Elimination of chloride interference on arsenic speciation in ion chromatography inductively coupled mass spectrometry using an octopole collision/reaction system

Anion-exchange chromatography with inductively coupled plasma mass spectrometry (ICP-MS) is often used for the speciation of arsenic (As). In this work, either He or H₂ was introduced to the octopole collision/reaction cell to eliminate chloride (Cl⁻) interferences during As speciation by ICP-MS. Polyatomic species, ⁴⁰Ar³⁵Cl and ³⁸Ar³⁷Cl, which are formed in high chloride matrices interfere with the ICP-MS detection of ⁷⁵As. These interferences were reduced or eliminated by introducing He or H₂ to the collision/reaction cell, with some loss in sensitivity when compared to the standard mode (no gas). For example, the sensitivity of As(V) was 30.4 and 17.7% of that observed in standard mode when introducing He and H₂, respectively. Chloride interference was completely eliminated using a flow rate of 3.0 mL min^− 1 with H₂ as a reaction gas with detection limits in the range of 0.3-0.6 μg L^− 1. The developed method was applied to determination of arsenic species in waters containing high concentrations of chloride by following a simple procedure and without modification of the ICP-MS instrument.