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 ( 75 As ), iron ( 56 Fe ) and selenium ( 80 Se ). 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% H 2 in He and 2 ml min −1 H 2) in the hexapole collision cell. Detection limits of 15.5 ng l −1 for iron ( 56 Fe ) and 29 ng l −1 for selenium ( 80 Se ) in 2% (v/v) HNO 3 were obtained under optimized collision cell conditions. The detection limit for arsenic ( 75 As ) 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.