Papers by Ljubisa Ignjatovic
Metals
A dispersive solid-phase microextraction (DSPME) sorbent consisting of poly(1,6-hexanediol diacry... more A dispersive solid-phase microextraction (DSPME) sorbent consisting of poly(1,6-hexanediol diacrylate)-based polymer microspheres, with embedded graphene microparticles (poly(HDDA)/graphene), was synthesized by microfluidic emulsification/photopolymerization and characterized by optical microscopy and X-ray fluorescence spectrometry. This sorbent was applied for simple, fast, and sensitive vortex-assisted DSPME of rare earth elements (RREs) in coal fly ash (CFA) leachate, prior to their quantification by inductively coupled plasma mass spectrometry (ICP-MS). Among nine DSPME variables, the Plackett–Burman screening design (PBD), followed by the central composite optimization design (CCD) using the Derringer desirability function (D), identified the eluent type as the most influencing DSPME variable. The optimum conditions with maximum D (0.65) for the chelating agent di-(2-ethylhexyl) phosphoric acid (D2EHPA) amount, the sorbent amount, the eluting solvent, the extraction temperatur...
Catalysts
Unmodified natural silicates (bentonite, kaolin, clinoptilolite and diatomites) were tested as ad... more Unmodified natural silicates (bentonite, kaolin, clinoptilolite and diatomites) were tested as adsorbents for the organic pollutants in water tables using Methylene Blue (MB) as the model adsorbate. Among the selected materials, bentonite adsorbed as much as 237 mg/g, confirming its excellent suitability for pollutant removal. Spectral evidence confirmed successful MB immobilization at the bentonite surface. Furthermore, the thermal treatment of MB-saturated adsorbent in an inert atmosphere at 700 °C produced a carbon/silicate composite. EDX confirmed the formation of the nitrogen-doped carbon overlay on the silica scaffold and the obtained composite material was probed as an electrode material for oxygen reduction in an alkaline solution. Reduction proceeded via a two-electron mechanism with the main product being HO2−, a known nucleophile, which was subsequently used to degrade/demethylate MB. The composite showed a considerable 70% MB removal rate after an hour of electrochemical...
Pharmaceutics, 2021
A critical step in the production of Esomeprazole powder for solution is a period between the fil... more A critical step in the production of Esomeprazole powder for solution is a period between the filling process and lyophilization, where all vials, partially closed, are completely exposed to environmental influences. Excessive instability reflects in pH value variations caused by oxygen’s impact. In order to provide pH control, which consequently affects drug stability, Esomeprazole batches, produced in the same way, were kept in partially closed vials for 3 h at temperatures of 20 °C and −30 °C, after which they were lyophilized and stored for long-term stability for 36 months. The aim of the presented study was to apply a deep-learning algorithm for the prediction of the Esomeprazole stability profile and to determine the pH limit for the reconstituted solution of the final freeze-dried product that would assure a quality product profile over a storage period of 36 months. Multilayer perceptron (MLP) as a deep learning tool, with four layers, was used. The pH value of Esomeprazole...
JOURNAL OF ENGINEERING & PROCESSING MANAGEMENT, Jan 30, 2018
Smanjenje emisije gasova staklene bašte i korišćenje obnovljivih izvora energije su danas jedni o... more Smanjenje emisije gasova staklene bašte i korišćenje obnovljivih izvora energije su danas jedni od najizazovnijih zadataka u oblasti nauke o životnoj sredini. U tom smislu biogoriva su veoma obećavajuće alternative gorivima koja se sada upotrebljavaju. Uspešna komercijalizacija i tržišno prihvatanje biogoriva zavise od prisustva jona koji imaju negativan uticaj na delove motora kao i na životnu sredinu. U tom smislu jonska hromatografija ima značajnu ulogu u kontroli kvaliteta biogoriva. Pored određivanja sadžaja katjona, glicerola i antioksidanasa u biodizelu, jonska hromatografija sa direktnim injektiranjem omogućava određivanje hlorida i sulfata u bioetanolu. Takođe, jonska hromatografija postaje dragocena tehnika u monitoringu i procesnoj kontroli uzoraka iz reaktora biogasa. Ovaj rad prikazuje primenu jonske hromatografije kombinovane sa "inline" pripremom uzoraka za određivanje anjona i katjona u biogorivima i isparljivih organskih kiselina u procesnim rastvorima: tragovi anjona u benzin/etanol smeši mogu da se odrede do nivoa ppb nakon eliminacije uticaja matriksa; alkalni i vodom ekstraktabilni zemno-alkalni metali u biodizelu su određivani posle ekstrakcije azotnom kiselinom i naknadne dijalize; u uzorcima iz reaktora biogasa, organske kiseline malih molarnih masa koje potiču od biodegradacije organske supstance mogu se odrediti primenom jon-istiskujuće hromatografije posle dijalize ili ultrafiltracije.
Journal of The Serbian Chemical Society, 2020
Seventeen water-soluble substances (sodium, ammonium, potassium, magnesium, calcium, formate, met... more Seventeen water-soluble substances (sodium, ammonium, potassium, magnesium, calcium, formate, methanesulfonate, glyoxylate, chloride, nitrite, nitrate, glutarate, succinate, malate, malonate, sulfate, and oxalate) in 94 samples of particle matter in the ambient air, collected for ten months, in a suburb of Belgrade (Serbia), were determined by ion chromatography. To apportion the sources of the air pollution, the log-transformed data were processed by applying multivariate techniques. Principal component and factor analysis identified three main factors controlling the data variability: stationary combustion processes with the highest loadings of oxalate, malonate, and malate; landfill emission and secondary inorganic aerosol characterized by high levels of ammonium, nitrate, and sulfate; and a contribution of mineral dust composed of magnesium, calcium, and chloride. The hierarchical cluster analysis pointed out a differentiation of the samples into five groups belonging to differe...
Journal of the Serbian Chemical Society, 2011
Arsenic reduction in drinking water can include treatment by adsorption, switching to alternative... more Arsenic reduction in drinking water can include treatment by adsorption, switching to alternative water sources, or blending with water that has a lower arsenic concentration. Commercial sorbents MTM, Greensand and BIRM (Clack Corporation) were modified with zirconium and titanium after activation. The modifications were performed with titanium tetrachloride and zirconium tetrachloride. The modified sorbents were dried at different temperatures. The sorption of arsenate and arsenite dissolved in drinking water (200 μg L-1) onto the sorbents were tested using a batch procedure. After removal of the sorbent, the concentration of arsenic was determined by hydride generation atomic absorption spectrometry (HG-AAS). Zirconium-modified BIRM showed the best performance for the removal of both arsenite and arsenate. Modification of the greensand did not affect arsenic sorption ability. Zirconium-modified BIRM diminished the concentration of total As to below 5 μg L-1 .
Journal of the Serbian Chemical Society, 2002
In the present work the structural transformations of malvin in aqueous acetate buffer solutions ... more In the present work the structural transformations of malvin in aqueous acetate buffer solutions were investigated over a wide pH range under in vitro conditions using electronic absorption spectroscopy. In addition to the spectroabsorptiometric investigation, the voltammetric behavior and the mechanism of the redox process of this molecule were studied, in order to define its antioxidant properties. The electronic absorption spectra reveal that the structural changes of malvin, caused by changes in the pH of the medium, lead to changes in the voltammetric behaviour of this molecule. The dependence of the oxidation potential of malvin on pH, which can be explained by the presence of different electroactive molecular structures of malvin at different pH values, indicates different mechanisms of the electrode process. The voltammetric activity of malvin is compared semiquantitatively with the voltammetric activity of a standard synthetic antioxidant, BHA, and a natural antioxidant, quercetin.
Journal of the Serbian Chemical Society, 2012
The single agent extractions of major and trace metals from soil sample were conducted by means o... more The single agent extractions of major and trace metals from soil sample were conducted by means of rotary mixer and ultrasonic bath with sonication time of 10, 20, 30, 40 and 50 min. The sequential extraction according to the BCR scheme was undertaken. The obtained soil extracts were analyzed by ICP-OES and according to the results the rotary mixer assisted extraction was more efficient in the case of alkaline-earth elements. However, by the use of ultrasound several times higher amounts of matrix elements (Fe, Al and Mn) and heavy metals predominantly associated with Fe, Al and Mn oxyhydroxides were extracted. The increase of the sonication time failed to improve extraction yields. The changes of the conductivity, pH, oxidoreduction potential, particle size diameter and zeta potential of colloid particles, with the sonication time increase were measured. The extraction mechanism and expressed selectivity of ultrasound is discussed and explanation is suggested.
Central European Journal of Chemistry, 2008
Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solu... more Lutetium has been determined by differential pulse anodic stripping voltammetry in an acidic solution containing Zn-EDTA. Lutetium (III) ions liberated zinc (II), which was preconcentrated on a hanging mercury drop electrode and stripped anodically, resulting in peak current linearly dependent on lutetium (III) concentration. Less than 0.4 ng mL−1 lutetium could be detected after a 2 min deposition.
Central European Journal of Chemistry, 2011
This paper presents the extraction of cations from a soil sample, type ranker on serpentinite, in... more This paper presents the extraction of cations from a soil sample, type ranker on serpentinite, in deionized water, by use of three different extraction techniques. The first extraction technique included the use of a rotary mixer, the second technique involved the use of a microwave digestion system with different extraction temperatures, and the third technique employed an ultrasonic bath with different extraction times. Ion chromatography was used for determining the concentration of Li, Na, K, Ca, Mg and ammonium ions in soil extracts with subsequent determination of concentrations for all cations, except for ammonium ion extraction, conducted by Inductively Coupled Plasma-Atomic Emission Spectrometry. The results of cation extractions showed that microwave assisted extraction was most efficient for the Li, Na, K, Ca, Mg, Co, Mn, Ni, Pb and ammonium ions. Use of a rotary mixer for extraction was most efficient for Cd and Zn ions, while use of ultrasound bath was most efficient fo...
Bioresource Technology, 2000
Particles in the gas from a two-stage (separate pyrolysis and gasification) down-draft biomass ga... more Particles in the gas from a two-stage (separate pyrolysis and gasification) down-draft biomass gasifier were collected and characterized. Their concentration, geometries and chemical compositions were investigated. Special attention was given to features suspected to harm internal combustion (IC) engines fueled by the gas. The implications of the findings on engine wear are discussed.The majority (85%) of the total particulate matter
Journal of the Serbian Chemical Society, 2016
Two mechanical extraction techniques were used for the extraction of environmentaly interesting e... more Two mechanical extraction techniques were used for the extraction of environmentaly interesting elements from coal fly ash: shaking, in which the extraction process lasted from 6 to 24 hours, and ultrasonic sonication during 15 to 60 minutes, with water as extractant. The concentration of anions in fly ash extracts were determined by ion chromatography, while atomic absorption spectrometry was used for determination of: As, Pb, Cd, Ni, Cr, Zn, Cu, Fe, Mn and Al. The ultrasonic sonication yielded slightly higher amounts of extracted anions and Pb, Al, Mn and Fe, while shaking-assisted extraction was more efficient for the Cr, As, Zn and Ni ions. The changes in pH value, particle size distribution in colloid, zeta potential and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of fly ash particles in contact with water and different processes (adsorption, ion exchange, flocculation) that occur in environmental conditions. Princ...
Journal of the Serbian Chemical Society, 2016
This paper presents the extraction of major and trace elements from a coal sample, in deionized w... more This paper presents the extraction of major and trace elements from a coal sample, in deionized water, by using three different extraction techniques. Rotary mixing and ultrasonic extraction were examined for different extraction times, while the microwave assisted extraction was performed at different temperatures. Metal concentrations (Na, K, Ca, Mg, Al, Fe, Mn, Be, Cd, Co, Cr, Hg, As, Ni, Se, Sb and Pb) in a solution were determined by employing the inductively coupled plasma atomic emission spectrometry; whereas the results obtained for Na, K, Ca and Mg were compared employing ion chromatography. Comparing the rotary and ultrasonic-assisted extraction it is shown that the former is more efficient for the determination of Fe, Na and Pb, whereas the latter one has proven more efficient for the determination of Co and Cr ions. Microwave-assisted extraction has proven the most efficient method for any elements tested in coal. In addition, sequential extraction of elements was done u...
Journal of the Serbian Chemical Society, 2016
Three different techniques were applied for the aqueous extraction of anions from coal and fly as... more Three different techniques were applied for the aqueous extraction of anions from coal and fly ash: rotary mixer-and ultrasonic-assisted extraction with different duration time, and microwave-assisted extraction at different temperatures. Validation showed that the ion-chromatographic method was suitable for the analysis of anions in coal and fly ash extracts. The variations in the amounts of anions using different extraction times during rotary-assisted extraction were minimal for all investigated anions. The efficiency of ultrasound-assisted extraction of anions from coal depended on the sonication time and was highest at 30 min. The ultrasound-assisted extraction was less efficient for the extraction of anions from fly ash than rotary-assisted extraction. Increase of temperature in the microwave-assisted extraction had a positive effect on the amounts of all anions extracted from coal and sulphate from fly ash, while the amounts of fluoride and chloride in fly ash extracts decreased. The microwave-assisted extraction of coal at 150 °C was compared with standard ASTM methods, and results were in good agreement only for chloride. Changes in the pH value and conductivity during ultrasound-assisted extraction were measured in order to explain changes on the surface of coal particles in contact with water and different processes that occur under environmental conditions.
Journal of the Serbian Chemical Society, 2016
The aim of this paper was to simulate leaching of metals from fly ash in different environmental ... more The aim of this paper was to simulate leaching of metals from fly ash in different environmental conditions using ultrasound and microwave-assisted extraction techniques. Single-agent extraction and sequential extraction procedures were used to determine the levels of different metals leaching. The concentration of metals (Al, Fe, Mn, Cd, Co, Cr, Ni, Pb, Cu, As, Be) in fly ash extracts were measured by Inductively Coupled Plasma-Atomic Emission Spectrometry. Single-agent extractions of metals were conducted during sonication times of 10, 20, 30, 40 and 50 min. Single-agent extraction with deionized water was also undertaken by exposing samples to microwave radiation at the temperature of 50?C. The sequential extraction was undertaken according to the BCR procedure which was modified and applied to study the partitioning of metals in coal fly ash. The microwave-assisted sequential extraction was performed at different extraction temperatures: 50, 100 and 150?C. The partitioning of me...
and oxalate) in 94 samples of particle matter in the ambient air, collected over ten months, in a... more and oxalate) in 94 samples of particle matter in the ambient air, collected over ten months, in a suburb of Belgrade (Serbia), were determined by ion chromatography. To apportion the sources of the air pollution, the log-transformed data were processed by applying multivariate techniques. Principal component and factor analysis identified three main factors controlling the data variability: stationary combustion processes with the highest loadings of oxalate, malonate and malate; landfill emission and secondary inorganic aerosol characterized by high levels of ammonium, nitrate and sulfate; a contribution of mineral dust composed of magnesium, calcium and chloride. The hierarchical cluster analysis pointed out a differentiation of the samples into five groups belonging to different variables inputs. For the classification of ambient air samples using nine selected ions, the recognition ability of linear discriminant analysis, k-nearest neighbors, and soft independent modeling of cla...
International Journal of Electrochemical Science, Jul 1, 2011
ABSTRACT The 8-Hydroxyquinoline (8HQ) oxidation process has been investigated by Cyclic Voltammet... more ABSTRACT The 8-Hydroxyquinoline (8HQ) oxidation process has been investigated by Cyclic Voltammetry using a Glassy Carbon Paste Electrode (GCPE) as a working electrode. The theoretical study of the mechanism of electrochemical oxidation of 8HQ has been based on the AM1 semi-empirical quantum chemical computations of the heats of formation of the reaction intermediates, taking into account the influence of pH and solvation effects. We proposed that a two-electron irreversible process, controlled by diffusion of electroactive species, is responsible for an oxidation peak of 8HQ that appears in all cyclic voltammograms recorded on a clean electrode in the solutions of pH in the range 2 to 12 with a supporting electrolyte of Britton - Robinson Buffer/methanol. A single-electron oxidation of 8HQ leads, depending on pH, to the formation of various free radical species that combine to make dimers which, after being oxidized once more, give quinonoid-type compounds. Recording continuous cyclic voltammograms on the GCPE, pre-peaks appear as a consequence of dimer and quinonoid compounds formation. By applying Differential Pulse Voltammetry for 8HQ determination it was calculated that the limit of detection was 5.2 x 10-8 mol/L. For more sensitive quantitative determination of the investigated substance. Adsorptive Stripping Differential Pulse Voltammery can be used since it was found that after 300s - deposition time at 0.0 V vs. Saturated Calomel Electrode, a 2.1 times higher peak current than without deposition was obtained.
Plant Biosystems - An International Journal Dealing with all Aspects of Plant Biology
ABSTRACT An experiment was undertaken to evaluate the effect of liquid manure amendment on heavy ... more ABSTRACT An experiment was undertaken to evaluate the effect of liquid manure amendment on heavy metal accumulation in wheat and barley. For this purpose, both kinds of seedlings were grown simultaneously in a Petri dish, while wheat seedlings were also grown in pots containing unpolluted agricultural soil. All of the seedlings were irrigated with one of the three prepared solutions: artificial rainwater solution, heavy metal solution and liquid manure solution containing NH4NO3, H3PO4 and KOH along with equal amounts of heavy metals as in the second solution. Twenty days later, 1 g of plant tissue was digested with the mixture of HNO3 and H2O2 for ICP-OES/HG-ICP-OES analysis. The results showed that the uptake of arsenic and mercury was highest for both plants grown in a Petri dish. Furthermore, the wheat grown in a Petri dish also had a high content of nickel, cadmium and copper, while the pot-grown wheat contained high amounts of iron and manganese, probably due to the adsorption of nickel, cadmium, copper and mercury on soil phases. The lower uptake of all heavy metals was observed after the amendment of liquid manure, with the exception of manganese in wheat and mercury in all plants.
Journal of Agricultural Sciences, Belgrade, 2015
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Papers by Ljubisa Ignjatovic