title: Fast and accurate procedure for the determination of Cr(VI) in solid samples by isotope dilution mass spectrometry.
abstract: We present here a new environmental measurement method for the rapid extraction and accurate quantification of Cr(VI) in solid samples. The quantitative extraction of Cr(VI) is achieved in 10 minutes by means of focused microwave assisted extraction using 50 mmol/L Ethylendiamintetraacetic acid (EDTA) at pH 10 as extractant. In addition, it enables the separation of Cr species by anion exchange chromatography using a mobile phase which is a 1:10 dilution of the extracting solution. Thus, neutralization or acidification steps which are prone to cause interconversion of Cr species are not needed. Another benefit of using EDTA is that it allows to measure Cr(III)-EDTA complex and Cr(VI) simultaneously in an alkaline extraction solution. The application of a 10 minutes focused microwave assisted extraction (5 min at 90 °C plus 5 min at 110 °C) has been shown to quantitatively extract all forms of hexavalent chromium from the standard reference materials (SRM) candidate NIST 2700 and NIST 2701. A double spike isotope dilution mass spectrometry (IDMS) procedure was employed to study chromium interconversion reactions. It was observed that the formation of a Cr(III)-EDTA complex avoided Cr(III) oxidation for these two reference materials. Thus, the use of a double spiking strategy for quantification is not required and a single spike IDMS procedure using isotopically enriched Cr(VI) provided accurate results.
authors.affiliation: Faculty of Chemistry, Department of Physical and Analytical Chemistry, University of Oviedo, Julián Clavería 8, 33006 Oviedo, Spain.
authors.forename: Neus
authors.initials: N
authors.lastname: Fabregat-Cabello
authors.forename: Pablo
authors.initials: P
authors.lastname: Rodríguez-González
authors.forename: Ángel
authors.initials: Á
authors.lastname: Castillo
authors.forename: Julien
authors.initials: J
authors.lastname: Malherbe
authors.forename: Antoni F
authors.initials: AF
authors.lastname: Roig-Navarro
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Long
authors.forename: J Ignacio
authors.initials: JI
authors.lastname: García Alonso
mesh_terms: D002852:Chromatography, Ion Exchange / Q000379:methods*; D002857:Chromium / Q000032:analysis* / Q000737:chemistry; D004492:Edetic Acid / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods*; D013058:Mass Spectrometry / Q000379:methods*; D008872:Microwaves; D010084:Oxidation-Reduction; D013997:Time Factors
chemical_list: D002857:Chromium; C074702:chromium hexavalent ion; D004492:Edetic Acid