Comparison of interface cones for analysis of sodium-rich samples using quadrupole ICP-MS

This study compares analytical figures of merit such as sensitivity, background, % ¹⁴⁰Ce¹⁶O⁺/¹⁴⁰Ce⁺, ⁴⁰Ar¹⁶O⁺, time dependent and matrix induced interference effects for solutions containing up to 500 mg L⁻¹ Na for a conventional sampler cone designated as the High Performance Interface (HPI) with that obtained with a so-called Xi cone. HPI counts were higher than those observed using the Xi cone by factors of about 10 at low mass, the difference decreasing with increasing mass, and at high mass they were approximately equal to those observed with the Xi cone. As a consequence of low sensitivity when using the Xi interface, there is potential for determining high concentrations of low mass elements. The 4-times lower ⁴⁰Ar¹⁶O⁺ signals and up to two times lower % ¹⁴⁰Ce¹⁶O⁺ of the Xi cone are important analytical figures of merit for minimizing polyatomic ion interferences.

% ¹⁴⁰Ce¹⁶O⁺/¹⁴⁰Ce⁺ varied considerably with depth of sampling and were much higher in the HPI cone than in the Xi cone at large depths of sampling. Na-induced variations were mass dependent and larger in the Xi cone than in the HPI cone, amounting to about 25 and 60%, respectively. Long-term variations for 250 min amounted to about 10 and 25%, respectively. It is concluded that the HPI cone when coupled to a robust ICP (power > 1.3 kW, nebulizer gas flow rate < 0.85 L min⁻¹) is more suited for routine analysis of environmental samples. However, in cases where oxide ion interferences must be reduced and high concentrations of low mass analytes are to be determined, the Xi cone has advantages.