Voltammetric determination of lutetium

Half wave potential of lutetium was determined by anodic stripping voltammetry using various electrolyte solutions at the mercury electrode. The influence of electrolyte pH on the value of peak current was also observed. The results show that the choice of the supporting electrolyte and the electrolyte pH strongly influence the voltammetric behaviour of lutetium.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Evaluation of sealing ability of chemically softened gutta-percha technique

Introduction. Obturation of the root canal is the final phase of endodontic therapy and it is usually used to assess the quality of endodontic treatment. The objective of this study was to examine the quality of apical sealing of the root canal after application of chemically softened gutta-percha. Material and Methods. Thirty extracted single rooted and multi rooted teeth, divided into two groups according to the material for obturation, were used in the study. After root canal instrumentation using step-back technique, obturation was completed using chemically softened gutta-percha and AH Plus and Apexit paste. The effect of apical sealing was assessed regarding the type of material used for the obturation. After obturation, teeth were coated with two coats of varnish and immersed in 50% solution of silver nitrate for twelve hours, and then longitudinally cut using diamond disc. Linear dye penetration was observed using light microscope and twenty five times magnification. The apical leakage was calculated using the measuring scale, previously mounted on microscope lens. Results. The results showed that the average penetration of silver nitrate in single rooted teeth obturated with the AH Plus paste was 132.8 μm, while in teeth obturated with Apexit, it was 148.6 μm. The difference was not statistically significant. Apical leakage in multi rooted teeth obturated with softened gutta-percha and AH Plus paste was 117.3 μm while in teeth obturated with Apexit, it was 158.5 μm. The difference was statistically significant. Conclusion. The lowest dye penetration in the apical portion of the canal was observed in multi rooted teeth obturated with AH Plus paste and the highest penetration of silver nitrate was in multi rooted teeth obturated with Apexit paste

Determination of copper and nickel by ion chromatography and voltammetry

Simultaneous determination of copper(II) and nickel(II) by ion chromatography (IC) has been optimized and the detection limits of the new method were compared to stripping voltammetry. The best eluent enabling fast end efficient separation of Cu(II) and Ni(II) is a mixture of 8 mM citric and 0.3 mM oxalic acid using a Metrosep C2 (Metrohm) IC column. The detection limits are significantly lower using stripping voltammetry, while IC is considerably faster.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Spatial distribution of multielements including lanthanides in sediments of Iron Gate I Reservoir in the Danube River

Recent studies show that lanthanides (Ln) are becoming emerging pollutants due to their wide application in new technologies,but their environmental fate, transport, and possible accumulation are still relatively unknown. This study aims to determinemajor and trace elements including Ln in the Danube River sediment which either belong or close to the Iron Gate Reservoir. TheIron Gate Reservoir is characterized by accumulation of sediments as an effect of building hydropower dam Iron Gate I. Thesurface sediments were collected on the Danube River—1141 to 864 km and three tributaries along this waterway. Two samplesof deep sediments were used for comparison. The results indicate the significant upward enrichment of Zn, Sb, Cr, Nd, and Dy insediments belongs to the Iron Gate Reservoir. The sample 4-Smed is labelled as a hot spot of contamination with Zn, Cr, As, Sb,Nd, and Dy. Also, a trend of increasing concentration in the time period from 1995 to 2016 was found for elements Zn, Cr, and Niin sediment samples in the Iron Gate Reservoir. Chemometric analysis shows the grouping of sample sites into clusters charac-terized by the following properties: (i) increased concentration of all measured elements (samples within the Iron Gate Reservoir);(ii) increased Cu concentration (11-Pek); and (iii) lower concentrations of the measured elements (deep sediments). The datapresented hereby contribute to the monitoring of pollution of the River Danube sediments and give the first view of Ln profile inthe studied sediments

Vortex-assisted ionic liquid based liquid-liquid microextraction of selected pesticides from a manufacturing wastewater sample

The ionic liquid based vortex-assisted liquid-liquid microextraction (IL-VALLME) procedure was developed and validated for determination of four pesticides in a manufacturing wastewater sample: acetamiprid, imidacloprid, linuron and tebufenozide. The following ILs were tested as extractants: 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium hexafluorophosphate, and 1-methyl-3-octylimidazolium hexafluorophosphate. The extraction efficiency and the enrichment factor dependencies on the type and amount of ionic liquids, extraction and centrifugation time, volume, pH and the ionic strength of the sample, were investigated. The concentration of pesticides in the aqueous and IL phases was determined by HPLC-DAD. The optimal conditions for extraction of the pesticides were determined: the aqueous sample volume of 10 mL with the addition of 0.58 g NaCl, 40 A mu L of the 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide as extractant, 2 min extraction under vigorous mixing applying the vortex agitator, and separation of the phases by centrifugation for 2 min at 1000 rpm. The calibration curves of the pesticides showed good linear relationship (r(2) a parts per thousand yen 0.9996) in the concentration range from 0.005 to 1.00 mg L-1. Determined LOD values are 1.8, 2.3, 4.8 and 8.6 A mu g L-1 for Tebf, Linr, Acet and Imid, respectively. The optimized IL-VALLME was applied for determination of the pesticides in the pesticide manufacturing wastewater

Phase diagram ofthe selected aqueous twophase systems based on ionic liquids

Liquid-liquid equilibrium data have been reported for aqueous two-phase systems formed by imidazolium-based ionic liquids, 1-hexyl-3-methylimidazolium chloride, and 1-butyl-3-methylimidazolium dicyanamide, with inorganic salts,K2HPO4 and K3PO4. The binodal curves were fitted to a three parameter equation and the tie line length was calculated.PHYSICAL CHEMISTRY 2014: 12th International Conference on Fundamental and Applied Aspects of Physical Chemistry;Belgrade (Serbia),22-26 September, 201

The possibility of using polymer-based phase change materials for thermal energy storage

Phase change materials (PCM) are attractive energy storage technologies due to their high energy storage density and the ability to reversible absorb and release thermal energy at a nearly constant temperature. Polymers and polymer-based eutectic mixtures are promising PCMs. This study aims to investigate heat properties (melting temperature (Tm), latent heat (ΔH) and thermal conductivity(λ)) of potential PCMs based on polyethylene glycol polymer (PEG2000). We prepared following two and three components materials: PEG2000: ethylene glycol (5:6): PEG2000: PPG 400 (1:5); PEG2000: PPG400: Choline chloride (2:2:15); PEG2000: ethylene glycol (5:6); PEG2000: Glyoxal (5:2). The prepared three components material belong to deep eutectic solvents. Tm of the prepared materials are lower compared to pure PEG2000 (Tm = 57 ºC) e.g. Tm of PEG2000: PPG400: Choline chloride is 43 ºC. The determined melting enthalpies are also lower for prepared materials compared to PEG2000. This decrease is lower for eutectic mixture such as PEG2000: Choline chloride: ethylene glycol. We can conclude based on the obtained result that eutectic mixtures based on polymers are promising PCMs.XII Međunarodna konferencija o društvenom i tehnološkom razvoju, Trebinje, 15-18. juni 2023

Aqueous biphasic systems comprising copolymers and cholinium-based salts or ionic liquids: insights on the mechanisms responsible for their creation

Aqueous biphasic systems (ABS) formed by copolymers and ionic liquids (ILs) have demonstrated to be effective separation platforms, but there is still a gap on the complete understanding of the molecular-level mechanisms ruling the two-phase formation for this type of systems. This work addresses the determination of the liquid-liquid equilibrium of ABS composed of cholinium-based salts or cholinium-based ILs and the triblock copolymer Pluronic PE6200 (PL6200). It is demonstrated that PL6200 can form ABS with all investigated cholinium-based salts or ILs, contrarily to most poly(ethylene)glycol polymers, which is due to the presence of hydrophobic propylene oxide (PO) blocks. From the phase diagrams behavior and IL/salt anions properties, it is shown that the formation of ABS with cholinium-based salts is ruled by the anions polar surface and ability to be hydrated, whereas in systems comprising ILs van der Waals interactions between the copolymer and the IL cannot be discarded. The partition of a series of alkaloids in these systems, namely caffeine, nicotine, theophylline, and theobromine, was additionally appraised. It is shown that caffeine, theophylline, and theobromine preferentially migrate to the more hydrophobic PL6200-rich phase, and that their partition depends on the water content in the respective phase, being ruled by the phases’ hydrophobicity. On the other hand, nicotine, with the most prominent hydrophobic character amongst the studied alkaloids, preferentially migrates to the salt- or IL-rich phase, in which interactions occurring between this alkaloid and the IL/salt cannot be discarded. The ABS formed by cholinium dihydrogenphosphate is the most selective system identified to separate nicotine from the remaining alkaloids, giving some insights into their investigation as separation platforms for alkaloids from natural extracts.publishe

Instrumental neutron activation for analysis of spatial distribution of heavy metals in surface sediments of the Danube River

In this paper, the spatial distribution of the heavy metals including technology-critical elements (TCE) in the surface river sediments was investigated. The surface sediments of the Danube River in the Republic of Serbia, as well as three tributaries were analysed. Instrumental neutron activation analysis (INNA) has been applied for quantification of the selected element in the samples. The main featues of INAA are: simultaneously determining more than 40 elements with high sensitivity and low detection limit, high selectivity due to specific nuclear reaction for each element, the nondestructive method, the sample stays intact and no chemical separation treatment is involved, simple sample preparation step, especially solid samples, a small quantity of sample (≈ 200 μg) and determination of the total element concentration independent of chemical species, real total analysis since the test portion does not have to be dissolved. The heavy metal concentration in the sediments connected with hydropower dam and accumulation of sediments in the reservoir systems Iron gate I and Iron gate II were discussed. Surface river sediments were collected from the river bottom at the central and the deepest part using an Ekman grab sampler and air-dried in a thin layer in the dark at room temperature (23 ± 1 °C). Also, deep river sediments (1.5 and 7 m) were collected and used for comparison purpose. After drying, the samples were homogenized using a pestle and mortar and sieved through a 1-mm sieve to ensure sample homogeneity. INAA were used to quantify following elements: Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ga, As, Se, Yr, Ag, Cd, Sb, La, Ce. Nd, Sm, Eu, Gd, Tb, Dy, Tm, Yb, Th, Hf, Ta, W, Au, Hg and U. Irradiations were performed at the pulsed reactor IBR 2 (Frank Laboratory of Neutron Physics, JINR, Dubna, Russian Federation) using epithermal neutrons. Principal Component Analysis (PCA) and Power transformation as a pretreatment method were applied for analysis of experimental data. It was found that the increase in the amount of sediment in the reservoir prior to the dam Iron gate I was accompanied by an increase in the concentration of the following metals: antimony, arsenic, chromium, europium, neodymium and samarium.VII International Conference on Radiation in Various Fields of Research : RAD 2019 : book of abstracts; June 10-14, 2019; Herceg Novi, Montenegr