Special Issue

 

  

 

 

 

 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina

 

 

Special Issue

 

 

Publication date: October 2014

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Table of contents


Solvent-induced transformations in feromagnetically coupled (Ni4L4) clusters Plenary lecture

Cindrić Marina

Abstract: To date several magnetic systems with SMM-type behaviour based on polynuclear complexes of the Mn, Fe, Ni, V and Co or mixed metals have been described. Their synthesis poses a number of challenges, often related with inability to predict the  exact  cluster  structure  due  to  potentially  variable  outcomes  of  self–assembly process.  Owing  to  a  wide  range  of  their potential applications, e.g. in data storage, memory devices, switches and sensors, considerable attention has been devoted to the targeted synthesis of such systems. The importance and great influence of the solvent on modulation of the SMM's magnetic  features  was  first  described  in  1999  by  Olivier Khan1, who introduced the concept of a “magnetic sponge” to describe magnetic materials that can reversibly release and reabsorb both coordinated and uncoordinated solvent molecules. Importantly, it was shown that these processes are accompanied by the structural changes related to a cleavage/formation of the coordination bonds which subsequently also affect the magnetic properties.2,3 Among different cluster types that can exhibit SMM features, cubane–like magnetic clusters with [Ni43–O)4] core are especially well–studied class. The cubane–like core of nearly all investigated tetranuclear Ni(II) complexes includes four identical μ3–O bridges originating from –OH or –OR moieties. Previous studies have unveiled that the symmetry of [Ni4O4] core and the differences in the Ni–μ3–O–Ni angles play a crucial role in the intramolecular magnetic interactions. Namely, it was shown that the ferromagnetic interactions are associated with the core angles close to 90°, whereas the antiferromagnetic interactions involve larger angles. This was also corroborated by the latest investigation of [Ni4L4(solv)4] type of complexes which exhibit a switching of the spin ground state from S=4 to S=0 at ambient temperature, triggered by the reversible exchange of the coordinated solvent molecules (MeOH vs. H2O).4 Although the structural alterations induced by such solvent exchange were subtle, substantial changes of the physical and chemical properties have been established. Our latest investigations were directed to synthetic procedures, interconversion scenarios of reabsorption and exchanging solvent molecules, structural and magnetic studies of a new family of Ni(II) compounds based on cubane–like clusters. Depending on synthetic conditions different cubane–like clusters [Ni4L4(ROH)4], [Ni4L4(H2O)2], [Ni4L4(ROH)2(R’OH)2] and [Ni4L4(ROH)2] (H2L=tridentate Schiff base ligand, N–(2–hydroxy–5–methylphenyl)salicylideneimine, R= -CH3, -C2H5, -C3H7, -C4H9 i –C5H11) were isolated.The exhibited solvent–induced transformations of the clusters have been studied by SCXRD (at 150 K and at 296 K) and PXRD, TG/DSC, DVS, SQUID magnetometry, Hot–stage microscopy, IR as spectroscopic method and quantum chemical calculations. All experiments are showed possibility to come again to the well–defined initial state exposing clusters to methanol vapours, in turn. 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 2-3.

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Investigation of antioxidative and cell signaling properties of bioactive compounds from aromatic herbs Plenary lecture

Miloš Mladen

Abstract: Reactive oxidizing species (ROS), which are generated during the natural process of aerobic metabolism in living cells, can significantly damage the vital macromolecules and change their functions. As a result of oxidative stress and inhibition of certain enzyme activities, may occur the chronic diseases such as cancers, atherosclerosis, rheumatic and neurodegenerative diseases, diabetes, etc. Today, it is suggested that the control of harmful oxidation processes in living organisms is possible by preventive consumption of different antioxidant compounds through diet. Therefore, there is great interest in the study of biologically active compounds derived from food. The goal of such research is the isolation, fractionation and identification of chemical compounds and testing their biological activity such as antioxidant effect and inhibition of the enzyme activity of the selected enzyme (acetylcholinesterase, catalase, tyrosinase, superoxide dismutase, protein tyrosine kinase, etc.). In order to achieve this specific objective the conventional extraction methods were used. Separation of the active components is done by fractionation using chromatographic techniques. The chemical composition and the content of the fractions were carried out by chromatography and mass spectrometry and spectroscopy (GC/MS, HPLC/MS, UV/VIS). Antioxidant activity was examined using standard methods: DPPH (free radical scavening), FRAP (ferric reducing ability of plasma), TBARS (thiobarbituric acid method), etc. The inhibition of enzyme activity was examined by corresponding UV/VIS spectrophotometric methods. Enzyme kinetics are mainly studied by Michaelis-Menten model. Since many types of chronic illnesses are a result of disruption of signaling pathways which control the normal cell function, the investigation of biologically active compounds derived from food can be very interesting from several aspects. The possible identification of new antioxidant and inhibitor of the enzyme activities of selected enzymes could find application in the food and the pharmaceutical industry for the preparation of healthy food and natural remedies. 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 4-5.

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Complexes of transition metals with pyrazole derived ligands: synthesis, physico-chemical characterization and potential application Plenary lecture

Jaćimović Željko

Abstract: Metal complexes with pyrazole and its derivatives have recently attracted the attention of many authors, which is supported by a large number of published scientific papers, as well as by several reviews. However, these compounds are interesting not only from a theoretical, but also practical aspect. Specifically, pyrazoles are the components of many drugs (especially antipyretics and antirheumatics, herbicides and fungicides, and some pyrazole derivatives can be used as extragents of various metal ions. Most recently, the knowledge about biocoordination chemistry of pyrazole and its derivatives has been expanded. Among these, some macrocyclic pyrazole ligands are significant in biochemistry of oxygen transport, as well as those  which  participate in the formation of three-dimensional structure around the active centre of copper proteins (enzymes). Bearing in mind the considerable interest that exists for complexes with pyrazole derivatives ligands, this paper is aimed to review the newly synthesized complexes (by our research group) of Cu(II), Zn(II), Cd(II), Hg(II), Ni(II), Co(II) with some di-and tri-substituted pyrazole derivatives, to describe the syntheses and physic-chemical characterization of complex compounds obtained. The potential anticancer activity has been investigated in the selected group of complex compounds (complexes with pyrazolone ligands). The second selected group of compounds was investigated in relation to the potential biological activity (fungicidal activity) on pathogenic fungi Phomopsis viticola Sacc, which is the cause of leaf spot disease of grapevine and Botryosphaeria dothidea that causes fruit rot of olives. 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 6-7.

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Conducting polymers and their applications Plenary lecture

Toparre Levent

Abstract: Conducting polymers attracted great attention in many research fields owing to their overwhelming characteristics like ease of processability, ability of conduct electricity, low cost, straight forward preparation techniques. Our research interests are conducting polymer based electrochromic devices, solar cells, organic light  emitting diodes and biosensors. Polymers having one of the three complementary colors (red, green, and blue) in the reduced state and high transmissivity in  the oxidized state  are key materials towards use in electrochromic devices and displays. For potential  application  of electrochromic materials in display technologies, one should have to create the entire color spectrum and this can be only achieved  by having materials with additive or subtractive primary colors in their neutral states. To obtain a green color there should be at least two simultaneous  absorption bands. Although the neutral state color is of great importance, the transmittance in the oxidized state is crucial too. Biosensors based on conducting polymers have advantages over conventional laboratory based assays. The conventional methods are time consuming, expensive, required well trained personnel and not used for real time measurements. Nevertheless, biosensors are inexpensive, portable with minimized design, easy to handle, selective and sensitive. In our group, a wide variety of biosensors were emerged as conducting polymer based enzyme biosensors. For these purposes, many conducting polymers which have specific groups were designed and synthesized. These polymers were utilized as immobilization matrices for biosensor construction. During immobilization, several modification structures were used in biosensor fabrication to achieve the most effective surface design for target biosensors. Solar cells basically convert sunlight into electricity. With the absorption of light donor molecule’s electrons are excited from HOMO to LUMO to generate excitons. Excitons dissociate into holes and electrons. Electrons move through the acceptor molecule while the holes travel along the donor molecule. Charge carriers reaching to respective electrodes are collected. OLEDs on the other hand work oppositely generating light upon potential application. Recent developments in The Center for Solar Energy Research and Applications, METU on the OPVs and OLEDs are discussed.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 8-9.

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Catalysis: "Awakening Affinities" for Organic Synthesis Plenary lecture

Bates W. Roderick

Abstract: The synthesis of a complex molecule without the use of catalysis would, nowadays, be unthinkable. Catalytic reactions, from the mundane to the exotic, are ubiquitous in the field of organic synthesis. In particular, the use of transition metal catalysis has revolutionised the ways that we think about the formation of carbon-carbon bonds. We are currently employing a wide variety of metals to achieve mild and selective bond formation. This includes palladium, rhodium, osmium, iridium, platinum, silver and gold. In addition, we have developed methods using Lewis acidic main group metal catalysts. A selection of catalytic reactions and their applications will be presented.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 10.

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Application of Six Sigma in Control of Enzymes Determination Oral presentation

Jozo Ćorić

Abstract: Clinical Chemistry is backbone in the medical treatment, diagnostics or prevention.Test for several serum enzymes are used in the differential diagnosis of disease. Laboratory attempts to improve quality aim to reduce diagnostic errors and decrease turn around time with traceability of all laboratory procedures and to assure the safety of patients. Not all the of many approaches to quality control are equally effective. A critical limitation of the statistical quality control is that they are ineffective in detecting and contoling mistakes. Statistical quality contol can effectively contol process variation, but it cannot detect or prevent most mistakes. Six sigma belongs to statistical quality control and provides a new methodology for measuring process performance and refines earlier methodologies for making process improvements.The Sigma concept provides a universal methodology for measuring quality by counting the defects results. The performance of all processes can be characterized on the „Sigma scala“ ranga from 2 to 6. Sigma was calculated using Ricos quality requirements. In terms of Sigma, if a method has a value less than three is considered to be unreliable and should not be used in routine laboratory partice. Six Sigma provides benefits over prior approaches to quality menagement, it also creates newer challengens for laboratory practitioners.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 12.

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Protective Effect of Cabbage Extract Against Amiodarone Induced Oxidative Stress in Rat Brain Oral presentation

Ismet Burcu Turkylimaz

Abstract: Amiodarone is the most commonly prescribed antiarrhythmics effectively treating atrial and ventricular fibrillation. It has many important side effects, including hepatotoxicity, thyroid and neuropathic problems. Cabbage (Brassica oleracea L. var. capitata) is one of the most important vegetable in worldwide. Due to its antioxidant and antiinflammatory activities, cabbage has a widespread use in traditional medicine. In this study, we aimed to investigate the effects of amiodarone and cabbage extract on rat brain. Female Sprague-Dawley rats were randomly divided into four groups as follows: control group receiving corn oil: cabbage extract (500 mg/kg/day) given group: amiodarone (100 mg/kg/day) given group: amiodarone + cabbage extract (in same dose) given group. Cabbage extract and amiodarone were given by gavage to the rats for 7 days. Amiodarone was given to the animals one hour after cabbage extract administration during the experimental period. All animals were sacrificed on the 8th day. Brain tissues were taken and homogenized in saline. Brain lipid peroxidation and protein carbonyl levels, catalase, superoxide dismutase, adenosine deaminase, xanthine oxidase and myeloperoxidase activities were increased while sodium potassium ATPase activity was decreased in amiodarone group. Administration of cabbage extract reversed these effects. These results demonstrated that administration of cabbage extracts is a potentially beneficial agent to reduce the brain damage induced by amiodarone.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 13.

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Automated determination of active compounds in pharmaceutical formulations by flow injection analysis Oral presentation

Lea Kukoč Modun

Abstract: Flow injection analysis (FIA) is an automated technique with numerous applications in quantitative chemical analysis. From the beginning in 1975 when Hansen and Ružička introduced FIA for the first time, till today, more than 17000 scientific papers and 20 monographs have been published. FIA is a kinetic method of analysis; signal is recorded in the moment when the chemical reaction did not proceed to thermodynamic equilibrium. In contrast to the conventional continuous flow procedures and batch methods, FIA do not rely on complete mixing of sample and reagent(s) (physical homogenization). In recent years, more strict regulation related to the quality control in pharmaceuticals led to increasing demands on automation of the analytical assays carried out in appropriate control laboratories. FIA became a versatile instrumental tool that contributed substantially to the development of automation in pharmaceutical analysis due to its simplicity, low cost and relatively short analysis time. In this work the developed flow injection methods with spectrophotometric detector for the determination of thiol compounds (active substances in pharmaceutical formulations) will be presented. The selectivity of the developed methods based on the reaction mechanism will be discussed. 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 14.

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Anaerobic digestion of waste from leather industry: biogas production potential by bench and pilot scale experiments Oral presentation

Melina Džajić Valjevac

Abstract: Meat waste is the most common source of biological waste in the world, including Bosnia and Herzegovina. Leather industry contributes to the production of biological waste mainly through the processing of raw hides and the treatment of wastewater. These residuals are difficult to be properly disposed and solutions such as thermal treatment, because of high water content, are less appealing. Anaerobic digestion could represent an attractive solution from the environmental and economic perspective. Anaerobic digestion of leather industry wastes (raw hides fleshing and wastewater treatment surplus sludge) have been investigated using bench scale Biochemical Methane Potential tests (BMP) and a 1 m3 inclined plug flow pilot reactor under mesophilic conditions (35 ±1°C). The experiments revealed the possibility of stable biogas production. In detail, at maximum stable loading rate, the anaerobic treatment of 35-70 kgd-1of waste generated up to 400–450 ld-1 of biogas, with a yield compared to maximum theoretically achievable of 70% (0,17-0,20 lCH4gCOD-1). Recorded concentrations of ammonia and sulfide did not reach values to produce evident inhibitory effects and to compromise the overall process.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 15.

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Automated microfluidic synthesis of N-succinimidyl 4-[18F] fluorobenzoate: a protein labelling agent Oral presentation

Rumeysa Tutar

Abstract: Biomolecules labeled with radioactive fluorine 18F are an invaluable tool for the molecular imaging of physiological processes with positron emission tomography (PET). N-succinimidyl 4-[18F] fluorobenzoate ([18F]SFB) is one of the most popular 18F-synthons used for the labeling of free amine groups of biomolecules2. Manual synthesis of  [18F] SFB is, however, laborious work and leads to excess radioactivity exposure. The use of microfluidics for automated radiosynthesis has recently gained popularity in the research  community. An automated procedure of  [18F]SFB synthesis has been developed starting from (4-ethoxycarbonyl)-N,N,N-trimethylbenzeneaminium triflate using a platform  consisting  of  the microfluidic module Advion Nanotek (USA) and a conventional radiosynthetic module Nuclear Interface (Germany). To test the reactivity of the thus obtained [18F]SFB, we used it to prepare [18F] fluorobenzoylated human serum albumin ([18F] FB-HSA), a blood pool imaging agent. [18F]SFB was obtained within 90min synthesis time (including purification) in 13±8% isolated yield and >95% radiochemical purity. Conversion of [18F] SFB into [18F] FB-HSA was 26.9% within 30min. Radiochemical purity of gel-filtration-purified [18F] FB-HSA was >97%. An automated synthesis procedure suitable for the preparation of [18F]  SFB has been developed. This protocol can be used to label biomolecules for research purposes.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina 42, 16.

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Electrochemical synthesis and study of polyanilines with covalently attached acidic groups Oral presentation

Gutić Sanjin

Abstract: Electrochemical copolymerization of aniline and its carboxylic acid and hydroxyl derivatives, postpolymerization electrochemical treatment of polyaniline films as well as eletrochemical properties of obtained films are discussed. Synthesized copolymer films with carboxylic, hydroxyl and sulfonic groups were investigated by voltammetric and impedance techniques in electrolytes of different pH, in order to determine pH dependence of their electrical and redox properties. All co-monomers show inhibiting effect on electrochemical polymerization rate of aniline, thus making the ratio of aniline to co-monomer important variable. Copolymers with carboxylic and hydroxyl groups have well defined redox behavior in solutions of higher pH, while they remain fairly insoluble. Sulfonic acid derivatives also show redox activity in solutions of higher pH but cannot sustain as insoluble freestanding films.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 17.

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Determination of water content with 774 KF Automated Oven Sample Processor in samples that are Maillard reaction producing Oral presentation

Jurković Josip

Abstract: The water is obligatory quality indicator of all foodstuffs. However, its determination is not always easy because it could result in loosing of volatile compounds (heating) sample degradation or transformation. Results from heating methods will often show amount of all volatile compounds and not just water. The second problem caused by heating is Maillard reaction, during which water is produced in samples with high sugar and protein content. It is hard to distinguish water that is originally from sample and water produced by Maillard reaction. That asks for determination of two “kinds” of water: originally present in a sample and water produced in Maillard reaction. Karl Fischer titration is the most promising method for water determination which relies on chemical reaction of water. Our investigation used the method that combines the 774 Oven Sample processor (Metrohm) with coulometric Karl Fisher titration and as the control method classical volumetric Karl Fischer titration. The model systems were different combinations of whey protein and maltodextrin. Some 550 determinations, including parallels were made. The results have indicated, depending on proteins-maltodextrin ratio, a range of 0.34% to 0.80% of total sample water was produced in Maillard reaction.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 18.

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Spectrometric Characterization ofIron Nanoparticles Preparation using Chelating Ligands Oral presentation

Sanda Rončević

Abstract: Recent research has shown that nanoscale iron particles are effective material for the transformation of wide array of common environmental contamination in water systems. Zero valent  iron nanoparticles (nZVI) are typically prepared by reducing Fe(II) of Fe(III) in an aqueous phase using sodium borohydride. In order to prepare nZVI of desired stability, a variety of stabilizing agents, surfactants or capping agents are employed in synthesis steps. The objective of this work is to provide comparison and quality control of iron nanoparticles produced under different experimental conditions. Therefore, the synthesis of nZVI from aqueous solution of iron salts after addition of different chelating  ligands such as EDTA, dipicolinic and citric acid was studied. The resulting nanomaterials were characterized by scanning electron microscopy (SEM) which showed that the dendritic structure of nZVI in nano scale was favored in EDTA experiment. Preparation of nZVI was also tested by addition of selected heavy metals. Concentrations of metals in remaining aqueous solution were determined by inductively coupled plasma optical emission spectrometry (ICPOES). The metal removal efficiency of nanoparticles was calculated from the observed changes in concentration.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 19.

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Hydrothermal growth of ZnO nanorods on Zn substrates and their application in degradation of azo dyes under ambient conditions Oral presentation

Igor Djerdj

Abstract: A new type of catalytic material, large-scaled ZnO nanorod arrays grown on self-source substrate, was directly synthesized by a facile hydrothermal approach. The catalytic activity of the ZnO nanocrystals with different exposed surfaces, including ZnO hexagonal nanorods with exposed reactive {0001} facets, hexagonal ZnO nanopyramids with the nonpolar {0110} planes, and pencil-like morphology with exposed {1011}  polar  planes, was tested towards the degradation of the azo dyes (Congo red (CR) and methyl orange (MO)). The aqueous azo dyes can be degraded efficiently under ambient conditions, requiring neither light illumination nor additional energy (agitation, ultrasonic,  etc.). Systematic experiments suggested that the dye degradation proceeds through the electron transfers from the anionic dye molecules to the catalyst and then to electron acceptors such as dissolved oxygen. It strongly depends on the exposed polar surfaces of the ZnO nanocrystals, giving rise to the relative higher catalytic activity and stability of the ZnO hexagonal nanopencils. The present ZnO nanorods arrays grown on Zn substrate requires no additional reagents or external energy input, which hence provides a potentially low-cost  alternative for the remediation of azo-dye effluents. 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 20.

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Supercritical fluids as a tool of process intensification and sustainable technologies Oral presentation

Maša Knez Hrnčić

Abstract: Using supercritical fluids (SCF) as solvents in chemical processes means an advantage in many points of view. It offers health, safety, environmental and also chemical benefits. Commonly SCFs are termed as green solvents. Using high pressure as a processing tool surpasses legal limitations for solvent residues and restrictions on use of conventional solvents in chemical processes. Additionally, particulate products can be also achieved by means of SCF processing. The contribution will give a limited overview of applications of sub-and supercritical fluids and will present energy savings compared to conventional production methods. Considering above mentioned facts, supercritical fluids could certainly be applied as a substitution of conventional solvents in extractive and non-extractive processes as a nontoxic, inexpensive, nonflammable, and nonpolluting solvents. Many applications such as high pressure sterilization, jet-cutting, thin film deposition for microelectronics, and the separation of value-added products from fermentation broths in the biotechnology field have been fully developed and commercialized. Particle formation processes using high pressures in presence of supercritical fluids may overcome several drawbacks of conventional particle size reduction processes.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 21.

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Preliminary chemical analysis of new discovered siderite meteorites from Croatia and Bosnia and Herzegovina Oral presentation

Budimčić Jelena

Abstract: Ten samples of iron meteorites recently discovered on the territory of Croatia and one sample form Bosnia and Herzegovina were analyzed by three techniques: a) polishing and etching by ferric chloride, b) X–ray powder diffractometry (XRD) and c) inductively coupled plasma with atomic emission spectroscopy (ICP-AES). The goal of this work was to determine qualitative and quantitative composition of selected meteorite samples, and to attribute the samples structural and chemical group of iron meteorites if possible. The analyses have shown that all eleven samples contain iron and nickel as macroelements in one to one ratio, with the exception  of a sample  containing abundant manganese. All samples contain high amount of iridium. Most of the analyzed samples belong to the structural group of ataxites, containing almost pure taenite phase, while chemical groups could not be established with certainty due to lack of data on the quantity of siderophile elements like gallium, gold and germanium, which are main parameters for the chemical classification of iron meteorites.

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 22.

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Atomic spectrometry as a tool for archaeological material description Oral presentation

Nemet Ivan

Abstract: Elemental composition of archaeological material is very useful when trying to answer the question of manufacture, provenance and/or purpose of the object of interest. Analytical atomic spectrometry methods have an extremely important role in the characterization of items of cultural heritage. Also, they are widespread and very useful for simultaneous determination of elements. They are mostly destructive which is a posing problem when analyzing cultural heritage objects. Inductively coupled plasma atomic emission spectrometry, ICP-AES and inductively coupled plasma-mass spectrometry, ICP-MS were used for determination of selected element content in fragments of iron artefacts such as slag and bloom which are dated to the Bronze Age, and La Tène culture, and were collected during extensive archaeological excavations under the supervision of the Zagreb City Museum. Instrumental working conditions were optimized after preliminary selection of the most appropriate emission lines for the selected elements. Microwave assisted digestion was used for the preparation of sample solutions and the analytical procedure was controlled with standard reference materials. Multivariate statistical analysis allowed classification of obtained results in groups which consisted of ceramic, ceramic-rich slag and bloom material. As an example, one sample (No3170) consists of Fe (35.5%), Al (4.4%), Mn (0.5%), Ti (0.3%), Cr (99.5 ppm), Zn (29.5 ppm), La (24.4 ppm), Ce (57.32 ppm), Pr(6.71 ppm), Eu (1.43 ppm).

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 23.

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Content of Fe, Cu and Pb in human teeth enamel and dentin in relation to the age Oral presentation

Olovčić Almir

Abstract: The content of iron, copper and lead was determined in 25 human teeth samples from Sarajevo and Bihać by using flame atomic absorption spectrometry (FAAS). The aim of this study was to test whether the content of these metals increased with the age of the subjects. Samples were split on enamel and dentin by burning at 500°C and by using mechanical separation. For the dissolution, concentrated nitric acid and hydrogen peroxide was used. Concentration of Pb was below detection limit using the applied method in 7 dentin samples and even 18 enamel samples. It is for these reasons that we took as relevant results of Pb content those in dentin and not the ones in enamel. Results have shown cumulative effect for all three metals. This effect is more pronounced in enamel than dentin since in enamel the concentration of Cu and Fe was twice as high. The average concentration of Fe in enamel was 51.54, 73.87,  73.97 and  122.40 ppm;  while the concentration of Cu was 0.19, 0.33, 0.72 and1.53 ppm for persons aged 18-30, 31-59, 51-70 and over 70 years, respectively. A similar trend with less pronounced differences was detected in dentin for Fe and Cu while the concentration of Pb in dentin was 0.18, 1.39, 2.34 and 4.41 ppm for the specified age. 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 24.

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A New Approach for The Synthesis of Ceramic Materials Oral presentation

Yusuf Nur

Abstract: Polycarbynes and polysilynes have previously been shown to be polymeric precursors to diamond, diamond-like carbon (DLC) and silicon carbide production. The most important properties of these polymers are to form tough, hard-wearing ceramic materials with high thermal stabilities upon moderate heating. Poly(methyl  silyne) (PMSi) and polyhydridocarbyne (PHC) are the most known pre-ceramic polymers. PHC forms diamond and DLC, while PMSi can be easily converted to SiC upon pyrolysis. Poly(silyne-co-carbyne) (PSC) simply forms silicon carbide without requiring the addition of more carbon species and a catalyst since it already contains silicon and organic carbon on its backbone. Here, we report a simple method for producing silicon carbide using PSC, which contains both silyne and carbine on its backbone. PSC is simply synthesized using trichloro(dichloro methyl) silane (TCS), electricity, a solvent and an electrolyte. Coating of PSC on any surface is very easy and cheap due to the solubility of it in common organic solvents. UV/Vis spectroscopy, 1H-NMR and GPC analyses were shown the structure of PSC. Ceramic film was obtained by sintering of the polymer at 1000, 750 or 500oC depending on sinter atmosphere whether being inert or air. This study was supported by TUBITAK with project number 211T108).

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 25.

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Poster presentations: Analytical and Environmental Chemistry

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 26-60.

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Poster presentations: Biochemistry and Biotechnology

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 61-80.

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Poster presentations: Inorganic Chemistry

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 81-94.

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Poster presentations: Biological Chemistry 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 95-101.

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Poster presentations: Organic and Medicinal Chemistry

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 102-131.

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Poster presentations: Physical and Theoretical Chemistry

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 132-150.

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Poster presentations: Chemistry of Advanced Materials 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 151-154.

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Poster presentations: Chemical Engineering 

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 155-161.

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Poster presentations: Education in Chemistry

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 162-166.

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Poster presentations: Topics related to Chemistry

Bulletin of the Chemists and Technologists of Bosnia and Herzegovina Special Issues, 167-170.

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