Application of capillary ion chromatography and capillary ion chromatography coupled with mass spectrometry to determine methanesulfonate and inorganic anions in microliter sample volumes of Antarctic snow and ice

Abstract

The high costs associated with logistics and the collection of Antarctic ice-cores demands scientists to extract the absolute maximum data from these precious resources. Typically, the chemical analyses of these valuable ice cores, and/or of ice cores from low snow accumulation sites, requires the ice samples to be as small as possible. Despite having a relatively long history within the research lab, recently, capillary ion chromatography (Cap-IC) has become a commercial reality allowing its use as a new analytical capability for the determination of inorganic and organic ions based upon reduced sample volumes. A quantitative study on the simultaneous determination of organic and inorganic anions, including fluoride, methanesulfonate, chloride, sulfate and nitrate anions in Antarctic ice and snow samples was carried out. The new Cap-IC method necessitated only 40 μL of injection volume to attain the analytical performances required, compared to the usual 1–5 mL. In this work, the Cap-IC was also coupled with mass spectrometry, and optimised for the identification and quantification of methanesulfonate. The limit of detection for methanesulfonate was decreased to 0.07 μg L⁻¹ using a hyphenated technique, being the lowest detection limit reported until now in the literature for any ion chromatography based method. To validate the new analytical methods, a comparative study was performed with statistical evaluation of the anion concentrations obtained for snow pit samples from the Aurora Basin North, East Antarctica site, by three separate ion chromatography based methods, namely, standard ion chromatography, and Cap-IC coupled to either suppressed conductivity or mass spectrometry detection.