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Separation of mercuric ions using 2-thienylbenzimidazole/cucurbit[7]uril/iron-oxide nanoparticles by pH control
Falguni Chandra, Paltan Laha, Farah Benyettou, Tina Skorjanc, Na'il Saleh, 2023, izvirni znanstveni članek

Opis: 2-Thienylbenzimidazole (TBI)/cucurbit[7]uril (CB7) host–guest complex was used as a motif to significantly improve the turnover of γ-Fe3O4 magnetic nanoparticles for potential application in the separation of toxic mercuric ions in polluted water samples. The mechanism of restoring the original solid materials is based on applying the pH-controlled preferential binding of the CB7 host to the TBI guest. The analytical application of this concept has not been realized in the literature. The pH-controlled stimuli-responsive abilities were confirmed in aqueous solution by the three-order of magnitudes higher stability constant of the protonated TBIH+/CB7 complex (e.g., K = 4.8 × 108 M−1) when compared to neutral TBI/CB7 complex (e.g., K = 2.4 × 105 M−1), also manifested in an increase in pKa values by ~ 3.3 units in the ground state. The supramolecular interaction and adsorption on iron oxide nanoparticles (NPs) were also spectroscopically confirmed in the solid state. The excited-state lifetime values of TBI/CB7NPs increased upon lowering the pH values (e.g., from 0.6 to 1.3 ns) with a concomitant blue shift of ~ 25 nm because of polarity effects. The time-resolved photoluminescent behaviors of the final solids in the presence of CB7 ensured pH-driven reusable systems for capturing toxic mercuric ions. The study offers a unique approach for the controllable separation of mercury ions using an external magnet and in response to pH through preferential binding of the host to guest molecules on the top of magnetic surfaces.
Ključne besede: iron oxide nanoparticles (IONPs), mercury, thienylbenzimidazole, cucurbit[n]uril
Objavljeno v RUNG: 13.07.2023; Ogledov: 315; Prenosov: 0
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Selenium affects mercury ligand environment in terrestrial food chain – a XAS study
Katarina Vogel Mikuš, Alojz Kodre, Iztok Arčon, Anja Kavčič, 2022, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: Selenium (Se) supplied in inorganic form (as selenate or selenite) was shown to decrease mercury (Hg) toxicity by forming HgSe in soils as well as in animal and human tissues, while for plants there is no evidence of Hg-Se complexation. Although Se in not an essential element for plants it was shown to counteract various abiotic stresses when applied at trace amounts. The aim of this work was therefore to study physiological responses and Hg speciation in plant/ fungi-animal food chain. Lettuce (Lactuca sativa) and porcini mushrooms (Boletus edulis) were taken as model plant/ fungal species and Spanish slug (Arion vulgaris) as a model animal species. The plants, fed to the slugs, were grown in HgCl2 contaminated soil or soil from the vicinity of Hg mine in Idrija with traces of HgS and methyl Hg). Physiological parameters of plants and slugs were monitored during the experiment. At the end the biological material was frozen in LN2 and freeze dried. Hg L3-edge (12284 eV) XANES and EXAFS spectra of the biological samples and standards were measured at liquid helium temperature in fluorescence detection mode at the BM30B beamline of the ESRF synchrotron in Grenoble, using the 30-segment germanium solid state detector [1]. The results showed that addition of Se alleviated Hg toxic effects in the food chain started at HgCl2-contaminated soil, while for the soil from Idrija, containing low amounts of highly toxic methyl-Hg, the beneficial effect was less prominent [2]. No Hg-Se complexes were detected in plants, while in mushrooms and slugs the complexation was confirmed. Addition of Se to the plants, however, changed Hg ligand environment in plant tissues from sulphur to nitrogen ligands. Hg and Se both target the -SH functional groups in the plant tissues, so toxic effects of Hg are rather enhanced than alleviated by addition of Se. Nevertheless, the addition of Se to the plants is beneficial for higher trophic levels and lowers Hg toxicity for the primary consumers, the slugs.
Ključne besede: mercury, toxicity, ligand environment, XANES, EXAFS, food chain, plant, slug, fungi
Objavljeno v RUNG: 05.12.2022; Ogledov: 810; Prenosov: 0
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Thioether-crown-rich calix[4]arene porous polymer for highly efficient removal of mercury from water
Dinesh Shetty, Tina Škorjanc, izvirni znanstveni članek

Ključne besede: Mercury, Sulfur, Metals, Adsorption, Polymers
Objavljeno v RUNG: 02.09.2020; Ogledov: 2162; Prenosov: 0
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Leja Goljat, 2019, doktorska disertacija

Opis: Environmental pollution is one of the greatest challenges that the world is facing today. Toxic compounds, such as pesticides, allergens, pharmaceuticals, toxins and heavy metals are widely present in the air, water and soil, and can affect the health of people and animals even in small quantities, as well as they may cause long- or short-term damage in plants [Hill, 1997]. Heavy metals (mercury, arsenic, cadmium…) are widely spread in the environment. They derive from a number of sources, including mining, industrial wastes and vehicle emissions [Tchounwou et al., 2012]. They are easily incorporated into biological molecules and exert their toxic effects by displacing essential metals of a lower binding power in biologically active molecules or by acting as noncompetitive inhibitors of enzymes, affecting neurological, reproductive, renal and hematological systems [Sunil D’Souza et al., 2003; Heavy-Metal Pollution, 2018]. Metals form countless compounds (e.g. metal complexes and organometallic compounds) which are essential for living organisms (vitamin B12, hemoglobin, chlorophyll) and/or have a wide range of applications in industry and other areas, including analytical chemistry. Because of the potential risk which toxic metals represent to the living organisms and also because of the importance of some essential metals, different analytical techniques and detection methods have been developed for studies of their occurrence, fate and concentration in the environment and in organisms. However, providing a required sensitivity for determination and speciation of different metals and their compounds, especially in small- volume samples is still a challenge. Therefore, general objectives of this dissertation were development of novel analytical methods for sensitive, reliable and fast determination of metal species, based on highly sensitive optothermal technique thermal lens spectrometry (TLS), which can be used as detection tool following colorimetric reaction of a selected metal ion or for direct detection of colored organometallic compounds. This dissertation is composed of the following chapters: introduction, research goals, theoretical background, results and discussion, conclusion and references. The core of this dissertation is presented in the fifth chapter (results and discussion), which is divided into three parts. They separately cover development of methods for determination of iron redox species, pyoverdine and Fe-pyoverdine complexes and mercury. Pyoverdine is a siderophore, excreted by a certain bacteria in order to scavenge iron in the environment and is closely related to the chemistry of iron in such biological systems. Therefore, the first two parts are closely related. Procedures for batch mode thermal lens microscopy (TLM), flow-injection thermal lens sprectrometry (FIA-TLS) and µFIA-TLM (flow injection and TLS detection in microspace) were developed for Fe(II) and Fe(III) determination, based on colorimetric reaction of Fe(II) with 1,10-Phenanthroline. All these procedures were focused on cloudwater examination with a tendency to minimize sample consumption but at the same time preserve low limits of detection (LOD) and limits of quantification (LOQ). TLM measurements with highly collimated probe beam were performed in a 100 μm optical path length cell (40 µL volume), which resulted in a considerably smaller sample volume requirement (500 µL in total) and consumption, as compared to UV-Vis spectrophotometry, which required at least 25 mL of sample due to large volume (almost 30 mL) of the 10 cm optical path-length sample cell. LODs for mode-mismatched TLM were 0.16 and 0.14 µM for Fe(II) and Fe(total) (sum of Fe(II) and Fe(III) concentrations), respectively, while LODs for UV-Vis spectrophotometry were 0.01 µM for both Fe(II) and Fe(total). By using the mode mismatched TLM we were able to detect concentrations corresponding to absorbances as low as 1.5 × 10-5, while the lowest absorbance detectable on the UV-Vis spectrophotometer corresponded to 1.1 × 10-3, despite the use of the 10 cm optical path-length cell. Another important step in the development of new methods for Fe(II) and Fe(III) determination was the use of TLS detection in FIA (FIA-TLS). By injecting 50 µL of the sample into the FIA-TLS system, cca. 10 times lower LODs were achieved (1 × 10-3 µM for Fe(II) and 8 × 10-4 µM for Fe(total)), as compared to the UV- Vis spectrophotometry. Nevertheless, the development of μFIA-TLM method, with on-line colorimetric reaction for Fe(II) and Fe(III) determination is considered as the most important achievement of this study. The results show that despite 100 times shorter optical path length and low sample consumption (3 µL of each sample/injection) compared to UV-Vis spectrophotometry, LODs for µFIA-TLM were 0.10 and 0.07 μM for Fe(II) and Fe(total) respectively, which is sufficiently for cloudwater analysis, since concentrations, lower than 0.1 μM are not expected [Parazols et al., 2006; Deguillaume et al., 2014]. Linear range for Fe(II) and Fe(III) determination by μFIA-TLM was between 0.1 and 70 µM. To test the accuracy of this method, artificial cloudwater was prepared, spiked with different amounts of Fe(II) and Fe(III) and analyzed for iron content by µFIA-TLM and UV-Vis spectrophotometry. Good agreement was observed between the two methods. To ascertain the ruggedness of the method 7 (or more) replicate determinations at two different concentrations for both, Fe(II) and Fe(total) in artificial cloudwater were carried out on day 1 (replicates were measured instantly after fortification), day 2 and day 5. A student’s t-test (p=0.05) was applied to compare 3 sets of obtained data (day 1, day 2 and day 5) and showed that sets are not significantly different from each other. Considering very low sample volume requirement of µFIA-TLM, this should be the method of choice for determination of Fe(II) and Fe(III) in investigations of processes in cloudwater, where multiparameter analysis is desired (determination of other ions, ligands, microbial counts, etc.). When larger sample volumes are available, FIA-TLS can be used for accurate determination of iron species at lowest concentration levels. High performance liquid chromatography (HPLC) was applied for separation and detection of pyoverdine (PVD), produced by Pseudomonas fluorescens 36b5, a bacterial strain isolated from the aqueous phase of clouds at the Puy de Dôme station (1465 m, France). Reversed-phase (RP) chromatography (RP-18 chromatographic column Hypersil gold), hydrophilic interaction liquid chromatography (HILIC) (ZIC®-Hilic column) and three different detection systems (diode-array (DAD), spectrofluorimetry (FLD) and TLS) were tested for their performance in separation and determination of pyoverdines and corresponding complexes of pyoverdine with iron (Fe(III)-PVDs). PVDs and Fe(III)-PVD complexes could not be separated and quantified by applying HILIC technique, therefore it was concluded, that HILIC is not suitable for HPLC-DAD and also not for HPLC-TLS, since the method should offer a simultaneous sensitive detection of free PVDs as well as Fe(III)-PVD complexes in a single chromatographic run. Since pyoverdine standards were available only as a mixture of several different forms of PVDs, whereby the exact composition was unknown, the quantification of each of the four major specie (two fluorescent PVDs and two nonfluorescent Fe(III)-PVDs) in the standard, which was obtained from Université Clermont Auvergne, Institut de Chimie de Clermont-Ferrand, was performed. When applying Hypersil gold column, a linear correlation between fluorescence intensity and absorbance of each component was observed in a concentration range 3–24 µg/mL, whereby LODs were estimated to be 0.03–0.04 µg/mL for each of the major PVD species (HPLC-DAD). Even though HPLC-FLD method provided cca. 100 times lower LODs, it is not the method of choice for determination of PVD species in cloudwater, because it does not allow detection of PVD complexes with Fe(III). When comparing HPLC-TLS and HPLC-DAD, LODs were 5 to 8 times lower in case of HPLC-TLS, which was a significant improvement. Furthermore, recoveries (89–111 %) at two concentration levels of four PVD species in two independent samples, showed good reliability of the method. Almost all mercury in uncontaminated drinking-water is thought to be in the form of Hg2+ [WHO, 2010]. Therefore, the method for Hg2+determination based on colorimetric reaction with triamterene, described originally by Al-Kady and Abdelmonem was further investigated in this study, as well as the possibilities of application of this reaction for Hg2+ determination by TLS. The stoichiometry of the complex formation was determined by the method of continuous variations and saturation experiment, suggesting formation of the complex with the formula Hg2-triamterene. The obtained value of the molar absorption coefficient was 9988 Lmol-1cm-1 at 403 nm, which significantly contradicts the existing data in literature, which reports the molar absorption coefficient of 5.32 × 104 Lmol-1cm-1 [Al-Kady and Abdelmonem, 2013]. Even though the spectrophotometric results were not encouraging for triamterene as colorimetric reagent for Hg2+ determination, it was further investigated for its performance in TLS system. Fe(II)-1,10-phenanthroline (ferroin) was used for comparison, because it was well studied for TLS applications previously. The results showed that Hg2-triamterene in solutions was degraded when it was exposed to the light of the excitation beam. Due to the lower molar absorptivity than reported in literature, fotodegradation and unfavorable complex stoichiometry, triamterene was not confirmed as a suitable colorimetric reagent for highly sensitive Hg2+ determination by TLS. In summary, this dissertation investigates alternative approaches for analysis of metal complexes and organometallic compounds in small-volume environmental water samples. Methods, which were developed in this research, could potentially serve as improvements of existing technologies, to facilitate analysis of such samples, by offering simple handling of samples and superior sensitivity over the UV-Vis spectrophotometry.
Ključne besede: thermal lens spectrometry, thermal lens microscopy, high performance liquid chromatography, microfluidics, metal complexes, organometallic compounds, iron, pyoverdine, mercury
Objavljeno v RUNG: 05.09.2019; Ogledov: 3570; Prenosov: 152
.pdf Celotno besedilo (3,65 MB)

Ionomic and metabolomic changes in mercury and selenium exposed plants and animals by X - ray and FTIR spectrometry
Anja Kavčič, Petra Gregorič, Jože Grdadolnik, Iztok Arčon, Katarina Vogel-Mikuš, 2018, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: mercury, selenium, plants, animals
Objavljeno v RUNG: 12.09.2018; Ogledov: 3388; Prenosov: 0
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The Topic of Mining in Secondary School Literature Textbooks from 1850 to 1950
Zoran Božič, 2018, izvirni znanstveni članek

Opis: During the first century of secondary school literature textbook publishing (from the introduction of Slovenian language as a school subject after the March Revolution in the Austrian Empire to the first Five-Year Plan after World War II) over a hundred texts featuring the topic of mining and related activities were included. The first writings have a clearly affirmative attitude towards mining, perceived and presented as a way of promoting general prosperity. The first mentions of the negative aspects of mining and the deceptive folly of coveting precious mineral resources appear towards the end of the 19th century. Only during the interwar period, however, were there various texts which presented mining as an inhumane and dangerous activity. After World War II the approach was again optimistic: in central literature textbooks mining was depicted as the glorification of socialist progress. Relevant texts were published in eight series of textbooks, the first as early as in the Bleiweis series for lower secondary schools in 1850 and the last in the ethnic Slovenian Beličič series of textbooks in 1947. The discovery of mercury in the Idrija mine was described by Valvazor, Kastelic, Hrovat and Oblak.
Ključne besede: natural science, didactics, mineral resources, Idrija mine, mercury
Objavljeno v RUNG: 30.08.2018; Ogledov: 3467; Prenosov: 158
.pdf Celotno besedilo (361,27 KB)

Comparison of Colorimetric Reagents and Their Applicability in Thermal Lens Spectrometry
Leja Goljat, Mikhail A. Proskurnin, Mladen Franko, 2017, objavljeni povzetek znanstvenega prispevka na konferenci

Ključne besede: thermal lens spectrometry, colorimetric reagents, mercury
Objavljeno v RUNG: 30.08.2017; Ogledov: 3887; Prenosov: 0
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