Reduction of polyatomic interferences during ion-chromatographic speciation of metal ions via their EDTA complexes along with ICP-MS detection using an octopole reaction system

Abstract

Metal ions, in the form of their EDTA complexes, can be separated and determined by ion chromatography coupled to inductively coupled plasma mass spectrometry (ICP-MS). However, polyatomic interferences can occur during ICP-MS process and this requires techniques for removing or reducing them. ICP-MS combined with an octopole reaction system was used to reduce polyatomic interferences during the detection of metal ions (55Mn, 56Fe, 59Co, 60Ni, 63Cu, 64Zn, 208Pb) as their EDTA complexes followed by the separation of IC. The results indicated that polyatomic interferences can be reduced for the detection of 56Fe, 60Ni, 63Cu and 64Zn if either helium or hydrogen gas was added to the collision/reaction cell. Hydrogen was preferred since it resulted in higher sensitivity and lower background intensity. The separation of seven metal ions was achieved on an anion-exchange column within 7 min using diammoniumhydrogen phosphate buffer of pH 7.5 as the mobile phase. The detection limits were in the range of 0.1–0.5 μg L−1 with the exception of Fe (5.0 μg L−1) if hydrogen was the reaction gas. The method was applied to the determination of metal ions in natural water samples.