Ion chromatographic separation of sulfur-containing inorganic anions with an ICP–MS as element-specific detector

Abstract

An inductively coupled plasma mass spectrometer (ICP–MS) was used as element-specific detector for sulfide, sulfite, sulfate, and thiosulfate after their chromatographic separation on a Dionex IonPac ® AS12A analytical column. The sulfur-containing anions were detected as 32S 16O + at m/z=48 with the ICP–MS operated with cool and normal plasma conditions, both tuned for the production of high oxide ratios. Three different mobile phases [(NH 4) 2CO 3, Na 2CO 3, and NaOH] were tested. The ICP–MS signal at m/z=48 for the sulfur-containing anions was obtained only with NaOH based eluents and application of a membrane suppressor for removal of sodium. The detection limits ( S/N=3, calculated on elemental basis) at optimal chromatographic conditions for sulfide, sulfite, sulfate, and thiosulfate were 35 μg l −1, 200 μg l −1, 130 μg l −1, and 270 μg l −1, respectively. A lower detection limit for sulfide was found to be a result of a higher absolute sulfur amount input into the plasma due to the release of the dissolved H 2S from the aerosol droplets into the gas phase. Severe signal suppression for sulfide with cool plasma and shortening of the sulfide retention with normal plasma were observed in the case of highly saline samples. Both effects were confirmed to be caused by chloride anions.