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Potentiometric determination of fluoride in honey and wine : diploma thesis
No full textCilj istraţivanja bio je odrediti koncentraciju fluorida u razliĉitim vrstama meda i vina. Fluoridi su odreĊeni potenciometrijski korištenjem fluorid-ionsko selektivne elektrode primjenom metode standardnog dodatka. Ispitana je koncentracija fluorida kod 11 vrsta meda, 6 vrsta bijelog i 6 vrsta crnog vina. Masena koncentracija fluorida u medu kretala se od 30,01 do 118,01 µg fluorida/kg uzorka. Prosjeĉna masena koncentracija fluoridnih iona je 59,78 µg fluorida/kg uzorka u ispitivanim uzorcima. Masena koncentracija fluorida u crnim vinima kretala se od 297,92 do 371,0938 µg fluorida/mL uzorka. Masena koncentracija fluorida u bijelim vinima kretala se od 284,72 do 373,56 µg fluorida/mL uzorka. Rezultati su ispod maksimalno dopuštenih vrijednosti koju preporuĉuje MeĊunarodna organizacija za vino (OIV), a to je 1 mg/L.The aim of the research was to determine the concentration of fluoride in different sorts of wine and honey. Fluorides were potentiometrically determined through using a fluoride-ionic selective electrode and application of the standard addition method. The concentration of fluorides was tested in 11 sorts of honey, 6 sorts of white and 6 sorts of red wine. The mass concentration of fluorides in honey ranged from 30.01 to 118.01 μg of fluorides per kg of sample. The average mass concentration of fluoride ions in the tested samples was 59.78 µg of fluorides per kg of sample. The mass concentration of fluorides in red wines ranged from 297.92 to 371.0938 µg of fluorides per milliliter of sample. The mass concentration of fluorides in white wines fluctuated from 284.72 to 373.56 µg of fluorides per milliliter of sample. The results produced through this research are below the maximum allowed value of 1 mg/L, recommended by the International Organization of Vine and Wine (OIV)
Gravimetric methods of analysis : bachelor thesis
No full textCilj ovog rada je teorijsko razmatranje i eksperimentalna primjena gravimetrijskih metoda analize. Koncentracija nikla je određena gravimetrijskom metodom s taložnim reagensom dimetilglioksimom. Koncentracija kalcija je određena gravimetrijskom metodom taloženja iz homogene otopine uz oksalnu kiselinu kao taložni reagens. Koncentracija bakra određena je elektrogravimetrijski.The aim of this paper is the theoretical consideration and experimental verification of gravimetric methods of analysis. The nickel concentration was determined by the gravimetric precipitation method with the dimethylglyoxime as precipitating reagent. Calcium concentration was determined by gravimetric precipitation method from a homogeneous solution with oxalic acid as a precipitation reagent. The copper concentration was determined using electrogravimetric method of analysis
Corrosion behavior CuAlNi in 0,5 mol dm-3 H2SO4 solution : bachelor thesis
No full textU radu su prikazani rezultati ispitivanja korozijskog ponašanja CuAlNi legure (Al 10,4 %, Ni 4,1 %) u 0,5 mol dm -3 H 2 SO 4 otopini, pri temperaturama od 20 i 40 °C i brzinama miješanja elektrolita magnetskim miješalom od 150 i 450 o min -1 . Ispitivanja su provedena elektrokemijskim metodama: mjerenjem potencijala otvorenog strujnog kruga, metodom linearne polarizacije i potenciodinamičkom polarizacijskom metodom. Rezultati mjerenja pokazali su negativan utjecaj povišenja temperature i brzine miješanja elektrolita koji dovode do porasta gustoće korozijske struje i do smanjenja vrijednosti polarizacijskog otpora. Nakon polarizacijskih ispitivanja površine elektroda snimljene su optičkim mikroskopom. Snimke površine elektroda optičkim mikroskopom pokazale su prisutnost interkristalne korozije na površini legure.The results of the investigation of corrosion behavior of CuAlNI alloy (Al 10,4 wt. %, Ni 4,1 wt.%) in 0,5 mol dm -3 H 2 SO 4 solution, on temperatures of 20 and 40 °C and stirring with a magnetic stirrer with rates of 150 and 450 o min -1 , was presented. Investigations were performed by electrochemical methods: open circuit potential measurements, linear polarization method and potentiodynamic polarization method. The results of the measurements have shown negative impact of electrolyte temperature and stirring rate which is manifested by increase in corrosion current density and decrease in polarization resistance values. After polarization measurements, electrode surface was examined by light microscope. Images of electrode surfaces, obtained by light microscope, have shown the occurrence of intergranular corrosion on the alloy surface
Influence of temperature on aluminium passivation : bachelor thesis
No full textPrimjenom galvanostatske pulsne metode ispitani su mehanizam i kinetika rasta oksidnih filmova na aluminiju u otopini boratnog pufera (pH 7.8) različitih temperatura (10, 20 i 30 o C). Ustanovljeno je da se rast oksidnog filma na aluminiju odvija ionskom vodljivošću pod utjecajem jakog električnog polja kroz oksidni film, prema eksponencijalnom zakonu za ventilne metale (mehanizam “aproksimacije visokog polja”). Određeni su elektrokinetički parametri rasta oksidnog filma, ionska vodljivost i poluširina barijere, a dobivene vrijednosti opadaju s porastom temperature elektrolita. Nadalje, dobivene vrijednosti električnog polja, reda veličine MV cm -1 , opravdavaju primjenu modela “aproksimacije visokog polja” pri opisivanju rasta oksidnih filmova na aluminiju u otopini boratnog pufera različitih temperatura. Jakost električnog polja opada s porastom temperature.The mechanism and kinetics of growth of oxide films on aluminum in borate buffer solution (pH 7.8) of different temperatures (10, 20 and 30 o C) were investigated using the galvanostatic pulse method. It has been found that the growth of oxide film on aluminum takes place due to ionic conductivity under the influence of the high electric field through the oxide film according to an exponential law like on valve metals (“high field approximation” mechanism). Electrokinetic parameters of oxide film growth, ionic conductivity and half barrier width were determined, and the obtained values decreased with increasing electrolyte temperature. Furthermore, the values obtained for the electric field, of the order of magnitude of MV cm −1 , justify the application of the “high field approximation” mechanism to describe oxide film growth on aluminum in the borate buffer solution at different temperatures. The electric field strength decreases with increasing the temperature
Polyelectrolytes assembly for electrochemical sensing application by casting / coating methods : bachelor thesis
No full textRazvoj osjetilnih premaza, važnih elemenata senzora koji ujedinjuju funkcionalnost, jednostavnost, kemijsku i fizičku stabilnost, ima veliku ulogu u napretku elektrokemijskih senzorskih sustava. Zbog svoje raznolikosti i jednostavnosti korištenja polielektroliti su vrlo čest odabir u izradi elektrokemijskih osjetilnih slojeva. Polielektroliti se u strukturama elektrokemijskih senzora najčešće koriste za imobilizaciju raznih materijala u osjetilne slojeve. Ti materijali povećavaju osjetljivost, selektivnost te služe kao medijatori prijenosa elektrona između analita i pretvornika. Analitička izvedba može se značajno poboljšati sinergističkim učinkom materijala prisutnih u senzorskim strukturama. Strukture navedenih senzora mogu se postići primjenom raznih metoda, a jedna od poznatijih je metoda nakapavanja/ umakanja. Ovaj rad se temelji na primjeni metode nakapavanja/ umakanja u razvoju raznih slojeva i ulozi polielektrolita u tim strukturama.Development of sensing coatings, as important sensor elements that integrate functionality, simplicity, chemical and physical stability, has been shown to play a major role in electrochemical sensing system development trends. Simple and versatile assembling procedures and scalability make polyelectrolytes highly convenient for use in electrochemical sensing applications. Polyelectrolytes are mainly used in electrochemical sensor architectures for immobilization various materials into a sensing layer. These materials can often increase sensitivity, selectivity, electronic communication with the electrode substrate and can mediate electron transfer between an analyte and transducer. Analytical performance can be significantly improved by synergistic effect of materials present in these composites. As most reported methods for preparation of polyelectrolyte-based sensing layers are casting/coating methods. This bachelor thesis presents casting/coating methods in development of electrochemical sensors
Volatile compounds of black ash flowers (Fraxinus ornus L.) : bachelor thesis
No full textCrni jasen (Fraxinus ornus L.) je bjelogorično stablo ili grm iz porodice maslina, Oleaceae. U ovom završnom radu određen je sastav i sadržaj hlapljivih spojeva cvijeta crnog jasena. Za izolaciju hlapljivih spojeva korištena je vodena destilacija u modificiranoj aparaturi po Clevengeru i mikroekstrakcija vršnih para na čvrstoj fazi korištenjem različitih vlakna. Analiza svih uzoraka provedena je vezanim sustavom plinska kromatografija - spektrometrija masa na HP-5MS koloni. Glavni sastojci eteričnog ulja su ravnolančani zasićeni ugljikovodici dokosan (C 22 H 46 ) i trikosan (C 23 H 48 ). Glavni spoj dobiven mikroekstrakcijom vršnih para na oba vlakna bio je seskviterpen α-farnezen. Kvantitativno značajan spoj izoliran na sivom vlaknu je triterpenoid skvalen, dok je na plavom vlaknu pronađen ester etil- benzoat.Manna ash (Fraxinus ornus L.) is a deciduous tree or shrub from the olive family, Oleaceae. In this bachelor's thesis the composition and content of volatile compounds of manna ash flowers were determined. Hydrodistillation in modified Clevenger-apparatus and headspace solid phase microextraction (with various fibres) were used for the isolation of volatile compounds. Analysis of all samples was carried out by gas chromatography-mass spectrometry (GC/MS) on an HP-5MS column. The main constituents of essential oil were straight chained alkanes docosane (C 22 H 46 ) and tricosane (C 23 H 48 ). The main compound obtained by headspace microextraction was sesquiterpene α-farnesene on both fibres. Quantitatively significant compound isolated on the gray fiber, was the triterpenoid squalene, while on the blue fiber, the esther ethyl benzoate was found
Corrosion of iron under anaerobic conditions : bachelor thesis
No full textCilj ovog rada je razmatranje korozije željeza kao konstrukcijskog materijala i elektrokemijskih metoda kojima se može odrediti brzina korozije. Činjenica da željezo može lako zahrđati jedan je od velikih problema primjene ovog tehnički važnog metala i izaziva velike troškove u gospodarstvu. Da bi se spriječila korozija metala koriste se katodne i anodne elektrokemijske zaštite te zaštita inhibitorima i prevlakama. Korozija naftovoda se najčešće odvija u anaerobnim uvjetima, gdje se sulfat-reducirajuće bakterije smatraju glavnim krivcima mikrobiološke korozije. U radu je stoga posebno dat osvrt na ovu vrstu korozije, te na sam mehanizam korozije željeza kako u aerobnim tako i u anaerobnim uvjetima.The aim of this paper is to consider the corrosion of iron as a structural material and electrochemical methods by which the corrosion rate can be determined. The fact that iron can easily rust is one of the major problems of the application of this technically important metal and causes great costs in the economy. Cathodic and anodic electrochemical protections and protection with inhibitors and coatings are used to prevent metal corrosion. Oil pipeline corrosion most commonly occurs under anaerobic conditions, where sulfate-reducing bacteria are the main factor for microbiological corrosion. Therefore, this paper pays special attention to this type of corrosion, and to the mechanism of iron corrosion in both aerobic and anaerobic condition
Assessment of graphite film quality for DSSC by measuring surface resistance : diploma thesis
No full textU radu je ispitana površinska otpornost grafitnog vodljivog filma na staklenom supstratu namjenjenom za DSSC ćelije (eng. dye-sensitized solar cell). Površina 8 stakalaca (5 x 5 cm) za nanošenje grafitnog filma pripremljena je u sljedećem nizu: odmašćivanje, obrada koncentriranom sulfatnom kiselinom, ispiranje destiliranom vodom, ispiranje koncentriranim etanolom i sušenje. Na suhu površinu stakalaca nanesen je tanki sloj grafita sprej tehnikom do postizanja dobre pokrivenosti površine. Ispitana je električna otpornost i električna provodnost grafitnog filma pečenog pri 150, 200 i 250 °C u trajanju od 30 min. Radi usporedbe izmjerena je električna površinska otpornost i električna provodnost komercijalnih vodljivih stakalaca. Grafitni filmovi ispitani su mikroskopski pri različitim uvećanjima.In this paper the surface resistance of a conductive graphite film on a glass substrate intended for dye- sensitized solar cell - DSSC was analyzed. The surface of 8 glasses (5 x 5 cm) for applying the graphite film was prepared in the following sequence: degreasing, treatment with concentrated sulphuric acid, rinsing with distilled water, rinsing with concentrated ethanol and drying. A thin graphite film was sprayed onto the dry surface of the glasses to achieve good surface coverage. The surface resistance and electrical conductivity of graphite film heated to 150 °C, 200 °C and 250 °C for 30 min was tested. For comparison, the surface resistivity and electrical conductivity of commercial conductive glasses were measured. The graphite films were microscopically analyzed at available magnifications
Preparation of a graphite-based ion-selective sensor for determination of trihexyphenidyl hydrochloride : graduate thesis
No full textPripravljena je ion selektivna elektroda na bazi grafita uz dodatak ionsko asocijacijskog kompleksa (IAC) u određenim omjerima te je primijenjena na potenciometrijsko određivanje 3-heksifenidil hidroklorida (THPHCl) u koncentracijskom području od 3,16 ∙ 10 -6 do 3,16 ∙ 10 -3 M pri pH = 4,5. Pripravljeno je i testirano 11 membrana s različitim udjelima IAC i grafita. Najbolje odzivne karakteristike pokazale su membrane s udjelom od 20 odnosno 25 % IAC-a. Promjena potencijala po koncentracijskoj dekadi je 48,1 mV. Stabilan potencijal se uspostavlja u vremenu od jedne minute s negativnim pomakom s protekom vremena.A graphite-based ion-selective electrode was prepared with the addition of an ion association complex (IAC) in certain proportions and applied to the potentiometric determination of 3-hexyphenidyl hydrochloride (THPHCl) in a concentration range of 3.16 ∙ 10 -6 to 3.16 ∙ 10 - 3 M at pH = 4.5. Eleven membranes with different proportions of IAC and graphite were prepared and tested. Membranes with a 20 and 25% IAC, showed the best response characteristics. The change in potential per concentration decade is 48.1 mV. A stable potential is established in a time of one minute with a negative shift in the elapsed time
Selection of temperature transducers for measurements in batch reactor : bachelor thesis
No full textVođenje odnosno regulacija procesa predstavlja sastavni dio kemijskog inženjerstva, a temelji se na održavanju optimalnih uvjeta u procesu podešavanjem određenih procesnih veličina. Procesi se najčešće vode u reaktorima, destilacijskim kolonama, izmjenjivačima topline itd., pri čemu se najčešće reguliraju temperatura, protok, tlak i razina. Vođenje procesa može se prikazati regulacijskim krugom. Tri radnje se nužno odvijaju u regulacijskom krugu u kojem se proces vodi i to mjerenje, usporedba te podešavanje procesnih veličina. Ovaj rad temelji se na objašnjenu mjerenja koje se vrši pomoću mjernih pretvornika. Jedna od najčešće mjerenih procesnih veličina u industriji i laboratoriju je temperatura. Može se definirati kao mjera zagrijanosti tijela, odnosno preciznije kao mjera srednje kinetičke energije gibanja čestica i predstavlja jednu od osnovnih fizikalnih veličina. Za mjerenje temperature mogu se koristiti promjene tlaka, volumena, električnog otpora i drugih fizikalnih veličina koje su proporcionalne temperaturi. Mjerni pretvornici za mjerenje temperature mogu se općenito podijeliti na dilatacijske termometre, pirometre te električne termometre. Odabir pojedinog mjernog instrumenta ovisi o čimbenicima procesa i karakteristikama mjernih pretvornika. U ovom radu cilj je bio odabrati pogodne mjerne pretvornike za mjerenje temperature stijenke šaržnog reaktora i kapljevine koja se u njemu miješa vodeći se čimbenicima procesa i karakteristikama mjernih pretvornika. Pokazalo se da su za mjerenje temperature u šaržnom reaktoru najpogodniji električni termometri.Process control, represents a fundamental part of chemical engineering and is based on the maintenance of optimal conditions within the process through adjustment of certain process variables. Processes are most often controlled within reactors, distillation columns, heat exchangers etc. Most commonly controlled process variables in those processes are temperature, flow, pressure and level. Within a control loop, the actions of measurement, comparison and adjustment of process variables take place. This bachelor thesis is based on the explanation of measurement, which is carried out by using measuring instruments/devices. One of the most commonly measured process variables in industry and laboratories is temperature. It can be defined as a measure of heat of a certain object, or more precisely, as a measure of average kinetic energy of particle movement, and it represents one of the basic physical quantities. In order to measure temperature, changes in pressure, volume, electrical conductivity and other physical values which are proportional to temperature can be used. Measuring instruments for determining temperature can generally be divided into dilatation thermometers, pyrometers and electric thermometers. The selection of a particular measuring instrument depends on the process factors and the characteristics of the measuring transducer. In this bachelor thesis, the goal was to choose a suitable measuring transducer for the measurement of fluid temperature and wall temperature of a batch reactor, while being guided by the process factors and characteristics of the measuring transducers. It was shown that, for measuring temperature in a batch reactor, electric thermometers are most suitable