Evaluation of Ethene Addition to the Nebulizer Gas in Inductively Coupled Plasma-Mass Spectrometry for the Removal of Matrix-,Solvent-,and Support-Gas-Derived Polyatomic Ion Interferences

Abstract

Ethene addition to the nebulizer gas is assessed as a means of reducing the levels of polyatomic ions in ICP-MS. It was found that, while the absolute analyte response was generally poorer with the addition of ethene, the levels of the interferences were greatly reduced, when compared to the all argon plasma. The plasma operating conditions, with the addition of ethene to the nebulizer gas, were optimized with the use of a variable-step-size Simplex procedure in order to remove or reduce the ArO⁺, ArCl⁺, ClO+, CeO⁺, ArNa⁺, SO₂⁺/S₂⁺, and PO₂⁺ interferences. Complete removal of the ArCl⁺, ArNa⁺, SO₂⁺/S₂⁺, and PO₂⁺ was achieved, while the levels of the remaining interferences were very much reduced. Detection limits for As, Se, and V in 10% HCl were excellent (0.27, 2.7, and 2.04 ng cm⁻³, respectively), as was the detection limit for Cu in 1% H₃PO₄ at 6.9 ng cm⁻³. Cu, Ni, and Zn detection limits in the presence of H₂SO₄ and sodium ions were also improved, and the detection limit for Fe was 0.48 ng cm⁻³. Levels of CeO⁺ were reduced to just 0.2% relative to Ce. Recovery tests and the analysis of certified reference materials further demonstrated the utility of the optimal conditions. A set of compromise ethene conditions was identified and shown to be of value in reducing the interferences simultaneously.