Investigation of donepezil-hidrochloride stability using various analytical methods.

Predmet ove doktorske disertacije je proučavanje stabilnosti donepezilhidrohlorida, ispitivanjem razgradnih proizvoda nakon različitih uslova forsirane razgradnje. Stabilnost donepezil-hidrohlorida kako u čistom tako i u komercijalnom obliku je ispitivana sprovođenjem studije forsirane razgradnje. Uzorci za ispitivanje su radi toga bili podvrgnuti kiseloj i alkalnoj hidrolizi, oksidaciji i razgradnji pri zagrevanju kao i elektrohemijskoj razgradnji. Ispitivana je i elektrohemijska aktivnost donepezil-hidrohlorida u čistom obliku. Elektrohemijske reakcije su praćene pomoću različitih elektrohemijskih metoda (ciklične voltametrije i voltametrije sa pravougaonim impulsima) na elektrodi od zlata. Za analizu elektrolita u elektrohemijskim eksperimentima korišćene su i druge analitičke metode (HPLC, MS i NMR) radi potvrde podataka dobijenih elektrohemijskim ispitivanjima i objašnjenja procesa elektrohemijske oksidacije i predviđanja stabilnosti donepezil-hidrohlorida. Naučni cilj ovog rada je da se ispitivanjem stabilnosti odgovarajućim transformacijama donepezil-hidrohlorida razviju metode za kvalitativno i kvantitativno određivanje donepezil-hidrohlorida u rastvorima i da se analizom dobijenih rastvora nakon određenih reakcija forsirane razgradnje utvrdi priroda transformacija ispitivanog molekula. U tom cilju izvršena je karakterizacija dobijenih razgradnih proizvoda korišćenjem HPLC tehnika, IR i UV-Vis spektrofotometrije, LC-MS merenjima i 1D i 2D NMR spektroskopskih metoda. Proizvodi dobijeni oksidativnom razgradnjom koji su identifikovani predstavljaju proizvode metabolizma u ljudskom organizmu. Takođe, dobijeni eksperimentalni rezultati su upoređeni sa in-silico predviđenim razgradnim proizvodima uz pomoć softvera za predviđanje hemijskih reakcija. U ovom radu su ispitivani i razgradni proizvodi, koji se literaturno ne pominju u ranijim radovima kao razgradni proizvodi, a proizvodi su transformacije donepezila u oksidaciji u prisustvu oksidacionog sredstva i posebno proizvodi nastali elektrohemijskim transformacijama. Rezultati koji će proisteći iz istraživanja treba da doprinesu razvoju novih selektivnih, osetljivih, efikasnih, HPLC i elektrohemijskih metoda za kvalitativno i...The subject of this doctoral thesis is investigation of donepezil hydrochloride stability, by examination of the degradation products formed under different forced degradation conditions. The stability of donepezil hydrochloride both in pure form and in the commercial form is examined by conducting forced degradation studies. Samples were subjected to an acidic and alkaline hydrolysis, oxidation, degradation under thermal conditions as well as the electrochemical degradation. Electrochemical activity of donepezil hydrochloride in a pure form was also investigated. Electrochemical reactions are monitored using various electrochemical methods (cyclic voltammetry and square wave voltammetry) on a gold electrode. For the analysis of electrolytes in electrochemical experiments other analytical methods (HPLC, MS and NMR) were used to confirm the obtained data in electrochemical experiments, to evaluate the involved process of electrochemical oxidation and to predict donepezil hydrochloride stability. The scientific objective of this paper is to investigate the stability and transformations of donepezil hydrochloride involved in order to develop methods for qualitative and quantitative determination of donepezil hydrochloride in solutions and by analyzing the obtained solutions under a certain forced degradation conditions to determine the nature of the transformation of the tested molecule. In this intention the characterization of degradation products was performed using the HPLC technique, IR and UV-Vis spectrophotometry, LC-MS measurements and 1D and 2D NMR spectroscopic methods. Products obtained by the oxidative degradation which have been identified are products of metabolism in the human body. Also, the obtained experimental results were compared with in-silico predicted degradation products with the help of software for predicting chemical reactions. In this study, the degradation products were examined, which are not mentioned in the literature earlier works as degradation products, which are obtained by transformation of donepezil under oxidation conditions in the presence of an oxidizing agent or products of electrochemical transformations..

Numerical simulation of thermo-fluid properties and optimization of hot water storage tank in biomass heating systems

Za potrebe zagrevanja 1 ha plastenika na poljoprivrednom dobru u Padinskoj Skeli, koje se nalazi u okviru PKB korporacije, izgrađen je grejni sistem sa kotlom na biomasu, u kome se toplota dobija sagorevanjem balirane sojine slame. Zbog nestacionarnih efekata zagrevanja pojavila se potreba za uključivanjem akumulatora toplote u sistem grejanja. Ovaj rad ima za cilj numeričku i eksperimentalnu studiju izvršenu sa ciljem optimizacije akumulatora toplote u predmetnom grejnom sistemu, kao i optimizaciju celokupnog grejnog sistema. U akumulatoru toplote kapaciteta 100 m3, u kome se skladišti zagrejana voda, izvršena su merenja u 256 tačaka, kako u stacionarnom tako i u nestacionarnom režimu rada kotla. Analiza optimizacije je izvršena numeričkom simulacijom koja je obuhvatala i stacionarne i nestacionarne režime. Dobijeni rezultati pokazuju dobro poklapanje rezultata dobijenih eksperimentom i numeričkom simulacijom.A 1.5 MW combustion facility burning large bales of soy straw has been built for the purpose of heating 1 ha of vegetable greenhouses located within the complex of Agricultural Plant PKB in Padinska Skela, Serbia. The paper addresses numerical and experimental study of temperature distribution in a cylindrical, 100 m3 (8 m high, 4 m in diameter) hot water storage tank. The water tank optimization, as well as optimization of the heating facility as a whole, were identified as the main goals of the study performed. Water temperature was measured by a temperature probe inserted in the tank. Measurements were conducted in 256 measurement points, both under steady and unsteady water flow conditions. Water tank optimization analysis was carried out utilizing both steady and unsteady state numerical simulation. The results obtained indicated good agreement between the experimental and computational data acquired

Vertical temperature profile in the fluidized bed installation for combustion of waste fuels

Ovaj rad je prilog istraživanju sagorevanja čvrstih i tečnih otpadnih goriva. U tečna otpadna goriva čije odlaganje predstavlja ekološki problem ubrajamo talog iz rezervoara sirove nafte kao i korišćena jestiva/mineralna ulja i glicerin kao nus-produkt proizvodnje biodizela. Pored toga, ove materije, zbog neujednačenog sastava i gustine kao i visokog udela balasta, se ne mogu sagorevati u konvencionalnim ložištima, pa je tehnologija pogodna za njihovu toplotnu dezintegraciju fluidizovani sloj jer omogućava sagorevanje najrazličitijih vrsta goriva neuniformnog sastava. U čvrsta otpadna goriva ubrajamo i vanbilansne rezerve uglja (sitne granulacije, sa visokim sadržajem mineralnih materija i niskom toplotnom moći) koje je potrebno koristiti racionalnije, što opet podrazumeva primenu ložišta sa fluidizovanim slojem. U kotlovima sa fluidizovanim slojem mogu se sagorevati čvrsta goriva sa 85% inertnih materija, sa efikasnim odsumporavanjem dodavanjem krečnjaka direktno u ložište, sa niskom emisijom NOx, što ovoj tehnologiji daje značajnu prednost u poređenju sa drugim tehnologijama sagorevanja. U radu je dat opis eksperimentalne instalacije, kao i rezultat eksperimenata, sa naglaskom na raspodelu temperature po visini ložišta, u cilju određivanja zone intenzivnog sagorevanja u zavisnosti od karakteristika goriva.This paper is a contribution to the investigation of combustion of waste liquid and solid fuels. Waste liquid fuels include sediment from crude-fuel oil tanks or used edible/mineral oils, the disposal of which is most of ten linked to environmental issues. In addition, these substances, due to high ballast content, non-uniform composition and density, can not be burnt in conventional combustors, hence the technology of thermal disintegration in the fluidized bed (FB) imposes as a solution, which enables the combustion of fuels of most distinct types and non-uniform compositions. Waste solid fuels refer to coals from off-balance reserves (fine-grained, with high ballast and sulfur contents and low heating values) which should be used more rationally, implying the application of the FB combustion (FBC) as well. The fact that FB boilers can burn fuels with 85% of inert materials, with effective retention of SO2 by adding lime stone into the furnace, and with lower NOx emissions, gives FBC significant advantages, compared to other combustion technologies. Description of the experimental FBC facility is given, as well as experimental results, with the focus on the furnace temperature distribution, in order to determine the location of the intensive combustion zone as a function of fuel properties.

Vertical temperature profile in the fluidized bed installation for combustion of waste fuels

Ovaj rad je prilog istraživanju sagorevanja čvrstih i tečnih otpadnih goriva. U tečna otpadna goriva čije odlaganje predstavlja ekološki problem ubrajamo talog iz rezervoara sirove nafte kao i korišćena jestiva/mineralna ulja i glicerin kao nus-produkt proizvodnje biodizela. Pored toga, ove materije, zbog neujednačenog sastava i gustine kao i visokog udela balasta, se ne mogu sagorevati u konvencionalnim ložištima, pa je tehnologija pogodna za njihovu toplotnu dezintegraciju fluidizovani sloj jer omogućava sagorevanje najrazličitijih vrsta goriva neuniformnog sastava. U čvrsta otpadna goriva ubrajamo i vanbilansne rezerve uglja (sitne granulacije, sa visokim sadržajem mineralnih materija i niskom toplotnom moći) koje je potrebno koristiti racionalnije, što opet podrazumeva primenu ložišta sa fluidizovanim slojem. U kotlovima sa fluidizovanim slojem mogu se sagorevati čvrsta goriva sa 85% inertnih materija, sa efikasnim odsumporavanjem dodavanjem krečnjaka direktno u ložište, sa niskom emisijom NOx, što ovoj tehnologiji daje značajnu prednost u poređenju sa drugim tehnologijama sagorevanja. U radu je dat opis eksperimentalne instalacije, kao i rezultat eksperimenata, sa naglaskom na raspodelu temperature po visini ložišta, u cilju određivanja zone intenzivnog sagorevanja u zavisnosti od karakteristika goriva.This paper is a contribution to the investigation of combustion of waste liquid and solid fuels. Waste liquid fuels include sediment from crude-fuel oil tanks or used edible/mineral oils, the disposal of which is most of ten linked to environmental issues. In addition, these substances, due to high ballast content, non-uniform composition and density, can not be burnt in conventional combustors, hence the technology of thermal disintegration in the fluidized bed (FB) imposes as a solution, which enables the combustion of fuels of most distinct types and non-uniform compositions. Waste solid fuels refer to coals from off-balance reserves (fine-grained, with high ballast and sulfur contents and low heating values) which should be used more rationally, implying the application of the FB combustion (FBC) as well. The fact that FB boilers can burn fuels with 85% of inert materials, with effective retention of SO2 by adding lime stone into the furnace, and with lower NOx emissions, gives FBC significant advantages, compared to other combustion technologies. Description of the experimental FBC facility is given, as well as experimental results, with the focus on the furnace temperature distribution, in order to determine the location of the intensive combustion zone as a function of fuel properties.

Results of combustion of different waste fuel in fluidized bad

Održivi razvoj domaće energetike podrazumeva racionalno korišćenje energetskih resursa, upotrebu obnovljivih izvora energije i upravljanje otpadom uz zadovoljenje ekoloških propisa. Način za istovremeno ispunjavanje navedenih ciljeva je energetsko iskorišćenje niskovrednih, otpadnih materija, primenom tehnologije sagorevanja u fluidizovanom sloju (FS). U radu su prikazani rezultati eksperimenata sagorevanja više vrsta čvrstih i tečnih otpadnih materija, obavljeni na dvema instalacijama: industrijsko-demonstracionom (snage do 500 kW) i eksperimentalnom FS kotlu (snage do 100 kW). Mereno je temperatursko polje po visini ložišta, analiziran sastav dimnih gasova na izlazu iz ložišta i ostali parametri sagorevanja predmetnih goriva. Analizom dobijenih rezultata data je ocena njihove podobnosti sagorevanja u FS uz mogućnost iskorišćenja njihovog energetskog potencijala.The sustainable development of the national energy sector implies the rational use of energy resources, use of RES, and waste management with satisfying environmental regulations. A way to simultaneously fulfill the above objectives is the utilization of low-calorific and waste materials, applying the technology of fluidized bed combustion (FBC). This paper presents experimental results of combustion of number of solid and liquid wastes, conducted on two installations: industrial demonstration (capacity up to 100 kW) and experimental FB boiler (capacity up to 500 kW). The furnace temperature distribution, the composition of flue gas at the exit of furnace, and the other combustion parameters of the fuels are given. On the basis of these results, an evaluation of the waste fuels FB combustion and possibility of utilization of their energy potential is given

The experiments of fluidized bed combustion of diversely liquid fuel

Ovaj rad predstavlja doprinos ispitivanju sagorevanja alternativnih tečnih goriva poput: taloga iz rezervoara sirove nafte, zatim tečnih materija nastalih kao nusproizvod u procesima procesne, petrohemijske i metalurške industrije, iskorišćenih jestivih i mineralnih ulja, ili glicerina - nusprodukta proizvodnje biodizela. Ove materije se najčešće tretiraju kao otpadne ili istrošene materije i njihovo odlaganje/uklanjanje je najčešće skopčano sa velikim ekološkim problemima. Pored toga, te materije se zbog velikog sadržaja balasta, neujednačenog sastava i gustine ne mogu sagorevati u uobičajenim uređajima za sagorevanje tečnih goriva, pa se kao rešenje nameće tehnologija termičke dezintegracije u fluidizovanom sloju, koji omogućava sagorevanje materija najrazličitijeg porekla i neujednačenog sastava, uz smanjenje emisije polutanata i veliku termičku inertnost postrojenja. U radu je dat opis eksperimentalne instalacije za sagorevanje tečnih goriva velikih gustina u fluidizovanom sloju, kao i prikaz eksperimentalnih rezultata sagorevanja nekoliko tipova tečnih goriva sa i bez nečistoća, različitih gustina i viskoziteta, sa i bez dodavanja vode, u dugotrajnim, stacionarnim režimima. Prilikom analize eksperimenata akcenat je postavljen na efikasnost i stabilnost sagorevanja goriva različitog sastava. Razmatran je sadržaj štetnih produkata sagorevanja, uz analizu rasporeda temperatura u ložištu radi određivanja lokacije zone intenzivnog sagorevanja u zavisnosti od karakteristika goriva.This paper is a contribution to the investigation of combustion of alternative liquid fuels, such as: the sediment from crude-fuel oil tanks; liquid substances - by-products of processes in process, petrochemical and metallurgical industries; used edible and mineral oils; or glycerin - by-product of biodiesel production. These substances are most commonly treated as waste or used matter, and their disposal/removal is most often linked to considerable environmental problems. In addition to this, these substances, due to high content of ballast matter, non-uniform composition and density, can not be burnt in conventional liquid fuel combustors, hence the technology of thermal disintegration in the fluidized bed imposes as a solution, which enables the combustion of fuels of most distinct types and non-uniform compositions, together with diminishing pollutant emissions and high thermal inertia of the facility. In the paper, a description of the experimental set-up for the combustion of high density liquid fuels in the fluidized bed is given, as well as experimental results obtained by combustion of several liquid fuel types, with or without impurities, with different densities and viscosities, with or without adding water, in long-term, steady regimes. During the analysis of the experiments, the focus was set on the combustion efficiency and stability, for fuels of various compositions. The content of harmful combustion products has been considered, as well as the analysis of furnace temperature distribution, in order to determine the location of the intensive combustion zone as a function of fuel properties

Results of combustion of different waste fuel in fluidized bad

Održivi razvoj domaće energetike podrazumeva racionalno korišćenje energetskih resursa, upotrebu obnovljivih izvora energije i upravljanje otpadom uz zadovoljenje ekoloških propisa. Način za istovremeno ispunjavanje navedenih ciljeva je energetsko iskorišćenje niskovrednih, otpadnih materija, primenom tehnologije sagorevanja u fluidizovanom sloju (FS). U radu su prikazani rezultati eksperimenata sagorevanja više vrsta čvrstih i tečnih otpadnih materija, obavljeni na dvema instalacijama: industrijsko-demonstracionom (snage do 500 kW) i eksperimentalnom FS kotlu (snage do 100 kW). Mereno je temperatursko polje po visini ložišta, analiziran sastav dimnih gasova na izlazu iz ložišta i ostali parametri sagorevanja predmetnih goriva. Analizom dobijenih rezultata data je ocena njihove podobnosti sagorevanja u FS uz mogućnost iskorišćenja njihovog energetskog potencijala.The sustainable development of the national energy sector implies the rational use of energy resources, use of RES, and waste management with satisfying environmental regulations. A way to simultaneously fulfill the above objectives is the utilization of low-calorific and waste materials, applying the technology of fluidized bed combustion (FBC). This paper presents experimental results of combustion of number of solid and liquid wastes, conducted on two installations: industrial demonstration (capacity up to 100 kW) and experimental FB boiler (capacity up to 500 kW). The furnace temperature distribution, the composition of flue gas at the exit of furnace, and the other combustion parameters of the fuels are given. On the basis of these results, an evaluation of the waste fuels FB combustion and possibility of utilization of their energy potential is given

Određivanje klopidogrela voltametrijom sa pravouglim impulsima na elektrodi od zlata

The determination of clopidogrel, an antiplatelet agent, was performed at a gold electrode in pH 3.7 acetate buffer using cyclic voltammetry (CV) and square wave voltammetry (SWV). Each voltammogram was characterized by the well defined peak at approximately 1.0 V. The current of anodic stripping peak exhibited a linear dependence on the clopidogrel concentration in the range from 317.89 to 935.16 μg cm-3. The obtained linearity was applied to determine clopidogrel in the tablet form of the pharmaceutical preparation (Plavix®). The results were compared to the UV spectrophotometric and HPLC methods. .Klopidogrel je antitrombotski agens iz tijenopiridinske klase, koji se koristi za inhibiranje formiranja krvnih ugrušaka pri lečenju koronarne arterijske bolesti, periferne vaskularne bolesti, i cerebrovaskularne bolesti. Elektrohemijsko ponašanje klopidogrel standarda i kao sastojka tablete Plavix® je definisano cikličnom voltametrijom. Njihovo kvantitativno određivanje na elektrodi od zlata u acetatnom puferu, pH 3,7, urađeno je voltametrijom sa pravougaonim impulsima (SWV). Pokazano je obema tehnikama da je svaki voltamogram okarakterisan dobro definisanim strujnim vrhom na 1,0 V. Na osnovu linearne zavisnosti anodnih struja od koncentracije klopidogrel standarda određena je masa klopidogrela u Plavix® tableti. Dobijeni rezultati pokazuju da SWV tehnika može biti korišćena direktno, brzo i jednostavno za određivanje klopidogrela u tabletama. Rezultati dobijeni SWV voltametrijskom tehnikom su poređeni sa rezultatima analize klopidogrela UV spektrofotometrijom i tečnom hromatografijom sa visokim performansama. Analitički rezultati pokazuju da je masa aktivne supstance u tabletama Plavix® u okviru limita specifikovanog farmakopejom. To ukazuje da voltametrija sa pravougaonim impulsima može biti uspešna alternativa hromatografskim i spektrofotometrijskim metodama.

The combustion of biomass - The impact of its types and combustion technologies on the emission of nitrogen oxide

Harmonization of environmental protection and the growing energy needs of modern society promote the biomass application as a replacement for fossil fuels and a viable option to mitigate the greenhouse gas emissions. For domestic conditions this is particularly important as more than 60% of renewables belongs to biomass. Beside numerous benefits of using biomass for energy purposes, there are certain drawbacks, one of which is a possible high emission of NOx during the combustion of these fuels. The paper presents the results of the experiments with multiple biomass types (soybean straw, cornstalk, grain biomass, sunflower oil, glycerin and paper sludge), using different combustion technologies (fluidized bed and cigarette combustion), with emphasis on the emission of NOx in the exhaust gas. A presentation of the experimental installations is given, as well as an evaluation of the effects of the fuel composition, combustion regimes and technology on the NOx emissions. As the biomass combustion took place at temperatures low enough that thermal and prompt NOx can be neglected, the conclusion is the emissions of nitrogen oxides primarily depend on the biomass composition - it is increasing with the increase of the nitrogen content, and decreases with the increase of the char content which provides catalytic surface for NOx reduction by CO