STUDIA CHEMIA - Issue no.2 / 2020 - Table of contents
Editorial: Professor Ioan SILAGHI-DUMITRESCU (1950-2009)
We celebrate in June 2020 70 years from the birth of Professor Ioan SILAGHI-DUMITRESCU. Born in Botiz (Satu-Mare County) on June 1st 1950, he attended primary school in Botiz and high school in the city of Satu-Mare. He went on to receive a B. Sc. degree in Inorganic Chemistry in 1974 from the Faculty of Chemistry of the Babes-Bolyai University in Cluj-Napoca.
Between 1974 and 1977 he worked at the Intreprinderea de Ceramica Fina pentru Constructii Sanex in Cluj-Napoca, and in 1977 he joined the ranks of the Inorganic Chemistry Chair at the Faculty of Chemistry of the Babes- Bolyai University, where he also obtained a PhD degree in Chemistry in 1981. He was promoted full professor in 1994. It was in this position that he provided essential contributions to the modernization and reformation of the Faculty’s curricula, including the transition to the Bologna system and promoting new disciplines of study and new lines of study – including a strong direction in theoretical and computational chemistry. He led the Inorganic Chemistry Chair (1994-2007) and then served as Dean of the Faculty from 2008 to his premature departure on December 25th 2009.
Professor Ioan Silaghi-Dumitrescu’s contributions were in the area of inorganic and organometallic chemistry with transition metals and group 13- 15 compounds, including cumulenic and heterocumulenic systems with heavy elements, compounds with catalytic activity, compounds with biological activity. He was among the first researchers in Romania to approach chemistry with computing techniques (computational chemistry), starting with studies on the coordination behavior of organothiophosphoric ligands and evolving towards quantum chemistry. His results on the structure of postransitional-element clusters, organometallic clusters, cumulenic and heterocumulenic systems, nanotubes and calixarenes, were reported in almost 200 articles and are found in journals among the most prestigious across the globe. The majority of his research involved establishing strategies for chemical synthesis, rationalization and prediction of properties for a wide range of inorganic, organometallic, and organic compounds, which were obtained experimentally in his own group as well as in the groups of collaborators from within Romania and from abroad.
The Center for molecular modeling and computational quantum chemistry set up by professor Ioan Silaghi-Dumitrescu in 2007 (developed from the Laboratory for structure and molecular modeling he had set up in 1996) offers an infrastructure which is internationally competitive and has allowed for the consolidation of the theoretical chemistry school in Cluj, including collaborations with high-level researchers from the USA and China.
Dr. Ioan Silaghi-Dumitrescu was a visiting professor at Universidad Nacional Autonoma (UNAM) in Mexico (1995-1996), University of Georgia, Athens, Georgia (SUA) (1-2 months per year, 2000-2008), and visiting researcher at University of Nottingham (1992), Heidelberg University (1993- 1994). His collaborations spanned Universities in Toulouse, Rouen, Lille, Leipzig, Braunschweig, Koln, Budapest, Pecs, Beijing, Guanjou, Moskow (Idaho).
Professor Ioan Silaghi-Dumitrescu received the “Gheorghe Spacu” prize form the Romanian Academy in 1989 and the “Diploma de Onoare and G. Spacu Medal” form the Romanian Chemical Society in 2009. On March 24th 2006 he was elected corresponding member of the Romanian Academy. A scholarhip bearing his name is awarded annually to the top graduate of the Faculty of Chemistry and Chemical Engineering, and one of the largest amphitheaters at the Babes-Bolyai University is named after him.
This editorial was dedicated to the memory of Professor Ioan Silaghi- Dumitrescu, a highly respected member of the chemist’s community with many professional achievements, who will be perhaps remembered not only for his pioneering work in implementing the field of computational quantum chemistry and molecular modeling at Babes-Bolyai University, Faculty of Chemistry and Chemical Engineering, but also for the generosity of his academic spirit.
Studia UBB Chemia Editorial Board
The Effect of Halogen Substitution on the Bowl-to-Bowl Inversion, Molecular Structure and Electronic Properties of Sumanene
AKIN AZIZOGLU, DUYGU EMIR
Halogen (X: F, Cl, and Br) substituted sumanene derivatives were subjected to a detailed computational study, exploring the molecular structure, bowl-depths, bowl-to-bowl inversion dynamics, and electronic properties. Hybrid density functional (DFT, B3LYP, X3LYP and PBEKCIS) theoretical calculations were performed with an array of basis sets 6- 31+G(d,p) and cc-pVTZ. The bowl shaped geometry and other properties were significantly affected by the introduction of halogens (F, Cl, and Br). Especially, the bond length alternations (Δ1 and Δ2) in the hub benzene ring and flank benzene ring of halogenated sumanenes (2Xa, 2Xb, and 12X) show remarkable sensitivity as a function of halogen with a wide range of fluctuations (0.011 to 0.071 Å). The introduction of fluorine to sumanene influences the bowl-to-bowl inversion energies slightly. The size of halogens seems to chiefly control the bowl depth and bowl-to-bowl inversion dynamic. In contrast, the bond length alternations seem to be controlled by electronic factors and not by the size of the substituted halogen atoms. The frontier molecular orbitals (FMOs) and molecular electrostatic potentials (MEPs) were significantly affected by the introduction of halogen atoms.
Keywords: Sumanene, Halogens, Bowl-to-bowl inversion, DFT
Modelling of the Sugar Beet Pulp Drying Process
ADINA GHIRIŞAN, SIMION DRĂGAN, CONSTANTIN COŢA, ELENAMIHAELA NAGY, GYORGY ZOLTAN, VASILE MICLĂUŞ
The paper presents the drying model proposed for sugar beet pulp in the presence of hydrated lime within a range temperature of 333 and 368 K. The experimental results were used to identify the coefficients in the two-term exponential model, choose as the most appropriated model for our case. The relationships for the variation of the coefficients with temperature were determined. The equations of the mathematical model were used to establish the optimal drying time.
Keywords: sugar beet pulp, drying kinetics, drying rate, mathematical modeling
Modelling and Simulation of Methanol Production from Coke Oven Gas
LETITIA PETRESCU, DUMITRITA-AURA CRISAN
Coke Oven Gas (COG) is highly rated as a valuable by-product of coke production used in the steel industry. The production of methanol from COG-derived syngas has been investigated in the last period due to its practicality as well as to the recent interest in methanol over the past years. Two case studies, using COG and CO2 as raw-materials, are simulated and compared in the present study. In the first case the intermediate step is the dry methane reforming (DMR) while in the second case the intermediate step is steam methane reforming (SMR). The syngas obtained is furthermore converted to methanol. Beside the transformation of COG into methanol, the present study deals also with the CO2 emissions reduction, the CO2 generated in the COG combustion is captured using amine based gas-liquid absorption technology (e.g. methyl diethanolamine - MDEA)). ChemCAD process flowmodelling software was used as a tool to produce 250 t/day of methanol with purities higher than 99%. The results showed that the most advantageous technological route of COG and CO2 utilization is DMR, in which, a lower quantity of raw material (COG) and lower number of equipment is required to obtain the same amount of final product.
Keywords: Coke Oven Gas, Process Modelling and Simulation, Methanol production, Technical evaluation.
Mineral Waters Classification Using Fuzzy Linear Discriminant Analysis
ALEXANDRINA GUIDEA, RADU D. GĂCEANU, HORIA F. POP, COSTEL SÂRBU
Fuzzy linear discriminant analysis is efficiently applied for the characterization and classification of some Romanian and German mineral waters according to their mineral composition. The samples were successfully classified according to the degrees of membership and canonical scores. A correct classification rate of 88% was obtained when the samples were divided into four groups corresponding to origin and nature of samples. The proposed methodology based on the fuzzy sets theory may be considered as a promising tool with future applications in analytical chemistry and other related fields.
Keywords: Fuzzy discriminant analysis, chemometrics, mineral waters, mineral composition
Antimicrobial Activity and Chemical Composition of Two Experimental Gels Based on Essential Oils
LAURA MONICA DASCALU (RUSU), MARIOARA MOLDOVAN, DOINA PRODAN, IRINA CIOTLAUS, RAHELA CARPA, RAZVAN ENE, SAVA SORINA, RADU CHIFOR, MINDRA EUGENIA BADEA
In this study, the comparative testing of the antimicrobial efficacy of 2 experimental photosensitizers (PS-H; PS-T) based on natural compounds with a commercial one based on toluidine blue O (TBO) FotoSan® was performed, by antimicrobial tests with G- and G+ bacterial strains and through SEM microscopy on dental enamel, using LED phototherapy. For the formulation of the experimental natural photosensitizers we used Frankincense (T) and Thieves (H) essential oils (EO), used as photosensitizing agents in antimicrobial photodynamic therapy in the control of the microbial biofilm of the oral cavity. We also tested the composition of experimental photosensitizers by GC-MS chromatography. Our results suggest that EO should be further investigated as a promising source of natural compounds that can be used to combat bacterial strains. Essential oils can inhibit growth of a broad range of pathogens correlating to their presence in aromatic plants.
Keywords: GC-MS, SEM, antibacterial effect
Elemental Analysis of Culinary Herbs and Spices by ICP OES: Classification by Chemometrics
ALEKSANDRA N. PAVLOVIĆ, JELENA M. MRMOŠANIN, SNEŽANA Č. JOVANOVIĆ, SNEŽANA S. MITIĆ, SNEŽANA B. TOŠIĆ, JOVANA N. KRSTIĆ, GORDANA S. STOJANOVIĆ
The inductively coupled plasma optical emission spectrometry method (ICP OES) was optimized and validated for the quantification of 21 elements in 88 samples of 23 types of culinary herbs and spices. All analyzed samples were low in Na, but rich in Ca, K and P. Among the microelements, the most abundant was Fe, followed by Cu, Zn, Cr, and Se. The concentrations of toxic elements (Cd and Pb) were below the permissible limits given by the World Health Organisation (WHO). Chemometrics was performed by the principal component analysis (PCA) and cluster analysis (CA). PCA generated two principal components that explained 43.82% of the total variance in the data and all samples were classified into six groups based on the element content. Also, PCA and CA allowed the differentiation and classification of culinary herbs and spices based on the concentration of five major elements.
Keywords: culinary herbs, spices, macro and microelements, ICP OES, chemometrics, classification
The Comparative Overview of HPLC Analysis of Different Extracts from Morus Species from Southeast Serbia
DANICA DIMITRIJEVIĆ, DANIJELA KOSTIĆ, MILAN MITIĆ, DUŠAN PAUNOVIĆ, BRANKA STOJANOVIĆ, JOVANA KRSTIĆ, SLAVICA STEVANOVIĆ, JASMINA VELIČKOVIĆ
The aim of this work was to evaluate the content of phenolic compounds (phenols, flavonoids and anthocyanins) of Morus alba L. fruit (white mulberry), Morus rubra L. (red mulberry) and Morus nigra L. fruit (black mulberry) by the HPLC analysis. In the extracts of white, red and black mulberry identified the four phenolic acids by HPLC analysis: chlorogenic, 4-caffeoylquinic, 5- caffeoylquinic and caffeic acid. 5-caffeoylquinic acid was identified in all tested extracts of white, red and black mulberry. 4-caffeoylquinic acids contain all the extracts except methanol extract of red mulberry. Caffeic and chlorogenic acid containing methanol extracts of white and red mulberry.
Keywords: Morus species, HPLC analysis
Inverted Versus Direct Structure Bulk Heterojunction Organic Solar Cells Involving a Triphenylamine-Based Small Molecular Donor
GAVRIL-IONEL GIURGI, LORANT SZOLGA, ISTVAN KOVACS, ELENA BOGDAN, NICULINA DANIELA HӐDADE, ANAMARIA TEREC, ION GROSU, JEAN RONCALI
Bulk heterojunction solar cells involving a triphenylaminebased molecular donor and PC61BM with direct and inverted structures have been fabricated and optimized. The devices have been characterized under simulated solar illumination and the conversion efficiency and stability of the two kinds of organic solar cells are discussed.
Keywords: Organic solar cells, bulk heterojunction, inverted structure, molecular donors, triphenylamine derivatives
Amino-Substituted Porphyrins at the Border of Hybrid Materials Generation and Platinum Nanoparticles Detection
DIANA ANGHEL, MIHAELA BIRDEANU, ANCA LASCU, CAMELIA EPURAN, EUGENIA FAGADAR-COSMA
Two amino substituted porphyrins, namely: 5,10,15,20-tetrakis(4- aminophenyl)porphyrin (TAPP) and 5,10,15,20-tetrapyridyl-21H,23H-porphine (TPyP) have been used for complexation reaction of platinum nanoparticles (PtNPs) with the main purpose to recover or detect them from diluted leaching solutions, after transformation in colloidal solutions. The complexation reactions were monitored by UV-vis spectroscopy and revealed that both porphyrins have the capacity to complex PtNPs in different detection domains ranging from 2.776 to 40.457 x 10-6 M in the case of TAPP, and in a larger range of 8.07 x 10-6 – 7.03 x 10-5 M in the case of TPyP. Excellent correlation coefficients of 99.35 % and 99.57 % respectively have been obtained in each case. During complexation a nanomaterial based on TAPP and a micromaterial composed from TPyP both having as second partner PtNPs were obtained and thoroughly characterized by atomic force microscopy (AFM). The aggregation phenomena that occurred for each amino-porphyrin in DMF, in their acidified solutions and in their hybrid materials, revealed that the TAPP-PtNPs hybrid is a nanomaterial, based on triangular prisms aggregates of acidulated TAPP, and the TPyPPtNPs hybrid is a micromaterial that is based on pyramidal shaped aggregated from the acidulated solution of TPyP.
Keywords: amino-substituted porphyrins, PtNPs, Pt-NPs detection, UV-vis spectroscopy, AFM characterization
Spin Labelled Hemoglobin- Based Oxygen Carriers (HBOC): Preparation and Evaluation of In Vivo / In Vitro Stability
RADU SILAGHI-DUMITRESCU, CRISTINA GRUIAN, CRISTINA PUSCAS, ALEXANDRA SIMON, EVA FISHER-FODOR, VLAD AL. TOMA, ANCA FARCAS, IOANA ROMAN, VIOLETA-FLORINA SCURTU, AMR A.A. ATTIA, GRIGORE DAMIAN
Site-directed spin labeling and EPR characterization (continuous wave as well as DEER) of two blood substitute candidates is described for the first time: glutaraldehyde-polymerized bovine hemoglobin and the related hemoglobin-albumin copolymer. In vitro, with two different types of cell cultures, these spin-labeled candidates are relatively stable; however, they appear to be rapidly reduced in vivo, most likely via removal or reduction of the spin label (as opposed to removal of the blood substitute candidate from the circulatory system altogether).
Keywords: hemoglobin, albumin, blood substitute, HBOC, EPR, spin label, MTSSL, in vivo, cell culture, free radical/p>
Comparative Characterization of Somatic Hybrids of Solanum Bulbocastanum + S. Tuberosum Cv. ‘Rasant’ with Their Parents in Relation to Biochemical Responses to Wound Stress and Trichome Composition
DANIEL CRUCERIU, IMOLA ERDELY-MOLNAR, ZORITA DIACONEASA, ANTONIA MARIA MARGINEANU, ADRIANA AURORI, ELENA RAKOSY-TICAN
Potato production is severely affected worldwide due to its susceptibility to pathogens and pests. Solanum bulbocastanum, a potential source of resistance genes, is sexually incompatible with potato. Therefore, somatic hybridization is an alternative tool for enrichment of the potato resistance gene pool. Some important mechanisms involved in resistance are trichomes and various plant secondary metabolites. These resistance mechanisms were recorded in S. bulbocastanum, potato cv. ‘Rasant’ and two of their somatic hybrids with different chromosome numbers in order to evaluate the acquisition of these resistance traits by somatic hybridization. The foliar trichomes were characterized microscopically for morphology and density. Total polyphenolic (TPC) and flavonoid (TFC) content and antioxidant activity (AA) were quantified, both before and after mechanical wounding. Wounding increased TPC, TFC and AA in all tested genotypes. S. bulbocastanum was far superior for all parameters when compared with S. tuberosum cv. Rasant. The 1508/5 somatic hybrid proved to be similar to the wild species for trichome morphology and density, whereas it has intermediate phenotype for the TPC, TFC and AA compared to the genitors. Therefore, somatic hybridization proves to be a useful tool for resistance mechanisms transfer from a wild species to a somatic hybrid, the 1508/5 genotype being a good candidate for future use in pre-breeding programs.
Keywords: antioxidant activity, cytogenetic, flavonoids, polyphenols, somatic hybrids, trichomes
Radiocarbon Dating of Makuri Lê Boom, a Very Old African Baobab from Nyae Nyae, Namibia
ROXANA T. PATRUT, ADRIAN PATRUT, DEMETRA RAKOSY, LASZLO RAKOSY, DANIEL A. LÖWY, JENŐ BODIS, KARL F. VON REDEN
The article reports the AMS (accelerator mass spectrometry) radiocarbon dating results of Makuri Lê Boom, a very large African baobab from Nyae Nyae Conservancy, Namibia. The investigation of this superlative baobab shows that it consists of 12 independent stems of different dimensions, which belong to three generations. Makuri Lê boom has an open ring-shaped structure, a type of architecture which allows baobabs to reach very large sizes and old ages. The oldest sample has a radiocarbon date of 1602 ± 17 BP, which corresponds to a calibrated age of 1520 ± 35 calendar yr. By this value, Makuri Lê boom becomes one of the oldest dated baobabs and angiosperms with accurate dating results.
Keywords: AMS radiocarbon dating, Adansonia digitata, tropical trees, dendrochronology, age determination, multiple stems.
The Influence of V2O5 on Spectroscopic and Optical Properties of MgO-KPO3 Glasses Co-Doped with Ag2O
CRISTINA SOMESAN, LIVIU CALIN BOLUNDUT, LOREDANA OLAR, VASILE POP, LEONTIN DAVID
X-ray diffraction (XRD), Fourier transform infrared (FTIR), electron paramagnetic resonance (EPR), Ultraviolet-visible (UV-Vis) spectroscopies measurements have been employed to investigate the glasses from the (V2O5)x·(KPO3)80-x·(MgO)19·(Ag2O)1 (0 ≤ x ≤ 10 mol%) system. The studied glasses had a fixed MgO and Ag2O content of 19 mol% and 1 mol% respectively, and the V2O5:KPO3 ratio was varied. XRD data confirms the vitreous nature of the studied samples. EPR, UV-Vis and IR data confirm the presence of vanadium in multiple valence states.
Keywords: V2O5-MgO-KPO3 glasses, X-ray diffraction, FT-IR, EPR, UV-vis analysis
Characterization and Application of New Efficient Nanosorbent Fe2O3 Prepared by a Modified Low-Temperature Urea Method
MILJANA RADOVIĆ VUČIĆ, JELENA MITROVIĆ, MILOŠ KOSTIĆ, NENA VELINOV, SLOBODAN NAJDANOVIĆ, DANIJELA BOJIĆ, ALEKSANDAR BOJIĆ
In this work, low-cost non-conventional nanostructured Fe2O3 was produced by a modified low-temperature urea method (MLTUM-Fe2O3). Non-magnetic amorphous nanoparticle MLTUM-Fe2O3 with a bouquet like morphology is found to play as an effective sorbent media to remove textile dye Reactive Blue 19 from textile industries dye effluents over a wide range of pH. The nanoparticles were characterized by X-ray powder diffraction analysis (XRD), scanning electron microscopy (SEM), energy dispersive Xray spectroscopy (EDX), FTIR and TGA. The surface area was measured by Brunauer-Emmett-Teller (BET) analysis. SEM image reveals bouquet like morphology with average particle size about 50 nm. The maximum sorption capacity of the sorbent is found to be 271.00 mg g–1 for Reactive Blue 19 and the data fitted with different isotherm models. Study on sorption kinetics shows that sorption of Reactive Blue 19 onto iron oxide follows pseudosecond- order kinetic.
Keywords: Amorphous materials, Nanostructures, Iron oxide, Chemical synthesis, Thermogravimetric analysis (TGA), X-ray diffraction
Kinetics of Gliclazide after Single Dose Oral Administration of Gliclazide 60 Mg Modified Release Tablet
DIANA IOANA POP, ADRIANA MARCOVICI, MONICA OROIAN, ANAMARIA GHELDIU, LAURIAN VLASE
The current study aimed to establish and describe the basic pharmacokinetics of a single dose of gliclazide 60 mg modified release formulation manufactured by Ranbaxy Laboratories Limited, now Sun Pharmaceutical Industries Limited, India. Ten mathematical models were created for analyzing the experimental data resulted from two bioequivalence studies conducted at Clinical Pharmacology and Pharmacokinetics Department of Terapia S.A. Model discrimination was done using the Akaike index value and it was observed that model number 10 (M10) is the model that best describes the gliclazide disposition. This model has two compartments (peripheral and central), mixed order absorption process (1st and zero order kinetics) with a lag time of around 3 hrs and 1st order kinetics of elimination. Applying this model in Phoenix software version 6.3 (Pharsight Corp., Mountain view, CA, USA) the main pharmacokinetic parameters of gliclazide were also computed.
Keywords: gliclazide, compartmental pharmacokinetic analysis, bioequivalence clinical trials, best model
Effect of Agaricus Bisporus and Origanum Majorana L Extract on the Shelf-Life and Nutritional Properties of Pork Liver Pâté
DORIN TIBULCA, MELINDA FOGARASI, SONIA A. SOCACI, SZABOLCS FOGARASI, CARMEN POP, DAN SALAGEAN, MARIA TOFANĂ, DELIA MICHIU
The current study aimed to examine the effects of Agaricus bisporus and O. marjorana extract and their beneficial impact on the shelflife and nutritional changes occurring in pork liver pâté during storage time. Based on the obtained result, regarding the characterization of O. marjorana essential oil (OMEO) and mushroom powder, three types of pork liver pâté were formulated with different proportion of OMEO and mushroom powder and they were sensory evaluated using the 9-point hedonic test. In order to determine the stability during storage time, the selected sample and the control sample were sampled initially, after 30, 60, 90 and 120 days of storage than subjected to physicochemical (protein, fat, moisture, ash, total carbohydrates, and energy) evaluation.
Keywords: Agaricus bisporus, biochemical changes, essential oil, Origanum majorana L., pork liver pâté, sensory evaluation, volatile profile
EPR Fingerprinting and Antioxidant Response of Four Selected Plantago Species
ANCA D. FARCAȘ, CEZARA ZĂGREAN-TUZA, LAURIAN VLASE, ANA-MARIA GHELDIU, MARCEL PÂRVU, AUGUSTIN C. MOȚ
In this study we compare the phytochemical composition and antioxidant properties of four Plantago species (P. cornuti, P. lanceolata, P. major and P. media), in terms of radical scavenging ability and their reductive properties in corroboration with EPR spectroscopy profiling. We found that Plantago extracts possess very low prooxidant activity while being efficient radical scavengers and electron donors. P. media showed the strongest antioxidant activity from the four species investigated. The relative composition derived from the EPR spectra of the studied extracts was compared to the phytochemical composition determined by HPLC-MS analysis. Downhill Simplex algorithm simulation of EPR experimental signals revealed that all four Plantago extracts display luteolin and chlorogenic acid profiles, as well as quercetin glycosides, especially rutin. EPR spectroscopy appears to be a useful tool for discrimination of radical-based complex mixture, rendering it as an alternative method for predicting chemical behaviour, regardless of synergistic or antagonistic effects.
Keywords: Plantago, Antioxidants, EPR fingerprinting
High-Temperature Solid-State Synthesis of Mg-Doped ZrO2: Structural, Optical and Morphological Characterization
ANTONELA BERAR, MARIETA MUREȘAN-POP, LUCIAN BARBUTUDORAN, RÉKA BARABÁS, LILIANA BIZO
15 at% Mg-doped ZrO2 ceramic material was synthesized by solid-state reaction at 1600 ºC. Particle size analysis of raw materials mixture depicts the formation of a narrow particle size distribution (PSD) with a mean particle size of about 56 nm. The structural analysis confirms that the assynthesized Mg-doped ZrO2 product is of pure tetragonal phase (t-ZrO2) with a crystallite size of 55.76 nm. The UV–VIS diffuse reflectance spectrum (DRS) showed a maximum %R at 550 nm and the estimated optical bandgap was about 3.83 eV. The morphology of the sample examined by scanning electron microscopy (SEM) shows interconnected grains in the sintered ceramics. Moreover, EDX analyses confirm the presence of Mg, Zr, and O, with a homogenous distribution throughout the sample.
Keywords: Mg-doped ZrO2, solid-state reactions, XRPD, UV-VIS spectroscopy, SEM/EDX
Screen-Printed Electrodes Made on Stone Paper Substrate for Uric Acid Electrochemical Detection
CODRUTA VARODI, FLORINA POGACEAN, MARIN GHEORGHE, LUCIAN BARBU-TUDORAN, STELA PRUNEANU
Flexible screen-printed electrodes on stone paper substrate (HP) and modified with gold nanoparticles (HP-AuNPs) or AuNPs-poly-methylene blue (HP-AuNPs-PMB) were fabricated and morphologically investigated by SEM/EDS. The electrochemical properties of the new electrodes were studied by cyclic voltammetry (CV). The best electrocatalytic properties for uric acid detection were obtained with HP-AuNPs electrode: 0.16 μM Limit of Detection, 5x10-7- 10-4 M linear range and 20.7 mA/M sensitivity.
Keywords: uric acid detection, stone paper substrate, AuNPs modified electrodes
Characterization of Botswana Coal from Two Coal Fields: Mabesekwa and Mmamabula to Determine Its Coal Rank
MMOLOKI MAKOBA, TABOKA MOALOSI, PAUL S. AGACHI, EDISON MUZENDA, TIRIVAVIRI A. MAMVURA
Coal samples from two different coal fields: Mabesekwa and Mmamabula were collected (with six seams from each coal field) to characterize using X-Ray diffractometer (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FT-IR) spectroscopy. Proximate and ultimate analysis are also given. Clay minerals kaolinite, pyrite, dolomite, siderite and calcite, and quartz were discovered. Comparing measurements of C, VM, GCV, MC and FC obtained from the samples with literature, Botswana coal identifies as lignite grade A coal suitable for applications in coal gasification and ammonia based fertilisers due to its high volatile matter and high reactivity of char. The paper looks to use different methods to analyse Botswana coal and recommend its potential applications based on literature.
Keywords: Botswana coal, characterization, XRD, SEM, FT-IR, coal rank
Determination and Assessments of Physico-Chemical Parameters of the Water from Anthropo-Saline Lakes Located in the Protected Area “Salina Turda”, Romania
LILIANA RUS, SIMONA-ELENA AVRAM, VALER MICLE
It was carried out the monitoring of the qualitative parameters for the "Ocnei" and "Rotund" lakes located in the protected area “Salina Turda”, Romania, and as well it was made a comparative analysis of the results with previous determinations. It was determined the evolution of the physico-chemical parameters on 5 segments of depth. The monitoring was carried out within 2 measurement campaigns. It has been determined that the lakes tend to lose basicity and it was found that the heliotherm phenomenon represents a stable index in comparison with previous determinations.
Keywords: anthropo-saline lakes, water quality, physico-chemical parameters