Avoidance of spectral interference on europium in inductively coupled plasma mass spectrometry by sensitive measurement of the doubly charged ion

Abstract

Low-level rare earth element (REE) determination is becoming increasingly important in a number of scientific areas. In general, the determination of REE by inductively coupled plasma mass spectrometry (ICP-MS) is straightforward with detection limits typically less than 0.05 ng ml^–1 and interference effects are usually minimal. However, both the light REE and Ba form oxide species (typically 1–2% of the parent ion) which can cause significant interference effects if the ratio of these elements to the middle REE, e.g., Eu, and heavy REE is high. A method was developed to avoid spectral interferences on europium from [BaO]⁺, by sensitive measurement of Eu²⁺ ions. Experimental data show that the maximum yield of doubly charged species occurs at a relatively high nebuliser gas flow-rate (0.95 l min^–1) using 1500 W forward r.f. power. Under these optimum operating conditions a stable signal results, with detection limits close to those measured using singly charged ions.