v) HNO3 were obtained under optimized collision cell conditions. The detection limit for arsenic (As-75) obtained in difficult hydrochloride acid matrix (5% HCl (v/v)) was 153 ng l(-1). The accuracy of the optimized method was confirmed by analyzing two moss reference materials. The results obtained by ICP-MS for arsenic, selenium and iron from both moss reference samples were, in most cases, in good agreement with the certified values. (C) 2003 Elsevier B.V. All rights reserved.