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Influence of impeller diameter on nucleation kinetics of sonocrystallization of borax : master thesis
No full textGlavni zadatak ovog rada bio je ispitati utjecaj promjera miješala u sustavu bez ultrazvučnog djelovanja (A=0 %) i u sustavu s ultrazvučnim djelovanjem (A=20 %) na kinetiku nukleacije boraksa u šaržnom kristalizatoru s kontroliranim hlađenjem. Za provedbu miješanja korištena su SBT miješala (engl. straight blade turbine) triju različitih promjera (D 1 =6,5 cm, D 2 =8,0 cm i D 3 =9,5 cm). Istraživanje je provedeno u kristalizatoru laboratorijskog mjerila volumena 2,65 dm 3 , pri čemu je matična otopina zasićena pri 30 °C, hlađena brzinom od 6 °C h -1 do temperature od 15 °C. U prvom dijelu ispitivanja provodila se kristalizacija uz mehaničko miješanje (A=0 %), dok se u drugom dijelu ispitivanja na matičnu otopinu djelovalo mehaničkim miješanjem i ultrazvučnim djelovanjem (A=20 %). U okviru ovog rada bilo je potrebno odrediti promjenu koncentracije matične otopine refraktometrijskom metodom, kao i promjenu apsolutne prezasićenosti tijekom procesnog vremena pri sva tri promjera miješala za oba ispitivana sustava. Također, analiziran je utjecaj promjera miješala na širinu metastabilne zone (ŠMSZ) te je primjenom Mersmannova nukleacijskog kriterija određen dominantni nukleacijski mehanizam. Rezultati su pokazali kako povećanje promjera miješala u sustavu bez ultrazvučnog djelovanja rezultira smanjenjem maksimalne prezasićenosti, odnosno širine metastabilne zone te brzine nukleacije. U sustavu s ultrazvučnim djelovanjem primijećeno je upravo suprotno. Kristalizacija je u svim ispitivanim slučajevima započela primarnim heterogenim mehanizmom. Primjenom granulometrijske analize metodom laserske difrakcije, sagledane su karakteristike finalnog produkta šaržne kristalizacije. Utvrđeno je da su kristali dobiveni u sustavu bez ultrazvučnog djelovanja značajno većeg srednjeg volumnog promjera i šire raspodjele od onih kristala dobivenih u sustavu s ultrazvučnim djelovanjem.The main task of this research was to examine the effect of impeller diameter on nucleation kinetics in systems with (A=20 %) and without (A=0 %) ultrasound irradiation on the kinetics of borax nucleation in a batch crystallizer. Three different diameters of SBT impeller were used (D 1 =6.5 cm, D 2 =8 cm and D 3 =9.5 cm). The research was carried out in a laboratory-scale crystallizer with a volume of 2.65 dm 3 , where the mother solution was saturated at 30 °C and then cooled at a rate of 6 °C h -1 to a temperature of 15 °C. In the first part of the research, only mechanical mixing (A=0 %) was carried out, while in the second part, mechanical mixing and ultrasound irradiation were simultaneously applied (A=20 %). It was necessary to determine the change of concentration of the mother solution using the refractometric method, as well as the change in the absolute supersaturation during processing time at all three impeller diameters in both investigated systems. Also, the influence of impeller diameter metastable zone width (MSZW) was analyzed and the dominant nucleation mechanism was determined by applying the Mersmann’s nucleation criterion. The results showed that the increase of impeller diameter in the system without ultrasound irradiation decreases the maximum supersaturation, MSZW as well as the nucleation rate. On the other hand, in the sonicated system, the opposite effect was observed. A primary heterogeneous mechanism initiated crystallization in all examined cases. Granulometric analysis of the product was conducted by using the laser diffraction method. It was found that the crystals obtained in silent system have a significantly larger mean volume diameter and a wider distribution than those obtained in the sonicated one
Copper ions sorption on milled peanut shells : bachelor thesis
No full textU ovom radu ispitivala se ravnoteža sorpcije bakrovih iona na osušenoj i usitnjenoj ljusci kikirikija na klasu čestica promjera između 100 i 200 µm. Eksperimenti su se provodili u pet šaržnih reaktora, u suspenzijama od po 1 g usitnjene ljuske kikirikija te 0,2 L otopine bakrovog(II) klorida dihidrata različitih početnih koncentracija. Pripremljene suspenzije miješane su u vodenoj kupelji s trešnjom pri izotermnim uvjetima (T = 27 °C) i brzini od 200 okr/min. Uzorci suspenzija su uzorkovani i analizirani UV/VIS spektrofotometrom u definiranim vremenskim intervalima tijekom 96 sati kako bi se u ispitivanom sustavu utvrdilo uspostavljanje ravnotežnog stanja. Dobiveni eksperimentalni podatci analizirani su Langmuirovom, Freundlichovom i Sipsovom izotermom. Analiza slaganja eksperimentalnih podataka s adsorpcijskim izotermama te vrijednosti izračunatog RMSE parametra pokazali su kako se Langmuirova izoterma najbolje slaže s eksperimentalnim podatcima te da se učinkovitost sorpcije smanjuje porastom početne koncentracije otopine bakrovog(II) klorida dihidrata. U svim ispitivanim sustavima ravnotežno stanje je postignuto nakon 24 sata; količina bakrovih iona vezanih u ravnoteži neovisna je o početnim koncentracijama otopina i iznosi oko 0,20 mmol/g, osim za najnižu korištenu koncentraciju.In this thesis, the equilibrium of copper ion sorption on dried and milled peanut shell particles with diameter between 100 and 200 µm was investigated. The experiments were carried out in five batch reactors, in suspensions of 1 g of milled peanut shells and 0.2 L of copper(II) chloride dihydrate solution of different initial concentrations. The prepared suspensions were mixed under isothermal conditions (T = 27 °C) and at a speed of 200 rpm. Suspension samples were sampled and analyzed with a UV/VIS spectrophotometer at defined time intervals during 96 hours to verify if an equilibrium state had been established in the systems investigated. The obtained experimental data were analyzed by Langmuir, Freundlich and Sips isotherms. The analysis of the agreement of the experimental data with the adsorption isotherms and the values of the calculated RMSE parameter revealed that the Langmuir isotherm shows the best agreement with the experimental data and that the sorption efficiency decreases with the initial concentration of the copper(II) chloride dihydrate increase. In all systems tested, equilibrium state was reached after 24 hours; the amount of copper ions retained on milled peanut shells in equilibrium is independent of the initial concentrations of the solutions and is about 0.20 mmol/g, except for the lowest concentration used
Effect of fluid flow on pressure drop in a porous layers : bachelor thesis
No full textPrilikom strujanja fluida kroz porozni sloj dolazi do gubitaka energije fluida uslijed površinskog trenja i oblika ĉestica koje formiraju taj sloj. Ukupan gubitak energije fluida manifestira se padom tlaka kojeg je moguće eksperimentalno i raĉunski odrediti. U ovom radu izvršena je karkterizacija triju poroznih slojeva ĉije se veliĉine ĉestica znaĉajno razlikuju. TakoĊer je sagledan utjecaj visine poroznog sloja i površinske brzina strujanja fluida na pad tlaka u sustavu. Dobivene eksperimentalne vrijednosti pada tlaka potom su usporeĊivane s onima odreĊenim teorijskim izrazima. Orijentaciona karakterizacija poroznog sloja može se izvršiti indirektnim naĉinom koristeći relativno jednostavno mjerljive karakteristike ispitivanog sloja. Eksperimentalnim ispitivanjima potvrĊeno je da se povećanjem visine poroznog sloja kao i povećanjem površinske brzine strujanja fluida pad tlaka u sustavu znatno povećava, tj. da dolazi do većih gubitaka energije fluida. Usporedbom teorijski i eksperimentalno odreĊenih vrijednosti pada tlaka najmanja odstupanja se uoĉavaju kod primjene Ergunove jednadžbe. To je posebno naglašeno kod poroznog sloja sastavljenog od najmanjih ispitivanih ĉestica (dĉ,ekv = 0,0025 m). MeĊutim, za konkretniji zakljuĉak sugeriraju se dodatna ispitivanja koja bi ukljuĉivala slojeve u većem rasponu veliĉina ĉestica.When fluid flows throught porous layer there are energy losess due to suface friction and resistance due to the shape of the particles which form that layer. The total loss of fluid energy is manifested by a pressure drop in the system, which can be determined experimentally and theoretically. In this work characterization of three porous layers whose particle sizes differ significantly was performed. The influence of the height of the porous layer and fluid superficial velocity on pressure drop in the system has been investigated as well. The experimental determined pressure drop were then compared with those obtained using theoretical expressions. The orientational characterization of the porous layer can be performed using the relatively easily measurable characteristics of the questioned porous layer. Experimental examinations have confirmed that increasing the height of the porous layer as well as increasing the fluid superficial velocity, the pressure drop in the system increases significantly. Comparing theoretically and experimentally determined values of pressure drop, the smallest deviations are observed when Ergun's equation has been applied. This is especially emphasized in the case of the porous layer composed of the smallest examined particles (dĉ,ekv = 0.0025 m). However, for more concrete conclusion, additional examinations of porous layers in a larger range of particle sizes are suggested
Inhibition of a-enzyme by essential oils from plants of lamiaceae families : bachelor thesis
No full textDanašnjim naĉinom ţivota iz dana u dan globalno raste prisutnost nekih ne zaraznih bolesti, kao što su Alzheimerova bolest, Diabetes mellitus i pretilost. Potreba za mjerama u borbi protiv ovih bolesti posljednih je godina, diljem svijeta, potakla povećan broj istraţivanja s ciljem otkrivanja novih prirodno prisutnih aktivnih spojeva sa svojstvima korisnim za ljudsko zdravlje. Usporavanje probave škroba inhibicijom enzima kao što je α-amilaza igra kljuĉnu ulogu u kontroli ove bolesti. Mnoga provedena istraţivanja potvrdila su hipoglikemijski uĉinak eteriĉnih ulja i sve ukupnu dobrobit na zdravlje. Cilj ovog rada je pregledati literaturu provedenih istraţivanja na temu eteriĉnih ulja biljaka porodice Lamiaceae koji djeluju kao inhibitori enzima α-amilaze, ĉije djelovanje moţe imati uĉinak kod osoba koje boluju od dijabetesa. S ovim ciljem su pregledana dostupna i relevantna znanstvena literatura; baze podataka Web of Science Core Collection i Scopus. Rezultati su pokazali da su eteriĉna ulja biljaka porodice Lamiaceae vaţan i znaĉajan izvor spojeva s inhibicijskim uĉinkom na enzim α-amilaza.With today's lifestyle, the presence of some non-communicable diseases, such as Alzheimer's disease, Diabetes mellitus and obesity, is increasing globally. The need for measures to combat these diseases has, in recent years, stimulated an increased number of researches with the aim of discovering new naturally occurring active compounds with properties beneficial to human health all over the world. Slowing down the digestion of starch by inhibiting enzymes such as α-amylase plays a key role in controlling this disease. Many studies have confirmed the hypoglycemic effect of essential oils and the overall health benefits. The aim of this paper is to review the literature of research conducted on the subject of essential oils of plants of the Lamiaceae family that act as inhibitors of the enzyme α-amylase, whose action can have an effect on people suffering from diabetes With this aim, the available and relevant scientific literature from Web of Science Core Collection and Scopus databases was reviewed. The results showed that the essential oils of plants of the Lamiaceae family are an important and significant source of compounds with an inhibitory effect on the α-amylase enzyme
Sea bittern as a potential source of MgO : bachelor thesis
No full textZbrinjavanje gorke morske vode od velike je važnosti za očuvanje ekosustava stoga se iznalaze razne metode za njeno iskorištavanje. Cilj rada je istražiti do sada primijenjene metode za iskorištavanja gorke morske vode kao potencijalnog izvora magnezijeva oksida visoke čistoće. Gorka morska voda nastaje kao nusproizvod prilikom proizvodnje NaCl iz morske vode djelovanjem sunčeve energije, te predstavlja koncentrirani oblik mnogih soli. Iz gorke morske vode primjenom inovativnih metoda mogu se dobiti elementi Na, Mg, Ca, K, Li, Rb, Pb, U, Zn. Njihova koncentracije u gorkoj morskoj vodi je 20-30 puta veća nego u svježoj morskoj vodi stoga gorka morska voda predstavlja alternativni izvor za proizvodnju magnezijeva oksida. Metodama eksploatacije magnezija iz gorke morske vode kao što su elektroliza, precipitacija, te primjenom novih tehnika želi se postići što veće iskorištenje gorke morske vode i dobivanja što čistijeg konačnog produkta MgO. Od posebne važnosti je metoda dvostruke soli koja predstavlja jednostavnu tehniku proizvodnje magnezijeva oksida visoke čistoće (MgO > 99%), kakav zahtjeva vatrostalna industrija.Disposal of sea bittern is of great importance for the preservation of the ecosystem, therefore various methods for its exploitation. The aim of the work is to investigate the methods applied so far for the exploitation of sea bittern as a potential source of high-purity magnesium oxide. Sea bittern is obtained as a by-product during the production of NaCl from seawater by the action of solar energy and is a concentrated form of many salts. The elements Na, Mg, Ca, K, Li, Rb, Pb, U, and Zn can be obtained from sea bittern using innovative methods. Their concentration in sea bittern is 20-30 times higher than in fresh seawater, therefore sea bittern represents an alternative source for the production of magnesium oxide. With the methods of magnesium exploitation from sea bittern as electrolysis, precipitation, and the example of new techniques, we want to achieve the greatest possible use of sea bittern and obtain the purest possible final product MgO. Of particular importance is the double salt method, which is a simple technique for the production of high-purity magnesium oxide (MgO > 99%) as required by the refractory industry
Corosion behaviour of stainless steel in seawater : master thesis
No full textUtjecaj temperature i koncentracije sulfidnih iona na korozijsko ponašanje nehrđajućih čelika 304L i 316L u morskoj vodi istraživan je različitim elektrokemijskim metodama. Tijekom istraživanja korištena su mjerenja potencijala otvorenog kruga, metode linearne i potenciodinamičke polarizacije. Utvrđeno je da se brzina korozije povećava s povećanjem temperature morske vode, a također i koncentracije sulfidnih iona. Analiza površine svjetlosnim mikroskopom i optičkim profilometrom nakon mjerenja potenciodinamičke polarizacije otkrila je da se broj i dubina jamica također povećavaju na isti način.The effect of temperature and concentration of sulphide ions on the corrosion behaviour of 304L and 316L stainless steels in seawater has been investigated by different electrochemical methods. Open circuit potential measurements, linear and potentiodynamic polarization methods have been employed during the investigation. It has been found that the corrosion rate increases with the seawater’s increasing temperature and the concentration of sulphide ions. Surface analysis with a light microscope and optical profilometer after potentiodynamic polarization measurements reveal that the number and depth of pits also increase in the same way
Modeling of microwave extraction of total phenolic and antioxidant activity of rosemary (Rosmarinus officinalis) : bachelor thesis
No full textPoznato je da ružmarin (Rosmarinus officinalis L.) predstavlja iznimno bogat izvor fenolnih spojeva, koji su zaslužni za njegovu visoku bioaktivnost. Posljednjih godina ova biljka se opsežno proučava kao izvor prirodnih bioaktivnih spojeva zbog snažnog antioksidativnog i protuupalnog djelovanja, antibakterijskih i antimutagenih svojstava te kao kemopreventivno sredstvo. U Dalmaciji, koja je od davnina bogata autohtonim ljekovitim biljkama, ružmarin je široko rasprostranjen. Nedovoljnim unosom antioksidansa ljudski organizam snosi posljedice. Tvdnja "Paradoks kisika" o kojoj će se u nastavku govoriti, objašnjava opasnost reaktivnih kisikovih vrsta za oblike života. Implementacija novih metoda ekstrakcije s većom iskoristivošću energije i sirovine i upotreba “zelenih“ otapala znatno doprinose očuvanju okoliša i energetskoj učinkovitosti. Voda, kao najvažnije otapalo u kombinaciji s mikrovalovima daje mnoge benefite za postizanje ovih ciljeva. Svrha ovog rada bila je optimirati parametre za ekstrakciju i naći najpogodnije uvjete za primjenu mikrovalne ekstrakcije. Nadalje, sljedeći zadatak bio je izvršiti karakterizaciju ekstrakata, odnosno odrediti ukupne fenole i antioksidacijsku aktivnost spektrofotometrijskim metodama. Na temelju rezultata uzoraka sa 7 različitih lokacija u Dalmaciji su izvedeni zaključci o utjecaju geografskog položaja, mikrolokacije i staništa biljke na navedena svojstva. Analizirajući podatke, uočava se da uzorci Makarske pokazuju visoke koncentracije ukupnih fenola i najveću antioksidacijsku aktivnost (1858,4 μM Fe 2+ ). Uzorak Milna (o. Brač) pokazuje najveći sadržaj ukupnih fenola (947,8 mg GAE/L). Uzorci Split (Kampus) i Sinj pokazuju nešto niže vrijednosti ukupnih fenola. Ekstrakcija potpomognuta mikrovalovima znatno utječe na svojstva ekstrakta. Neposredna blizina mora i višesatna izloženost suncu najvjerojatnije doprinose povećanju udjela bioaktivnih molekula. Time se može zaključiti kako su blizina mora i sunčeva svjetlost najvažniji čimbenici za visoku antioksidacijsku aktivnost ružmarina. Stoga ne čudi i podatak s početka ovog rada o podrijetlu imena, ružmarin, Rossamaris, što na latinskom jeziku znači morska rosa.Rosemary (Rosmarinus officinalis L.) is an extremely rich source of phenolic compounds, which are responsible for its high bioactivity. In recent years, this plant has been extensively studied as a source of natural bioactive compounds due to its strong antioxidant and anti-inflammatory effects, antibacterial and antimutagenic properties and chemopreventive action. In Dalmatia, which has been rich in autochthonous medicinal plants since ancient times, rosemary is very common. Insufficient intake of antioxidants has consequences for the human body. The phenomenon of the so-called "Oxygen Paradox", which is discussed below, explains the danger posed by reactive oxygen species to living organisms. The implementation of new extraction methods with higher energy and raw material utilization and the use of "green" solvents contribute significantly to environmental protection and energy efficiency. Water as the main solvent in combination with microwaves offers numerous advantages to achieve these goals.The aim of this work was to optimize the extraction parameters and to find the most suitable conditions for the application of microwave extraction. In addition, the next task was to characterize the extracts, i.e. to determine the total phenols and antioxidant activity using spectrophotometric methods. Based on the results from 7 different locations in Dalmatia, conclusions were drawn about the influence of the geographical location, the micro-location and the habitat of the plant on the aforementioned properties. The data analysis showed that the samples from Makarska had high concentrations of total phenols and the highest antioxidant activity (1858,4 μM Fe 2+ ). The sample from Milna (Brač) has the highest content of total phenols (947,8 mg GAE/L). The samples from Split (Kampus) and Sinj had slightly lower values of total phenols. Extraction assisted by microwaves significantly affects the properties of the extract.The close proximity to the sea and exposure to sunlight most likely contribute to an increase in the proportion of bioactive molecules. It can therefore be concluded that exposure to the sea and sunlight are the most important factors for the high antioxidant activity of rosemary. So, the information mentioned at the beginning about the origin of the name rosemary, Rossamaris, which is made up of the Latin words, is therefore not surprising
Development of rapid GC-MS/MS method for determination of eleven isothiocyanates and nitriles : diploma thesis
No full textIzotiocijanati i nitrili su razgradni produkti hidrolize glukozinolata, sekundarnih metabolita biljaka iz porodice kupusnjača. Izotiocijanati pokazuju biološku aktivnost zbog čega se razvijaju analitičke metode za njihovo određivanje. U ovom diplomskom radu razvijena je brza metoda za određivanje 3- fenilpropanonitrila, 2-feniletil-izotiocijanata, izopropil-izotiocijanata, alil-izotiocijanata, benzil- izotiocijanata, fenil-izotiocijanata, 3-(metiltio)propil-izotiocijanata, 2-metoksifenil-izotiocijanata, 3- metoksifenil-izotiocijanata i 4-metoksifenil-izotiocijanata. Spregnuta tehnika plinska kromatografija- tandemska spektrometrija masa (GC-MS/MS) korištena je za odjeljivanje odabranih izotiocijanta i nitrila iz smjese te njihovo kvalitativno i kvantitativno određivanje. Za pripremu početnih otopina korišteni su komercijalno dostupni standardi navedenih izotiocijanta i nitrila te heksan kao otapalo. Spektrometar masa s trostrukim kvadrupolom, u MRM načinu snimanja, korišten je za praćenje specifičnih reakcija prijelaza (kvantitativni i dva kvalitativna za svaki analit). Spektrometrija masa optimizirana je određivanjem energija sraza s dušikom za svaku specifičnu reakciju prijelaza. Plinska kromatografija optimizirana je promjenama temperaturnog programa. Za izradu krivulja umjeravanja odabran je raspon koncentracija od 0,0005 mg/mL do 0,5 mg/mL. Ispitani parametri vrednovanja: točnost, ponovljivost, linearnost, granica dokazivanja i granica određivanja pokazali su se zadovoljavajućima te je na taj način osigurana prikladnost brzog određivanja odabranih izotiocijanata i nitrila u smjesi.Isothiocyanates and nitriles are degradation products of glucosinolate hydrolysis, secondary metabolites found in plants form cabbage family. Isothiocyanates exhibit biological activity, which is why analytical methods are being developed for their determination. In this thesis, a rapid method for the determination of 3-phenylpropanonitrile, 2-phenylethyl isothiocyanate, isopropyl isothiocyanate, allyl isothiocyanate, benzyl isothiocyanate, phenyl isothiocyanate, 3-(methylthio)propyl isothiocyanate, 2- methoxyphenyl isothiocyanate, 3-methoxyphenyl isothiocyanate, and 4-methoxyphenyl isothiocyanate was developed. A hyphenated technique gas chromatography-tandem mass spectrometry (GC-MS/MS) was employed to separate the selected isothiocyanates and nitriles from the mixture and determine them qualitatively and quantitatively. Stock solutions were prepared from commercially available standards of these compounds using hexane as solvent. A triple quadrupole mass spectrometer, operated in multiple reaction monitoring (MRM) mode, was used to monitor specific transition reactions (quantitative and two qualitative transitions for each analyte). Mass spectrometry was optimized by determining nitrogen collision energies for each specific transition reaction. Gas chromatography was optimized by changing the temperature programme. Calibration curve range from 0.0005 mg/mL to 0.5 mg/mL was selected. Evaluated validation parameters including accuracy, repeatability, linearity, limit of detection, and limit of quantification were found to be satisfactory, ensuring the suitability of the rapid determination of selected isothiocyanates and nitriles in the mixture
Qualitative and quantitative determination of ascorbic and dehydroascorbic acid using UHPLC-MS/MS : diploma thesis
No full textAskorbinska kiselina ili vitamin C je jedan od najvažnijih i najpoznatijih vitamina neophodan za pravilno funkcioniranje ljudskog organizma te je poznati antioksidans. U izradi ovog diplomskog rada razvijena je metoda za kvalitativno i kvantitativno određivanje askorbinske kiseline (AA) te dehidroaskorbinske kiseline (DHA) kao njenog oksidacijskog produkta, a oba spoja se smatraju vitaminom C. U tu svrhu je korištena tekućinska kromatografija ultravisoke djelotvornosti povezana s detektorom masa s trostrukim kvadrupolom u negativnom načinu, snimanjem specifičnih prijelaza. Pritom su optimizirani po jedan kvantitativni i jedan kvalitativni prijelaz, redom, 175 → 115 m/z, 175 → 87 m/z za AA i 173 → 143 m/z, 173 → 71 m/z za DHA. Kao pokretna faza korištena je 0,1 % vodena otopina octene kiseline, dok je odjeljivanje učinjeno pomoću C18 kromatografske kolone pri temperaturi od 20 °C i protoku od 0,7 mL/min. Spektrometar masa je korišten s elektrosprej ionizacijom, temperature ionizatora 350 °C i napona kapilare -3600 V. Konstruirana krivulja umjeravanja je podijeljena u dva koncentracijska raspona od 0,5 µg/mL do 5,0 µg/mL te od 10 µg/mL do 50 µg/mL. Granice dokazivanja i određivanja su izračunane i omjera signala i šuma, i redom iznose, 2,1 ng/mL; 7,2 ng/mL za AA i 18,7 ng/mL; 62,3 ng/mL za DHA. Vrednovanjem točnosti, preciznosti, robusnosti metode te prikladnosti sustava i stabilnosti otopina radnog standarda (koja značajno opada tijekom 24 sata) potvrđena je prikladnost iste pri kvalitativnom i kvantitativnom određivanju AA i DHA.Ascorbic acid or vitamin C is one of the most important and well-known vitamins essential for proper functioning of the human body and it is a known antioxidant. In this thesis, a method was developed for qualitative and quantitative determination of ascorbic acid (AA) and dehydroascorbic acid (DHA) as its oxidation product; both compounds are considered as vitamin C. For this purpose, ultra-high performance liquid chromatography coupled with triple quadrupole mass detector was used in negative mode, by recording specific transitions. One quantitative and one qualitative transition were optimized, respectively, 175 → 115 m/z, 175 → 87 m/z for AA and 173 → 143 m/z, 173 → 71 m/z for DHA. A 0.1% aqueous solution of acetic acid was used as the mobile phase, while separation was performed using a C18 chromatographic column at a temperature of 20°C and a flow rate of 0.7 mL/min. Mass spectrometry was used with electrospray ionization, ionizer temperature of 350°C and capillary voltage of -3600 V. The calibration curve was divided into two concentration ranges, from 0.5 µg/mL to 5.0 µg/mL and from 10 µg/mL to 50 µg/mL. The limits of detection and quantification were calculated from the signal-to-noise ratio and are respectively 2.1 ng/mL; 7.2 ng/mL for AA and 18.7 ng/mL; 62.3 ng/mL for DHA. By validating the accuracy, precision, and method robustness, as well as system suitability and stability of working standard solutions (which significantly decreases over 24 hours), the method's suitability for qualitative and quantitative determination of AA and DHA was confirmed
Plasma physics and its role in nuclear fusion processes : bachelor thesis
No full textPlazma se najjednostavnije definira kao ionizirani plin. S obzirom da svaki plin ne može biti plazma, opisani su najvažniji fenomeni, uvjeti i fizikalne veličine koje karakteriziraju plazmu kao zasebno agregatno stanje. U usporedbi s postojećim energetskim izvorima, navodi se da nuklearna fuzija ima velike prednosti u kontekstu sigurnosti, zalihama goriva, ekološke prihvatljivosti i količini proizvedene energije. Reakcija deuterija i tricija trenutno se najviše istražuje za korištenje u prvim komercijalnim fuzijskim elektranama. S obzirom da Zemlja nema uvjete za postizanje nuklearne fuzije kao što imaju zvijezde, potrebno je plinove zagrijati na ekstremno visoke temperature prevodeći ih u stanje plazme koja se potom mora ograničiti u uređaju čiji materijal može podnijeti takve temperature dovoljno dugo da dođe do reakcije fuzije, a sve pri uvjetima da reakcija fuzije bude samoodrživa. Navedene su fizikalne veličine i uvjeti koje opisuju vjerojatnost postizanja reakcije fuzije, optimalni doprinos korisne proizvedene energije fuzijom te postizanje samoodržive fuzijske reakcije. Dvije glavne metode ograničavanja plazme su magnetsko i inercijalno s naglaskom na magnetsko ograničenje. ITER (eng. International Thermonuclear Experimental Reactor) je trenutno vodeći projekt izgradnje eksperimentalne električne elektrane na fuzijski pogon. Nasljedni projekt ITER-a se zove DEMO (eng. Demonstration power plant) s ciljem integracije svih rješenja opisanih izazova fuzije u industrijsku elektranu koja će nam omogućiti eksploataciju energije fuzije za svjetsku proizvodnju energije.Plasma is simply defined as an ionized gas. Since not every gas is plasma, the most important phenomena, conditions, and physical quantities that characterize plasma as a distinct state of matter are described. Compared to existing technology, nuclear fusion is argued to have significant advantages in terms of safety, fuel supply, environmental friendliness, and the amount of produced energy. The deuterium-tritium reaction is currently the most researched reaction to utilize in the first commercial fusion power plants. Since Earth does not have the conditions for achieving nuclear fusion like stars do, gases must be heated to extremely high temperatures, converting them into a plasma state that must then be confined within a device whose material can withstand such temperatures long enough for the fusion reaction to occur, all under the condition that the fusion reaction becomes self-sustaining. The physical quantities and conditions describing the probability of achieving fusion, the net produced fusion energy, and the self-sustaining fusion reaction are outlined. The two main methods of plasma confinement are magnetic and inertial, with an emphasis on magnetic confinement. ITER (abb. International Thermonuclear Experimental Reactor) is currently the leading project for the construction of an experimental fusion-powered electric plant. The successor project of ITER is called DEMO (abb. Demonstration power plant) with the aim of integrating all solutions to the described fusion challenges into an industrial power plant enabling us to exploit fusion energy for global energy production