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Impact of SBT impeller diameter on kinetics of copper sorption : diploma thesis
No full textU ovom diplomskom radu ispitan je utjecaj promjera radijalnog turbinskog miješala s četiri ravne lopatice (SBT miješalo) na proces sorpcije bakra na sintetskom zeolitu u kotlastom reaktoru, s i bez razbijala. Otopina bakra pripravljena otapanjem odgovarajuće mase Cu(NO 3 ) 2 u destiliranoj vodi. U eksperimentima je korišten sintetski zeolit NaX srednjeg promjera čestica 0,0765 mm. Ispitivanja su provedena pri stalnoj temperaturi (25 °C) suspenzije. Utjecaj promjera SBT miješala s četiri lopatice na kinetiku sorpcije ispitan je eksperimentima u kojima su korištena miješala različitih promjera (D/d T = 0,32; 0,46; 0,57; 0,68). Analiza dobivenih kinetičkih eksperimentalnih podataka primjenom Weber-Morrisovog i Blanchardovog modela pokazala je da difuzija ne utječe na ukupnu brzinu procesa, odnosno da ispitivana reakcija prati kinetiku drugoga reda u reaktoru s i bez razbijala virova. Rezultati ispitivanja pokazali su i da se povećanjem D/d T omjera i u reaktoru s i bez razbijala virova smanjuje utrošak snage miješanja.In this diploma thesis, the influence of the diameter of the straight blade turbine (SBT impeller) with four blades on the copper sorption process of synthetic zeolite in a batch reactor with and without baffles was investigated. A copper solution was prepared by dissolving an appropriate amount of Cu(NO 3 ) 2 in distilled water. Synthetic zeolite NaX with an average particle diameter of 0.0765 mm was used in all experiments. The experiments were carried out at a constant temperature (25 °C) of the suspension. The influence of the diameter of SBT impeller with four blades on the kinetics of sorption was investigated by using impellers with different diameters (D/d T = 0.32; 0.46; 0.57; 0.68). The analysis of the obtained experimental kinetic data using the Weber-Morris and Blanchard models showed that diffusion does not affect the overall rate of the process, i.e. that the studied reaction in the reactor with and without baffles follows second order kinetics. The experiments results also showed that by increasing the D/d T ratio in both the reactor with and without baffles, the consumption of mixing power is reduced
THE BINDING AFFINITY OF THE MIXED DIPHENYLANTHRACENE AND ESTHER DERIVATIVE OF CALIX(4)ARENE TOWARDS THE SELECTED ORGANIC COMPOUNDS : bachelor thesis
No full textS ciljem da se ispita kompleksacijski afinitet miješanog difenilantracenskog i esterskog derivata kaliksarena (5,11,17,23 tetra-tert-butil-25-(9,10-difenilantracen-2-iloksietoksi)-26,27,28- tris(etiloksikarbonilmetoksi)-kaliks[4]aren), K, prema odabranim organskim spojevima - rodaminu B, auraminu O i fluoresceinu te timokinonu, proveden je niz spektrofotometrijskih titracija u smjesi otapala acetonitril/diklormetan (φ = 0,5:0,5). Na temelju eksperimentalnih podataka dobivenih spektrofotometrijskim titracijama zaključeno je da ovaj kaliksarenski derivat od svih ispitivanih spojeva najveći afinitet pokazuje prema fluoresceinu pri čemu nastaje kompleks čija konstanta stabilnosti iznosi log (K [K-fluorescein] / mol dm -3 ) = 2,89 ± 0,01. S auraminom O i rodaminom B primijećeno je stvaranje intramolekulskih interakcija, međutim one su vrlo slabe i ne vode do stvaranja stabilnih kompleksa. Naposlijetku, za timokinon nije uočena nikakva interakcija sa spojem K. Razmatranjem strukturnih karakteristika ovih spojeva, zaključeno je da najveći doprinos stabilizaciji kompleksa imaju vodikove veze koje se uspostavljaju između molekule gosta i karbonilne skupine kaliksarena.To examine the complexation affinity of the mixed diphenylanthracene and esther derivative calixarene (5,11,17,23-tetra-tert-buthyl-25-(9,10-diphenylantracene-2-yloxyethoxy)-26,27,28-tris(ethyl- oxicarbomilmehtoxy)-kalix[4]aren), K, towards the selected organic compounds: rhodamine B, auramine O, thymoquinone and fluorescein, a series of spectrophotometric titrations were carried out in acetonitrile/diphenylantracene solvent mixture (φ = 0.5:0.5). Based on the experimental data obtained by spectrophotometric titrations it was concluded that out of all studied compounds this calixarene derivative shows the highest affinity towards fluorescein, whereby a complex, whose stability constant is log (K [K- fluoresceine] / mol dm -3 ) = 2.89 ± 0.01 is formed. The formation of intramolecular interactions was observed for auramine O and rhodamine B, however, these interactions were very weak and did not lead to the formation of a stable complexes. Finally, no interaction of compound K with thymoquinone was observed. Taking into consideration the structural characteristics of these compounds, it was concluded that the greatest contribution to the stabilization of the complexes is through hydrogen bonds established between the guest molecule and the carbonyl group of the calixarene derivative
Assurance and implementation of quality management system in wine production : bachelor thesis
No full textU ovom završnom radu cilj je bio opisati uspostavu sustava sigurnosti i kvalitete te implementacija HACCP sustava u proizvodnom pogonu za proizvodnju crnog vina. Opisana proizvodnja je tradicionalna te se temelji na stoljećima starim postulatima i sortama karakterističnim za dalmatinsko područje. Teoretski je opisana proizvodnja vina na tradicionalni način uz definiranje osnovnih principa HACCP sustava te sigurnosti i kvalitete hrane. Osnovna zadaća ovog rada bila je analiza opasnosti i određivanje kritičnih kontrolnih točaka (KKT). Kritične kontrolne točke određene su pomoću kreiranog dijagrama i analize potencijalnih opasnosti u svakoj fazi proizvodnje. Za proizvodni proces izrađen je HACCP plan za reguliranje utvrđenih kritičnih točaka kako bi se u konačnici dobio siguran i kvalitetan proizvod.In this bachelor thesis, the aim was to describe the establishment of the quality and safety system and the implementation of the HACCP system in the production plant for the production of red wine. Described production is traditional and is based on centuries-old postulates and varieties characteristic of the Dalmatian area. Theoretically is described wine production in the traditional way, along with defining the basic principles of the HACCP system and food safety and quality. The main task of this work was hazard analysis and determination of critical control points (CCP). Critical control points are determined using a created flow chart and analysis of potential hazards at each stage of production. For the production process, a HACCP plan was created to regulate the identified critical points in order to ultimately obtain a safe and high-quality product
Construction of solar cells based on TiO2 nanopowder and gel electrolyte : bachelor thesis
No full textU ovom radu je izrađeno osam solarnih ćelija s fotoosjetljivim bojilom kojima je mjeren fotoinducirani napon pri umjetnom osvjetljenju. Pripremljena su dva elektrolita, jedan tekući kod kojega su I 2 i KI otopljeni u etilen glikolu, a drugi je gel elektrolit pripravljen iz polietilen glikola. Svih osam stakalaca za izradu fotoanode koristi porozni sloj nanokristaličnog TiO 2 , koji je pripremljen kao pasta nanesena na vodljiva stakalca ''Blade'' metodom. Pasta je pripremljena iz nanopraha TiO 2 koji je suspendiran u razrijeđenoj octenoj kiselini i deioniziranoj vodi uz dodatak neionskog dispergenta Triton-X 100. Tanki slojevi nanokristaličnog oksida su obrađeni u laboratorijskom sušioniku, a zatim zagrijavani u laboratorijskoj peći. Četiri suha stakalca su pečena pri 400 °C, dok su ostala četiri pečena pri temperaturi 450 °C. Tako obrađena stakalca s nanoprahom uronjena su tijekom 24 sata u otopinu antocijanina, dobivenu iz sušenog cvijeta hibiskusa. Katoda solarne ćelije je pripremljena tako da je na osam stakalaca naprskavanjem nanesen vodljivi grafitni sloj koji je zatim sušen da bi isparilo organsko otapalo. Fotonaponske ćelije su sastavljene tako da su dvije ćelije obrađivane pri temperaturi 400 °C izrađene sa tekućim elektrolitom, a druge dvije s gel elektrolitom. Ostale četiri ćelije obrađivane pri temperaturi 450 °C su također sastavljene tako da dvije imaju tekući, a druge dvije gel elektrolit. Iz rezultata se može vidjeti da su ćelije koje su koristile gel elektrolit pokazale puno bolju dugotrajnost naspram ćelija s tekućim elektrolitom čak i s dodavanjem novih količina tekućeg elektrolita.In this paper, eight dye sentisized solar cells were made and their photo-induced voltage was measured under artificial lighting. Two electrolytes were prepared, one liquid in which I 2 and KI were dissolved in ethylene glycol, and the other a gel electrolyte prepared from polyethylene glycol. All eight cells of the photoanode use a porous layer of nanocrystalline TiO 2 , which was prepared as a paste applied to conductive slides using the "Blade" method. The paste was prepared using TiO 2 nanopowder that was dispersed in diluted acetic acid and deionized water with the addition of nonionic dispersant Triton-X 100. Thin layers of nanocrystalline oxide were processed in a laboratory dryer and then heated in a laboratory oven. Four dry glass slides were calcinated at 400 °C, while the other four were calcinated at a temperature of 450 °C. These thermally processed glass slides were immersed for 24 hours in an anthocyanin solution, obtained from dried hibiscus flower. The cathode of the solar cell was prepared by sputtering a conductive graphite layer onto eight glass slides, which were then dried so the organic solvent evaporates. Photovoltaic cells were assembled so that two cells processed at a temperature of 400 °C were made with liquid electrolyte, and the other two with gel electrolyte. The other four cells processed at a temperature of 450 °C were also assembled so that two had liquid and the other two gel electrolytes. From the results, it can be seen that the cells that used the gel electrolyte showed a much better longevity compared to the cells with the liquid electrolyte, even with the addition of new amounts of liquid electrolyte
Inhibitory effect of an extract obtained from cigarette waste on metal corrosion process : diplom athesis
No full textOpušci cigareta predstavljaju jedan od najprisutnijih oblika otpada na svijetu. Obzirom da je u brojnim studijama dokazana njihova ekotoksičnost javlja se potreba za njihovim recikliranjem. Jedan od načina na koji se ova vrsta otpada može reciklirati je njihova primjena kod inhibicije korozije. U ovom radu prikazani su rezultati ispitivanja utjecaja ekstrakata opušaka (ekstrakt ostataka duhana i ekstrakt filtera) na koroziju elektrode od Cu10Ni legure u 3,5 % – tnoj otopini NaCl, pH 8, pri temperaturama: 12 °C, 20 °C i 25 °C. Za procjenu djelotvornosti inhibicije provedena su elektrokemijska mjerenja (mjerenje potencijala otvorenog strujnog kruga, metoda linearne polarizacije, elektrokemijska impedancijska spektroskopija i potenciodinamička polarizacijska metoda) i analiza površine elektrode (FTIR analiza, SEM analiza i goniometrija). Elektrokemijska mjerenja pokazala su veću inhibicijsku djelotvornost za ekstrakt filtera u odnosu na ekstrakt ostataka duhana (pri svim temperaturama). Maksimalna učinkovitost inhibicije postignuta je modifikacijom površine elektrode s ekstraktom filtera pri 12 °C, a iznosila je 96 % (potenciodinamaička polarizacijska metoda), odnosno 88 % (elektrokemijska impedancijska spektroskopija). Analiza površine potvrdila je prisutnost ekstrakata opušaka na površini elektrode.Cigarette waste represent one of the most common forms of waste in the world. With the assessment that their ecotoxicity has been proven in numerous studies, there is a need for their recycling. One of the ways in which this type of waste can be recycled is their application in corrosion inhibition. This paper presents the results of testing the influence of cigarette waste extracts (tobacco residue extract and filter extract) on the corrosion of a Cu10Ni alloy electrode in a 3.5 % NaCl solution, pH 8, at temperatures: 12 °C, 20 °C and 25°C. To assess the effectiveness of inhibition, electrochemical measurements were carried out (measurement of the open circuit potential, linear polarization method, electrochemical impedance spectroscopy and potentiodynamic polarization method) and electrode surface analysis (FTIR analysis, SEM analysis and goniometry). Electrochemical measurements showed a higher inhibitory effectiveness of the filter extract compared to the tobacco residue extract (at all temperatures). The maximum inhibition efficiency was achieved by modifying the electrode surface with filter extract at 12 °C, and was 96 % (potentiodiamic polarization method) and 88 % (electrochemical impedance spectroscopy). Surface analysis confirmed the presence of cigarette waste extracts on the surface of the electrode
THE EFFECTS OF THE IONIC STRENGHT OF THE SUPPORTING MEDIA ON THE ELECTROCHEMICAL RESPONSE: GALIC ACID AT THE SINGLE WALL CARBON NANOTUBES ELECTRODE : diplom athesis
No full textProučavano je elektrokemijsko ponašanje galne kiseline na elektrodama od staklastog ugljika modificiranim jednozidnim ugljikovim nanocjevčicama, SWCNT (single-walled carbon nanotubes) u otopinama osnovnog elektrolita Britton-Robinson pufera, različite ionske jakosti, pri pH vrijednosti 3.6. Elektrokemijski fenomeni ispitivani su elektrokemijskim metodama: cikličkom voltametrijom i kronoamperometrijom. Dobiveni rezultati upućuju na to da je sveukupni proces, za realna vremena u kojima se provodi elektrokemijsko određivanje, većim dijelom pod kontrolom različitih difuzijskih procesa u samom poroznom sloju. Ovi procesi mogu se podijeliti na četiri podprocesa, ovisno o ionskoj jakosti osnovnog elektrolita. Na osnovu dobivenih rezultata, razjašnjeni su procesi koji utječu na oblik cikličkih voltamograma i to u svijetlu promijene brzine posmika, koncentracije galne kiseline te ionske jakosti osnovnog elektrolita. Ova razjašnjenja mogu biti korisna i za razjašnjenje drugih elektrokemijskih procesa koji se događaju u poroznim elektroaktivnim slojevima, ali i u razjašnjenju principa elektrokemijskog djelovanja („elektrokatalize“) ugljikovih nanomaterijala.The electrochemical behaviour of gallic acid was studied on glassy carbon electrodes modified with single-walled carbon nanotubes (SWCNTs) in Britton-Robinson buffer solutions of varying ionic strength at pH 3.6. The elucidation of electrochemical phenomena was carried out using electrochemical methods: cyclic voltammetry and chronoamperometry. The results obtained in this way indicate that the overall process, during real-time electrochemical determination, is largely controlled by different diffusion processes within the porous layer itself. These processes can be divided into four subprocesses depending on the ionic strength of the basic electrolyte. Based on the results obtained, the processes that control the appearance of cyclic voltammograms were explained, considering changes in scan rate, gallic acid concentration, and the ionic strength of the basic electrolyte. These explanations can be useful for understanding other electrochemical processes that occur in porous electroactive layers, as well as for elucidating the principles of the electrochemical action ("electrocatalysis") of carbon nanomaterials
Electrode fouling of single-walled carbon nanotube electrode during electrolysis of gallic acid and its prevention : diplom athesis
No full textPasivacija elektrode produktima elektrokemijske reakcije je fenomen koji može u velikoj mjeri utjecati na karakteristike elektrokemijskih senzora. Jedni od najpoznatijih spojeva koji pokazuju ovaj fenomen su fenoli. Zbog mnogih korištenih elektrokemijskih metoda za određivanje fenola, ali i zbog elektrodegradacije fenola u procesima pročišćavanja otpadnih voda, ovaj fenomen zahtjeva pomnija razmatranja u kontekstu pronalaženja metoda kojim bi se radne elektrode očistile od pasivacijskih produkata, čime bi se znatno smanjili troškovi održavanja postrojenja, vrijeme servisiranja postrojenja i produljio vijek trajanja elektroda. U ovom radu, proučeni su elektrokemijski fenomeni koji se javljaju pri oksidaciji galne kiseline na elektrodama modificiranim s ugljikovim nanocjevčicama. Koristeći cikličku voltametriju, prirode pojave, koje se odvijaju u poroznom sloju ugljikovih nanocjevčica, a koje su krucijalne za pasivaciju elektrode su objašnjene te je predložen kemijski/elektrokemijski tretman sloja koji uvelike može poboljšati reproducibilnost elektrokemijskog odziva, odnosno smanjiti pasivaciju elektrode.The passivation of electrodes by products of electrochemical reactions is a phenomenon that can significantly affect the characteristics of electrochemical sensors. Some of the most well-known compounds that exhibit this phenomenon are phenols. Due to the widespread use of electrochemical methods for the determination of phenols, as well as the electrodegradation of phenols in wastewater treatment processes, this phenomenon requires careful consideration in the context of finding methods to clean working electrodes from passivation products, thereby reducing the maintenance costs of facilities, downtime for servicing, and extending the lifespan of electrodes. In this study, electrochemical phenomena occurring during the oxidation of gallic acid on electrodes modified with carbon nanotubes were investigated. Using cyclic voltammetry, the nature of the processes occurring in the porous layer of carbon nanotubes, which are crucial for electrode passivation, was explained, and a chemical and electrochemical treatment of the layer was proposed that can significantly improve the reproducibility of the electrochemical response and reduce electrode passivation
Influence of impeller diameter on metastable zone width during sonocrystallization of borax by pulsed application of ultrasound irradiation : bachelor thesis
No full textIspitivanjene u ovom radu provedeno je u svrhu sagledavanja utjecaja promjera miješala na širinu metastabilne zone tijekom šaržne sonokristalizacije boraksa. Otopina dinatrijevog tetraborata dekahidrata zasićena na 30 °C kontrolirano se hladila brzinom od 6 °C h -1 do postizanja temperature od 15 °C. Istraživanje je provedeno u kristalizatoru laboratorijskog mjerila volumena 2,65 dm 3 . Tijekom procesnog vremena matična otopina je istodobno izložena djelovanju ultrazvuka (A = 20 %, P = 20 %) i mehaničkog miješanja. Mehaničkim miješanjem osigurano je stanje potpune suspenzije (N = N JS ). Za njegovu provedbu, korištena su turbinska miješala s ravnim lopaticama (SBT miješala) sljedećih promjera: D 1 /d T = 0,43; D 2 /d T = 0,53; D 3 /d T = 0,63. Temeljni cilj ovog rada bio je ispitati utjecaj promjera SBT miješala na kinetiku nukleacije boraksa. Kako bi se odredila kinetika nukleacije, bilo je potrebno odrediti koncentraciju matične otopine refraktometrijskom metodom te apsolutnu prezasićenost tijekom procesnog vremena pri svim ispitivanim procesnim uvjetima. Također, ispitivano je kako promjer miješala utječe na širinu metastabilne zone koja je određena općeprihvaćenom vizualnom metodom. Osim toga, upotreba Mersmannovog nukleacijskog kriterija omogućila je identifikaciju mehanizma kojim je nukleacija započela. Nadalje, na temelju snage privedene u sustavu, određen je promjer mikrovrtloga i procijenjen njegov utjecaj na širinu metastabilne zone. Rezultati dobiveni ispitivanjem ukazuju na to da povećanje promjera miješala rezultira višom maksimalnom prezasićenosti i širom metastabilnom zonom. Također, mehanizam kojim je nukleacija započela pri svim ispitivanim uvjetima odgovara primarnom heterogenom mehanizmu. Iako rezultati ispitivanja pokazuju kako se širina metastabilne zone sužava s promjerom mikrovrtloga, korelacija između tih dviju varijabli nije statistički značajna, stoga je za pouzdanije zaključke potrebno prikupiti veći broj podataka.The experiments in this study were conducted to assess the impact of impeller diameter on the metastable zone width during batch sonocrystallization of borax. A sodium tetraborate decahydrate solution saturated at 30 °C was gradually cooled at a rate of 6 °C h -1 until reaching a temperature of 15 °C. The research was carried out in a crystallizer of laboratory-scale volume of 2.65 dm 3 . Within the processing time, the mother liquor was simultaneously subjected to the action of ultrasound (A = 20 %, P = 20 %) and mechanical mixing. Mechanical mixing ensured a state of complete suspension (N = NJS). To achieve this, flat-blade turbine impellers (SBT impellers) of the following diameters were used: D 1 /d T = 0.43; D 2 /d T = 0.53; D 3 /d T = 0.63. The primary aim of this study was to investigate the influence of the SBT mixer diameter on nucleation kinetics. To achieve this, it was necessary to determine the concentration of the mother liquor using the refractometric method, as well as the absolute supersaturation during the process time under all examined process conditions. Furthermore, the influence of the impeller diameter on the metastable zone width, determined by a widely accepted visual method, was investigated. Additionally, the use of Mersmann's nucleation criterion enabled the identification of the mechanism by which the nucleation was initiated. Moreover, based on the power input into the system, the diameter of the microeddie was determined, and its impact on the width of the metastable zone was estimated. The results obtained from this investigation indicate that reducing the impeller diameter results in lower maximum supersaturation and a narrower metastable zone. Furthermore, the nucleation mechanism that initiated under all tested conditions corresponds to the primary heterogeneous mechanism. Although the results of the investigation show a reduction in the metastable zone width with decreasing microeddie diameter, the correlation between these two variables is not statistically significant, hence a larger dataset is required for more reliable conclusions
INVESTIGATION OF APPLICABILITY OF THE CONDUCTOMETRIC METHOD FOR MEASURING THE CONCENTRATION OF POTASSIUM SULFATE DURING THE BATCH COOLING CRYSTALLIZATION : bachelor thesis
No full textCilj ovog rada bio je ispitati primjenjivost konduktometrijske metode za mjerenja koncentracije kalijevog sulfata tijekom njegove kristalizacije hlađenjem. U prvom dijelu rada izrađene su baždarne krivulje, tj. prikazana je ovisnost električne provodnost, , o koncentraciji otopina kalijevog sulfata, c, u području od 0,40 do 0,72 mol dm -3 pri zadanim temperaturama, T, u području od 35 do 15 °C. Iz rezultata je uočeno da provodnost raste s porastom koncentracije i temperature otopine kalijevog sulfata. Kako bi se olakšala primjena ove metode te definirala ovisnost provodnosti o koncentraciji i temperaturi pristupilo se izradi korelacijske jednadžbe oblika: = K · c a ∙ T d . Eksponenti jednadžbe procijenjeni su metodom tzv. modificirane linearne regresije kojom se iz ovisnosti = k 1 · c a (tj. log = a logc + logk 1 ) odredila prvo vrijednost eksponenta a pri konstantnim vrijednostima temperature, a potom je definirana i vrijednost eksponenta d iz relacije = k 2 · T d , pri konstantnim vrijednostima koncentracije. Nakon određivanja vrijednosti eksponenata a i d, vrijednost konstante proporcionalnosti K određena je izjednačavanjem korelacijske jednadžbe s eksperimentalno izmjerenim vrijednostima provodnosti te je dobiven konačan oblik korelacijske jednadžbe: = 35,57 · c 0,8475 ∙ T 0,453 . Kako bi se odredila točnost i preciznost primijenjene metode, izvedena jednadžba je korištena za izračunavanje poznatih koncentracija otopina na temelju izmjerenih vrijednosti električne provodnosti i temperature. Ova ispitivanja su pokazala da je primijenjena konduktometrijska metoda uz korištenje izvedene baždarne jednadžbe umjereno točna. U drugom dijelu rada konduktometrijska metoda, uz primjenu korelacijske jednadžbe, je korištena za određivanje koncentracije otopine kalijevog sulfata tijekom njegove prekristalizacije iz matične otopine zasićene pri 30 °C hlađenjem do 15 °C. Iz dobivene krivulje procijenjeno je područje metastabilne zone te temperatura nukleacije koje blago odstupaju od one određene vizualno.The aim of this research was to examine the applicability of the conductometric method for measuring the concentration of potassium sulfate solution during crystallization by cooling. In the first part of the research, calibration curves, i.e. the dependence of the conductivity, , on the concentration of potassium sulfate solutions, c, in the range from 0.40 to 0.72 mol dm -3 at given temperatures, T, in the range from 35 to 15 °C were created. From the results, it was observed that the conductivity increases with the increase in the concentration and temperature of the potassium sulfate solution, and in order to facilitate the application of this method, a correlation equation was developed to express the dependence of the conductivity on the concentration and temperature of the form: = K · c a ∙ T d . The exponents of the equation were estimated using the so-called modified linear regression, which first determined the value of the exponent a from the dependence = k 1 · c a (log = a log c + log k 1 ) at constant temperature values, in the given temperature range, and then defined the value of the exponent d from the relation = k 2 · T d at constant concentration values in the given concentration range. After determining the value of the exponents aid, the value of the proportionality constant K was determined by equating the correlation equation with the experimentally measured conductivity values, which resulted in the final form of the equation: = 35.57 · c 0.8475 ∙ T 0.453 which indicates that the conductivity depends more on the concentration rather than temperature. In order to determine the accuracy and precision of the applied method, the derived equation was used to calculate the known concentrations of solutions based on the measured values of conductivity and temperature. These tests showed that the applied conductometric method with the use of the correlation equation is moderately reliable. In the second part of the research, the conductometric method with the application of the correlation equation, was used to determine the concentration of the potassium sulfate solution during its recrystallization from the mother solution saturated at 30 °C by cooling to 15 °C. From the obtained concentration curve, the region of the metastable zone and the nucleation temperature were estimated and those values slightly deviate from those determined visually
Aromatic profile of Lumblija : diploma thesis
No full textLumblija je hrvatski autohtoni pekarski proizvod koji se tradicionalno priprema za vrijeme katoličkog blagdana „Svi sveti“ na području otoka Korčule. To je 44. registrirani hrvatski proizvod koji je u studenom 2022. dobio europsku zaštićenu oznaku zemljopisnog podrijetla. Cilj ovog diplomskog rada je odrediti profil hlapljivih spojeva iz četiri uzorka Lumblije prikupljenih od lokanih proizvođača s otoka Korčule. Izolacija hlapljivih spojeva iz uzoraka Lumblije provedena je metodom mikroekstrakcije vršnih para na čvrstoj fazi (HS-SPME), a analiza izoliranih spojeva vezanim sustavom plinske kromatografije- spektrometrija masa (GC-MS). Identificirani hlapljivi spojevi potječu iz tri glavna izvora: hlapljivi spojevi nastali tijekom fermentacije tijesta, hlapljivi spojevi nastali tijekom pečenja tijesta te spojevi koji potječu od specifičnih dodataka. Identificirani spojevi pripadaju sljedećim kemijskim skupinama: terpeni, fenilpropanoidi, alkoholi, aldehidi, esteri, ketoni, aromatski ugljikovodici i kiseline. Među njima terpeni i fenilpropanoidi su bili najzastupljeniji spojevi. Na temelju dobivenih rezultata može se zaključiti kako se razlike u aromatičnom profilu među uzorcima mogu pripisati uglavnom dodacima poput začinskog i aromatičnog bilja. Dobiveni rezultati pokazuju kako karakterizacija hlapljivih aromatičnih sastojaka može biti vrlo koristan alat u cilju kontrole kvalitete i autentičnosti proizvoda.Lumblija is a Croatian autochthonous bakery product that is traditionally made during the Catholic holiday "All Saints" in the area of the island of Korčula. This is the 44 th registered Croatian product that received European Protected Geographical Indication (PGI) in November 2022. The aim of this thesis is to determine the profile of volatile compounds from four samples of Lumblija collected from local producers from the island of Korčula. Extraction of volatile compounds from Lumblija samples was carried out by the method of headspace solid phase microextraction (HS-SPME), and the analysis of isolated compounds by the gas chromatography-mass spectrometry bound system (GC-MS). Identified volatiles can be grouped in three main sources: volatiles from the fermentation of dough, volatiles from the baking process and volatiles characteristic for specific ingredients of product. Identified volatiles belong to different chemical classes: terpenes, phenylpropanoids, alcohols, aldehydes, esters, ketone, aromatic hydrocarbons and acids. Among them terpens and phenylpropanoids were the most numerous and the most abundant volatile compounds. According to the obtained results it can be seen that the most differences in aromatic profile can be attributed to some specific ingredients such as aromatic spices. Results from this study showed that characterization of volatile aromatic compounds could be effective tool in order to achieve product quality and authencity