Abstract

The coupling of ICP-MS with ion chromatography after conductivity suppression has been performed and compared with conductivity detection for the determination of several inorganic anions (IO₃⁻, Cl⁻, ClO₃⁻, BrO₃⁻, Br⁻, HPO₄²⁻, SO₄²⁻) in water samples. The elimination of the sodium ions from the eluent in the suppressor column allowed direct ICP-MS detection using 15 mM Na₂CO₃–7 mM NaHCO₃ as eluent without clogging problems in the nebuliser or sampling cone. Additionally, the use of both conductivity and ICP-MS detection allowed the on-line identification of the anions previously detected by conductivity. Analytical performance characteristics of both detection systems were evaluated showing that SO₄²⁻, Cl⁻ and ClO₃⁻ are better detected by conductivity while BrO₃⁻, Br⁻ and IO₃⁻ are better detected by ICP-MS. Only HPO₄²⁻ showed similar detection limits for both systems. Using a 500 µl sample loop and ICP-MS the detection limit for BrO₃⁻ was 1 ng ml⁻¹, which is well below the required detection limit for this anion. The method was applied to the determination of inorganic anions in different water samples with satisfactory results.