Ultrasound-assisted dispersive micro-solid phase extraction using molybdenum disulfide supported on reduced graphene oxi
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ORIGINAL PAPER
Ultrasound-assisted dispersive micro-solid phase extraction using molybdenum disulfide supported on reduced graphene oxide for energy dispersive X-ray fluorescence spectrometric determination of chromium species in water Katarzyna Pytlakowska 1
&
Karina Kocot 1
&
Michał Pilch 2
&
Maciej Zubko 3
Received: 5 November 2019 / Accepted: 4 August 2020 # The Author(s) 2020
Abstract Molybdenum disulfide (MoS2) was supported on graphene oxide (GO) by hydrothermal method. The resulting nanocomposite (MoS2-rGO) was characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The experiments show that at pH 2, MoS2-rGO has a great affinity for adsorption of hexavalent chromium ions while Cr(III) ions remain in aqueous sample. In the adsorption process, the dominant role plays chemisorption. The determined adsorption capacity is 583.5 mg g−1. Parameters affecting the extraction process, namely sample pH, sample volume, contact time, and matrix ions, were investigated by sequential batch tests. Under optimal conditions (pH 2, sample volume 50 mL, sonication time 10 min, adsorbent mass 1 mg), the calibration curve covers the 1–200 ng mL−1 range with a correlation coefficient (R2) of 0.998. The recovery of the method is 97 ± 3%. Other data of merit include a relative standard deviation of < 3.5%, enrichment factor of 3350, and detection limit of 0.050 ng mL−1. The accuracy of the method was confirmed by analysis of the reference materials QC1453 (chromium VI in drinking water) and QC3015 (chromium VI in seawater). The method was successfully applied to chromium speciation in water samples, including high salinity ones. The concentration of Cr(III) was calculated as the difference between the total concentration of chromium (after oxidation of Cr(III) to Cr(VI) with potassium permanganate) and the initial Cr(VI) content. Keywords Preconcentration . Hexavalent chromium determination . Chromium speciation . EDXRF . Environmental samples
Introduction Determination of chromium species in waters is of prime interest due to their contrasting bioavailability and physiological Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-04476-4) contains supplementary material, which is available to authorized users. * Katarzyna Pytlakowska [email protected] 1
Institute of Chemistry, University of Silesia, ul. Szkolna 9, 40-006 Katowice, Poland
2
Institute of Physics, University of Silesia, 75 Pułku Piechoty 1a, 41-500 Chorzów, Poland
3
Institute of Materials Science, University of Silesia, 75 Pułku Piechoty 1a, 41-500 Chorzów, Poland
properties. According to the World Health Organization (WHO) [1] and the United States Environmental Protection Agency (EPA) [2], the permissible level of total chromium content in drinking water is 50 ng mL−1 and 100 ng mL−1, respectively. Most analytical techniques including inductively coupled plasma atomic emission spectrometry (ICP-OES), inductively coupled pl
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