title: Green approach for ultratrace determination of divalent metal ions and arsenic species using total-reflection X-ray fluorescence spectrometry and mercapto-modified graphene oxide nanosheets as a novel adsorbent.
abstract: A new method based on dispersive microsolid phase extraction (DMSPE) and total-reflection X-ray fluorescence spectrometry (TXRF) is proposed for multielemental ultratrace determination of heavy metal ions and arsenic species. In the developed methodology, the crucial issue is a novel adsorbent synthesized by grafting 3-mercaptopropyl trimethoxysilane on a graphene oxide (GO) surface. Mercapto-modified graphene oxide (GO-SH) can be applied in quantitative adsorption of cobalt, nickel, copper, cadmium, and lead ions. Moreover, GO-SH demonstrates selectivity toward arsenite in the presence of arsenate. Due to such features of GO-SH nanosheets as wrinkled structure and excellent dispersibility in water, GO-SH seems to be ideal for fast and simple preconcentration and determination of heavy metal ions using methodology based on DMSPE and TXRF measurement. The suspension of GO-SH was injected into an analyzed water sample; after filtration, the GO-SH nanosheets with adsorbed metal ions were redispersed in a small volume of internal standard solution and deposited onto a quartz reflector. The high enrichment factor of 150 allows obtaining detection limits of 0.11, 0.078, 0.079, 0.064, 0.054, and 0.083 ng mL(-1) for Co(II), Ni(II), Cu(II), As(III), Cd(II), and Pb(II), respectively. Such low detection limits can be obtained using a benchtop TXRF system without cooling media and gas consumption. The method is suitable for the analysis of water, including high salinity samples difficult to analyze using other spectroscopy techniques. Moreover, GO-SH can be applied to the arsenic speciation due to its selectivity toward arsenite.
authors.affiliation: †University of Silesia, Institute of Chemistry, Szkolna 9, 40-006 Katowice, Poland.
authors.forename: Rafal
authors.initials: R
authors.lastname: Sitko
authors.affiliation: †University of Silesia, Institute of Chemistry, Szkolna 9, 40-006 Katowice, Poland.
authors.forename: Paulina
authors.initials: P
authors.lastname: Janik
authors.affiliation: †University of Silesia, Institute of Chemistry, Szkolna 9, 40-006 Katowice, Poland.
authors.forename: Beata
authors.initials: B
authors.lastname: Zawisza
authors.affiliation: ‡University of Silesia, Institute of Physics, Uniwersytecka 4, 40-007 Katowice, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Talik
authors.affiliation: §Department of Chemistry, University of Girona, Campus Montilivi, 17071 Girona, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Margui
authors.affiliation: ∥Laboratory of X-ray Analytical Applications, Institute of Earth Sciences Jaume Almera, CSIC, Solé Sabarís s/n, 08028 Barcelona, Spain.
authors.forename: Ignasi
authors.initials: I
authors.lastname: Queralt