Addition of molecular gases to argon gas flows for the reduction of polyatomic-ion interferences in inductively coupled plasma mass spectrometry

Abstract

Addition of 1% N₂ to the coolant Ar gas flow at a nebulizer gas flow rate of 0.95 dm³ min^–1 can eliminate ⁴⁰Ar³⁵Cl⁺ and dramatically reduce ³⁵Cl¹⁶O⁺ and ³⁷Cl¹⁶O⁺, without losing sensitivity for a representative analyte, In. Addition of 3% N₂ to the central channel gas flow, at a nebulizer gas flow rate of 0.70 dm³ min^–1, has the same effects on polyatomic-ion interferences but also results in a loss in sensitivity to some extent. No significant effects on oxides (⁴⁸Ti¹⁶O⁺, ¹⁴⁰Ce¹⁶O⁺, ²³⁸U¹⁶O⁺) and doubly charged (¹³⁸Ba²⁺) species were observed with or without N₂ addition. Addition of CH₄ to the Ar gas flows has a similar effect to that of N₂ addition, but results in carbon deposition on the sampling cone and a more complicated spectrum. Results of analyte determination for a reference material confirmed that addition of N₂ could be applied to real samples.