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

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.