Nanokompozyty węglowe w zatężaniu i oznaczaniu wybranych pierwiastków śladowych

Drinking and natural environmental waters contain trace amount of metal ions. On the one hand, metal ions are necessary in order to regulate biological system of living organisms. On the other hand, some metal ions have harmful, toxic and carcinogenic effect. Scientific literature have proposed to use solid sorbents in order to preconcentration/separation of trace amount of metal ions from environmental waters. Most of them show adsorption properties towards cationic species of elements, and only few towards anionic species. The aim of the dissertation is synthesis of new carbon nanocomposites based on graphene (G) and graphene oxide (GO) decorated with cerium (IV) oxide nanoparticles (G/CeO₂ and GO/CeO₂) and aluminium oxide nanoparticles (Al₂O₃/nano-G and Al₂O₃/GO). The synthesized carbon nanocomposites are characterized by good adsorption properties towards cationic as well as anionic species of selected elements. Obtained nanocomposites were investigated by spectroscopic and microscopic techniques, which confirmed that the structure of nanocomposites and the surfaces of G and GO were covered by CeO₂ and Al₂O₃ nanoparticles. The pH conditions of adsorption of selected metal ions on synthesized nanocomposites were investigated. The maximum adsorption capacities of carbon nanocomposites were calculated using Langmuir isotherms and they were in the range 8.4 – 119.4 mg g-1 for G/CeO₂, 5.8 – 30.0 mg g-1 for GO/CeO₂, 32.8 mg g-1 for Al₂O₃/nano-G and 43.9 – 53.9 mg g-1 for Al₂O₃/GO. Adsorption of selected metal ions on nanocomposites were studied for simultaneously influence contact times and sample volumes, influence of coexisting ions and humic acid (HA) the analyte recoveries. Each of obtained carbon nanocomposites was used to develop a new analytical procedures. Dispersive micro solid phase extraction (DMSPE) with nanocomposites as solid sorbents in preconcentration and determination of metal ions in water samples was developed. Preconcentrated analytes were directly determination by energy dispersive X-ray fluorescence spectrometry (EDXRF) without elution step. DMSPE/EDXRF procedure eliminates sources of errors related to possible analytes losses and sample contamination, as well as the principles of Green Analytical Chemistry are regulated. In order to obtained a good results for determination of chromium ions, analyte preconcentrated onto G/CeO₂ and GO/CeO₂ was eluted and determined by inductively coupled plasma - optical emission spectrometry (ICP-OES). In this case EDXRF analysis was impossible due to the spectral coincidences between Cr Kα (5.41 keV) and Ce Lα (4.84 keV), Ce Lβ (5.26 keV) observed in EDXRF spectra. Developed analytical procedures were validated. The following parameters were determined: linearity, limit of detection (LOD), limit of quantification (LOQ), precision and accuracy. Selective adsorption of nanocomposite towards Se(IV) in presence of Se(VI), As(V) in presence of As(III) and Cr(III) in presence of Cr(VI) allowed to carry on speciation analysis as well as determination of selected metal species

Alumina/nano-graphite composite as a new nanosorbent for the selective adsorption, preconcentration, and determination of chromium in water samples by EDXRF

Obtaining new nanocomposites with sorption properties towards chromium is highly important not only from the environmental point of view but also for developing eco-friendly methods of chromium determination. The potential use of aluminum oxidecoated nano-graphite (Al2O3/nano-G) as a new nanosorbent in ultrasound-assisted dispersive micro-solid-phase extraction (DMSPE) for rapid speciation of trace chromium(III) and chromium(VI) ions in natural water was evaluated. In the developed method, the crucial issue is the new nanocomposite synthesized by coating alumina on a nano-graphite surface with sorption properties. Structural researches of the nanocomposite were carried out by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and Raman spectroscopy. Maximum adsorption capacity of Al2O3/nano-G towards Cr(III) was 32.8 mg g−1. The influence of the method’s factors like pH, sample volumes, contact time, coexisting ions, and humic acid on the recovery of chromium was examined. The nanocomposites have been found to be stable and effective as a sorbent in water with high concentrations of selected cations and anions present in water as well as in water of various pH. Al2O3/nano-G is selective for Cr(III) in presence of Cr(VI). Cr(III) was determined by the developed method, total Cr after reduction of Cr(VI) to Cr(III), and Cr(VI) was calculated as the difference between total Cr and Cr(III). After sorption, the nanocomposite with chromium was collected on 5-mm diameter filters and analyzed by energy-dispersive X-ray fluorescence spectrometry (EDXRF) to determine the chromium concentration. The method was characterized by correlation coefficient 0.999, limit of detection (LOD) 0.04 ng mL−1, and relative standard deviation (RSD) 3.5%. Al2O3/nano-G combined with proposed DMSPE/EDXRF was verified by analysis of certificate reference material of natural water (NIST 1640a)

Practical recommendations for feeding the patients with type 2 diabetes and obesity

Zasady żywienia w cukrzycy i otyłości uległy znacznej ewolucji w ciągu ostatnich 10-leci. W niniejszym opracowaniu przedstawiono aktualne zalecenia dietetyczne dla chorych z cukrzycą typu 2 i otyłością, a także praktyczne wskazówki, które można przekazać chorym już podczas pierwszej wizyty. (Forum Zaburzeń Metabolicznych 2011, tom 2, nr 4, 222–230)Principles of nutrition in diabetes and obesity has been a considerable evolution in recent decades. This document presents the current dietary recommendations for patients with type 2 diabetes and obesity, as well as practical tips that you can share with the patient during the first visit. (Forum Zaburzen Metabolicznych 2011; vol. 2, no 4, 222–230

Ceria nanoparticles deposited on graphene nanosheets for adsorption of copper(II) and lead(II) ions and of anionic species of arsenic and selenium

A nanocomposite prepared from graphene nanosheets and cerium nanoparticles (G/CeO2) was applied to the extraction of Se(IV), As(V), As(III), Cu(II) and Pb(II). The structure of G/CeO2 was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The optimal pH values for extraction are 4.0 for As(V), 3.0 for Se(IV), and 6.0 for both Cu(II) and Pb(II). The maximum adsorption capacity of G/CeO2 (expressed as mg·g−1) were calculated by the Langmuir model and are found to be 8.4 for As(V), 14.1 for Se(IV), 50.0 for Cu(II) and 75.6 for Pb(II). The sorbent was applied to dispersive solid phase microextraction prior to direct quantitation by energy-dispersive X-ray fluorescence spectrometry without the need for prior elution. The limits of detection (in ng·mL−1 units) are 0.10 for As(V), 0.11 for Se(IV), 0.19 for Cu(II) and 0.21 for Pb(II). The precisions (RSDs) are <4.5%. The accuracy of the method (1 - 4%) was verified by analysis of the certified reference material (CRM 1640a - natural water). The method was successfully applied in ultratrace element determination and to the speciation of selenium in environmental waters

Preconcentration of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II) with ethylenediamine-modified graphene oxide

We describe a novel solid phase sorbent that was synthesized by coupling graphene oxide (GO) to ethylenediamine (EDA). This nanomaterial (referred to as GO-EDA) is capable of adsorbing the ions of iron, cobalt, nickel, copper, zinc and lead. The ethylenediamine-modified graphene oxide was characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and Fourier transform infrared spectroscopy. The analytical procedure relies on (a) sorption of metal ions on GO-EDA dispersed in aqueous samples; (b) filtering, and (c) direct submission of the filter paper to energy-dispersive X-ray fluorescence spectrometry. This kind of dispersive micro-solid phase extraction was optimized with respect to pH values, concentration of GO-EDA, contact time, and the effects of interfering ions and humic acid on recovery of determined elements. Under optimized conditions, the recoveries of spiked samples range from 90 to 98 %. The detection limits are 0.07, 0.10, 0.07, 0.08, 0.06 and 0.10 ng mL−1 for Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The method has a relative standard deviation of <6 %, and its accuracy was verified by analysis of two standard reference materials [LGC6016 (estuarine water) and BCR-610 (groundwater)]. It was successfully applied to the determination of trace amounts of these metal ions in water samples

Graphene Oxide Decorated with Cerium(IV) Oxide in Determination of Ultratrace Metal Ions and Speciation of Selenium

Graphene oxide decorated with cerium­(IV) oxide (GO/CeO₂) was synthesized and applied in adsorption of several metal ions such as As­(III), As­(V), Se­(IV), Cu­(II), and Pb­(II) from aqueous samples. The important feature of GO/CeO₂ nanocomposite is also its selectivity toward selenite in the presence of selenate. The structure of GO/CeO₂ has been proven by microscopic and spectroscopic techniques. The maximum adsorption capacities of GO/CeO₂ calculated by Langmuir model toward arsenic, selenium, copper, and lead ions are between 6 and 30 mg g^–1. An interesting feature of this adsorbent is its excellent dispersibility in water. Thus, GO/CeO₂ nanocomposite is ideal for fast and simple determination of heavy metal ions using dispersive microsolid phase extraction (DMSPE). Moreover, coupling DMSPE with energy-dispersive X-ray fluorescence spectrometry (EDXRF) is extremely beneficial because it allows direct analysis of adsorbent. Thus, the analyte elution step, as needed in many analytical techniques, was obviated. The influence of sample volume and the sorption time as well as the influence of foreign ions and humic acid on the recovery of determined elements are discussed in the paper. The results showed that developed methodology provided low limits of detection (0.07–0.17 μg/L) and good precision (RSD < 4%). The GO/CeO₂ nanocomposite was applied to analysis of real water samples and certified reference materials (CRM) groundwater (BCR-610) and pig kidney (ERM-BB186)