title: A simple and reliable anion-exchange resin method for sulfate extraction and purification suitable for multiple O- and S-isotope measurements.
abstract: BACKGROUND
  The O- and S-isotope compositions of sulfates can be used as key tracers of the fate and sink of sulfate in both terrestrial and extra-terrestrial environments. However, their application remains limited in those geological systems where sulfate occurs in low concentrations. Here we present a simple and reliable method to extract, purify and concentrate sulfate from natural samples. The method allows us to take into account the separation of nitrate, which is known to be an issue in O-isotope analysis.
  
  
  METHODS
  The separation and concentration of sulfate from other anions in any aqueous solution are performed within a few hours via anion-exchange resin. The possible O- (δ18O and Δ17O) and S- (δ34S, Δ33S and Δ36S) isotope exchanges, fractionations and/or contaminations are for the first time monitored during the whole procedure using initial O- and S-mass-dependent and mass-independent sulfate solutions.
  
  
  RESULTS
  After elution in HCl, pure sulfate is fully retrieved and precipitated into BaSO4, which is suitable for O- and S-isotopic measurements using established techniques. The analysis of retrieved barite presents no variation within 2σ uncertainties: ±0.5‰ and ±0.1‰ in O- (δ18O, Δ17O) and ±0.2‰, ±0.02‰ and ±0.09‰ in S- (δ34S, Δ33S and Δ36S) isotope ratios, respectively.
  
  
  CONCLUSIONS
  This study shows that the resin method for sulfate extraction and purification, in addition to being cheap, simple and quick, is applicable for the measurements of all O- and S-isotopic ratios in sulfates (including the Δ17O, Δ33S and Δ36S values). Therefore, this method can be easily used for a high range of natural samples in which sulfate occurs in low concentration including aerosols, ice cores, sediments, volcanic deposits, (paleo)soils and rainwater, and thus it can be a key to our understanding of the sulfur cycle on Earth. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Institut des Sciences de la Terre de Paris (ISTeP), 4 Place Jussieu, 75005, Paris, France.|Sorbonne Universités, UPMC Université Paris 06, Université Versailles St.-Quentin, CNRS/INSU, LATMOS-IPSL, Paris, France.
authors.forename: Erwann
authors.initials: E
authors.lastname: Le Gendre
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Institut des Sciences de la Terre de Paris (ISTeP), 4 Place Jussieu, 75005, Paris, France.
authors.forename: Erwan
authors.initials: E
authors.lastname: Martin
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Institut des Sciences de la Terre de Paris (ISTeP), 4 Place Jussieu, 75005, Paris, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Villemant
authors.affiliation: Laboratoire de Géochimie des Isotopes Stables, Institut de Physique du Globe de Paris, Université Paris Diderot, CNRS UMR 7154, Sorbonne Paris-Cité, 1 rue de Jussieu, 75005, Paris, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Cartigny
authors.affiliation: Laboratoire de Géochimie des Isotopes Stables, Institut de Physique du Globe de Paris, Université Paris Diderot, CNRS UMR 7154, Sorbonne Paris-Cité, 1 rue de Jussieu, 75005, Paris, France.
authors.forename: Nelly
authors.initials: N
authors.lastname: Assayag