title: Determination and speciation of trace and ultratrace selenium ions by energy-dispersive X-ray fluorescence spectrometry using graphene as solid adsorbent in dispersive micro-solid phase extraction.
abstract: A dispersive micro-solid phase extraction (DMSPE) with graphene as a solid adsorbent and ammonium pyrrolidinedithiocarbamate (APDC) as a chelating agent was proposed for speciation and detemination of inorganic selenium by the energy-dispersive X-ray fluorescence spectrometry (EDXRF). In developed DMSPE, graphene particles are dispersed throughout the analyzed solution, therefore reaction between Se(IV)-APDC complexes and graphene nanoparticles occurs immediately. The concentration of Se(VI) is calculated as the difference between the concentration of selenite after and before prereduction of selenate. A central composite face-centered design with 3 center points was performed in order to optimize conditions and to study the effect of four variables (pH of the sample, concentration of APDC, concentration of Triton-X-100, and sample volume). The best results were obtained when suspension consisting of 200 µg of graphene nanosheets, 1.2 mg of APDC and 0.06 mg of Triton-X-100 was rapidly injected to the 50 mL of the analyzed solution. Under optimized conditions Se ions can be determined with a very good recovery (97.7±5.0% and 99.2±6.6% for Se(IV) and Se(VI), respectively) and precision (RSD=5.1-6.6%). Proposed DMSPE/EDXRF procedure allowed to obtain low detection limits (0.032 ng mL(-1)) and high enrichment factor (1013±15). The proposed methodology was successfully applied for the determination of Se in mineral, tap, lake and sea water samples as well as in biological materials (Lobster Hepatopancreas and Pig Kidney).
authors.affiliation: Institute of Chemistry, University of Silesia, 40-006 Katowice, Szkolna 9, Poland.
authors.forename: Karina
authors.initials: K
authors.lastname: Kocot
authors.affiliation: Department of Pharmacy, Unit of Pharmaceutical and Food Chemistry and Technology, University of Genoa, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Leardi
authors.affiliation: Institute of Chemistry, University of Silesia, 40-006 Katowice, Szkolna 9, Poland.
authors.forename: Beata
authors.initials: B
authors.lastname: Walczak
authors.affiliation: Institute of Chemistry, University of Silesia, 40-006 Katowice, Szkolna 9, Poland. Electronic address: rafal.sitko@us.edu.pl.
authors.forename: Rafal
authors.initials: R
authors.lastname: Sitko
mesh_terms: D000327:Adsorption; D000818:Animals; D033364:Decapoda; D060766:Drinking Water / Q000032:analysis; D006108:Graphite / Q000737:chemistry*; D043143:Hepatopancreas / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007668:Kidney / Q000737:chemistry; D060106:Lakes / Q000737:chemistry; D008900:Mineral Waters / Q000032:analysis; D017830:Octoxynol / Q000737:chemistry; D011759:Pyrrolidines / Q000737:chemistry; D012623:Seawater / Q000032:analysis; D012643:Selenium / Q000032:analysis* / Q000737:chemistry; D052617:Solid Phase Microextraction; D013052:Spectrometry, X-Ray Emission; D013552:Swine; D013859:Thiocarbamates / Q000737:chemistry
chemical_list: D060766:Drinking Water; D008900:Mineral Waters; D011759:Pyrrolidines; D013859:Thiocarbamates; C020972:pyrrolidine dithiocarbamic acid; D006108:Graphite; D017830:Octoxynol; D012643:Selenium
keywords: DMSPE; Environmental samples; Selenium; Speciation; Trace analysis