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Qualitative and quantitative determination of selected isothiocyanates using GC-MS/MS : diploma thesis
No full textIzotiocijanati su razgradni produkti hidrolize glukozinolata, fitokemikalija koje se pretežno nalaze u biljkama iz porodice kupusnjača. Izotiocijanati su potencijalno biološki aktivni, zbog čega se razvijaju analitičke metode za njihovo određivanje. U ovom diplomskom radu razvijena je metoda za određivanje 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 iz smjese te njihovo kvalitativno i kvantitativno određivanje. Za pripremu otopina korišteni su standardi 2-, 3- i 4-metoksifenil-izotiocijanata te otapalo n-heksan. Plinska kromatografija optimizirana je promjenom brzine povećanja temperature peći (20 °C min -1 ). Spektrometar masa s trostrukim kvadrupolom, u MRM načinu snimanja, korišten je za praćenje specifičnih reakcija prijelaza (kvantitativni i dva kvalitativna za svaki spoj). Spektrometrija masa je optimizirana određivanjem energije sraza s dušikom za svaku specifičnu reakciju prijelaza. Prilikom izrade krivulje umjeravanja istraženi su različiti načini pripreme radnih otopina standarda (odabrano je klasično pipetiranje mehaničkim pipetama) te različita područja koncentracija otopina (odabran je raspon 2,5 μg mL -1 – 20,0 μg mL -1 ). Ispitani parametri vrednovanja: točnost, preciznost, specifičnost, linearnost, granica dokazivanja, granica određivanja i stabilnost, pokazali su se zadovoljavajućima. Metoda je uspješno primijenjena u analizi sintetskog uzorka poznate koncentracije. Navedenim je osigurana prikladnost metode za pojedinačno određivanje 2-, 3- i 4-metoksifenil-izotiocijanata u smjesi.Isothiocyanates are degradation products of glucosinolate hydrolysis. Glucosinolates are phytochemicals found mostly in plants from the cabbage family. Isothiocyanates are potentially biologically active, which is why methods for their determination are being developed. In this thesis, a method for the determination of 2-methoxyphenyl isothiocyanate, 3-methoxyphenyl isothiocyanate and 4-methoxyphenyl isothiocyanate was developed. Gas chromatography-tandem mass spectrometry (GC-MS/MS) was applied for the separation of selected isothiocyanates and qualitative and quantitative determination of separated compounds. Standards of 2-, 3- and 4-methoxyphenyl isothiocyanate and solvent n-hexane were used for the preparation of solutions. Gas chromatography was optimized by changing the oven temperature program rate (20 °C min -1 ). Triple quadrupole mass spectrometer, in MRM scan mode, was used for monitoring specific fragmentation reactions (quantifier and two qualifiers for each compound). Mass spectrometry was optimized by determination of the collision energy with nitrogen for each specific reaction of fragmentation. Different approaches of preparing the calibration curve working solutions were examined (forward pipetting with mechanical pipettes was selected) as well as different concentration ranges (range 2,5 μg mL -1 – 20,0 μg mL -1 was selected) were examined for making calibration curves. The validation parameters tested: accuracy, precision, specificity, linearity, the limit of detection, the limit of quantification and stability, were proven satisfactory. The method was successfully applied in the analysis of a synthetic sample of known concentration. This ensures the suitability of the method for the individual determination of 2-, 3- and 4-methoxyphenyl isothiocyanates in the mixture
IDENTIFICATION OF VOLATILE ORGANIC METABOLITES IN URINE OF PREGNANT WOMAN WITH PREECLAMPSIA : bachelor thesis
No full textRazličiti organizmi kao što su bakterije, plijesni i ljudi proizvode i oslobađaju relativno nepoznatu klasu metabolita. Ovi hlapljivi organski metaboliti skraćeno nazvani VOM (engl. Volatile organic metabolites) predstavljaju svojevrsni biosignal koji odražava zbroj svih utjecaja, uključujući genetiku, čimbenike okoliša, stanje prehrane i bolesti. Do sada su hlapljivi organski metaboliti kod ljudi otkriven u različitim tjelesnim medijima, kao na primjer u koži, u izdahnutom zraku, te u tjelesnim tekućinama kao što su slina, majčino mlijeko, znoj, krv i urin. Primjenom vezanog sustava plinske kromatografije i spektrometrije masa(GC-MS) uz prethodnu mikroekstrakciju na čvrstoj fazi određeni su hlapljivi metaboliti u uzorku urina trudnih žena s preeklampsijom. Za identifikaciju pojedinih metabolita korišteni su spektri masa i knjižnica spektara masa NIST. Od identificiranih metabolita naglasak je stavljen na one koji su povišeni kod oboljelih žena i potencijalni subiljezi za ovu bolest.Various organisms such as bacteria, molds and humans produce and release a relatively unknown class of metabolites. These volatile organic metabolites, abbreviated as VOMs (Volatile organc metabolites), are a kind of biosignal that reflects the number of all influences, including genetics, environmental factors, diet and disease. To date, volatile organic metabolites in humans have been detected in various bodily media, such as skin, exhaled air, and body fluids such as saliva, breast milk, sweat, blood, and urine. Using a coupled system of gas chromatography and mass spectrometry(GC-MS) with prior solid phase microextraction, volatile metabolites were determined in a urine sample of pregnant women with preclampsia. The NIST mass spectrum library was used to identify individual metabolites. Of the identified metabolites, emphasis is placed on those that are elevated in affected women and are potential markers for this disease
Effect of cooling rate on crystal growth of borax during sonocrystallization : master thesis
No full textU ovom radu ispitivano je kako brzina hlađenja matične otopine utječe na rast kristala dinatrijevog tetraborat dekahidrata (boraksa) tijekom sonokristalizacije. Ispitivanja su se provodila u šaržnom kristalizatoru laboratorijskog mjerila s pregradama i radijalnim turbinskim miješalom čija je brzina vrtnje bila jednaka potrebnoj za postizanje stanja potpune suspenzije kristala (N JS = 324 o min -1 ). Ultrazvučno djelovanje na otopinu provodilo se pomoću homogenizatora, frekvencije 24 kHz i snage 400 W, kontinuirano pri 20 % amplitudi. Kristalizacija se provodila iz matične otopine zasićene pri 30 °C hlađenjem do temperature od 10 °C pri brzinama od 4, 6, 8, 10 °C h -1 . Kako bi se dobio uvid u utjecaj ultrazvuka na navedeni proces također se provodila i kristalizacija bez njegovog djelovanja pri istovjetnim procesnim uvjetima (N JS = 324 o min -1 , T z = 30 °C) i brzini hlađenja od 6 °C h -1 . Tijekom eksperimenta, nakon nuleacije, provodila se analiza kristala u matičnoj otopini metodom laserske difrakcije te se istodobno određivala i koncentracija matične otopine refraktometrijskom metodom. Iz rezultata provedenih analiza sagledane su promjene raspodjele veličina kristala, srednjeg volumnog promjera kristala i njegove standardne devijacije te specifične površine kristala tijekom procesnog vremena pri svim ispitivanim uvjetima. Produkti kristalizacije pri navedenim procesnim uvjetima su također podvrgnuti granulometrijskoj analizi prosijavanjem te je analiziran i njihov oblik. Za sve ispitivane uvjete određen je i utrošak snage privedene sustavu tijekom miješanja i ultrazvučnog djelovanja. Iz rezultata je uočeno da se u procesu sonokristalizacije bez obzira na brzinu hlađenja matične otopine svojstva kristala ne mijenjaju bitno s obzirom na raspodjelu veličina i njihovu srednju veličinu. Najveći utjecaj brzine hlađenja odrazio se na promjenu specifične površine kristala koja je pak posljedica sekundarne nukleacije u sustavu. S druge strane, kad se usporede rezultati provedenih analiza u sustavima sa ultrazvukom sa sustavom bez ultrazvuka može se zaključiti da utjecaj ultrazvučnog djelovanja na svojstva kristala značajno nadmašuje utjecaj brzine hlađenja.In this work, the influence of the cooling rate of the mother liquor on the growth of crystals of disodium tetraborate decahydrate (borax) during sonocrystallization was studied. The test was carried out in a batch laboratory crystallizer equipped with a radial turbine with four blades whose rotation speed was equal to that required to achieve a state of complete crystal suspension (N JS = 324 rpm). Ultrasonic irradiation of the solution was carried out with a homogenizer with a frequency of 24 kHz and a power of 400 W, continuously at 20% of the amplitude. Crystallization was carried out from a mother liquor saturated at 30 °C by cooling to a temperature of 10 °C at rates of 4, 6, 8, 10 °C h -1 . In order to gain insight into the influence of ultrasound on the process, crystallization was performed without ultrasound, under the same process conditions (N JS = 324 rpm, Tz = 30 °C) at a cooling rate of 6 °C h -1 . During the experiment, after nucleation, crystals in the mother liquor were analyzed by laser diffraction method and at the same time, concentration of the mother liquor was determined using the refractometric method. Changes were observed in crystal size distribution, mean volume diameter of the crystals and its standard deviation, as well as the specific surface area of the crystals during process time. The obtained products were subjected to sieve analysis, and the shape of the crystals was also analyzed. For all investigated process conditions, the power supplied to the systems by mixing and ultrasonic radiation was determined. From the results, it was observed that during the sonocrystallization process, regardless of the cooling rate of the mother liquor, the properties of the crystals do not change significantly with regard to the size distribution and their average size. The greatest influence of the cooling rate was reflected on the change in the crystal specific surface area, which is a consequence of secondary nucleation in the systems. On the other hand, comparing the results obtained in systems with and without ultrasound, it can be concluded that the influence of ultrasound on crystal properties significantly exceeds the influence of the cooling rate
Corrosion behavioer of stainless steels in pfosphate buffer saline solution : master thesis
No full textPraćenjem vremenske promjene potencijala otvorenog strujnog kruga, primjenom linearne i cikličke polarizacije te elektrokemijske impedancijske spektroskopije ispitana je anodna i spontana korozija različitih vrsta nehrđajućeg čelika (AISI 304L, AISI 316L i 2205 DSS) u slanoj otopini fosfatnog pufera (PBS, pH = 7.4) pri 37 °C (tj. simuliranoj fiziološkoj otopini u ljudskom organizmu). Nakon anodne i spontane korozije, površine ispitivanih uzoraka snimljene su pomoću svjetlosnog i pretražnog elektronskog mikroskopa (SEM) uz EDS analizu. Utvrđeno je da otpornost materijala prema anodnoj koroziji raste redom: AISI 304L AISI 316L 2205 DSS. Naime, istim se redom povećava mogućnost repaivacije i otpornost na lokalnu koroziju. Korozijska otpornost uzoraka čelika na potencijalu otvorenog strujnog kruga posljedica je formiranja prirodnog oksidnog filma dvoslojne strukture, koji se sastoji od unutarnjeg barijernog i vanjskog poroznog sloja. Unutarnji barijerni sloj je jako tanak velikog otpora, dok je vanjski porozni sloj deblji i znatno manjeg otpora. Koroziju uzoraka čelika sprječava unutarnji barijerni sloj i to redom: AISI 304L < AISI 316L < 2205DSS. Svjetlosni mikroskop i SEM/EDS analiza nakon anodne i spontane korozije pokazuju oštećenja na AISI 304L i AISI 316L površini, dok je površina 2205 DSS čelika uglavnom neoštećena korozijom.Anodic and spontaneous corrosion of different types of stainless steel (AISI 304L, AISI 316L and 2205 DSS) in phosphate-buffered saline solution (PBS, pH = 7.4) at 37 °C (i.e., in simulated physiological solution in the human body) were examined using open circuit potential measurements, linear and cyclic polarization, and electrochemical impedance spectroscopy methods. After the anodic and spontaneous corrosion, the surface of the tested samples was investigated by light and scanning electron microscopy (SEM) with EDS analysis. It has been established that the anodic corrosion resistance of the examined materials inecreases in the order: AISI 304L < AISI 316L < 2205 DSS. Namely, the possibility of repassivation and the resistance to local corrosion increases in the same order. The corrosion resistance of steel samples at open circuit potential is a consequence of forming a natural oxide film with a bi-layer structure and consists of an inner barrier and an outer porous layers. The inner barrier layer has a small thickness and extremely high resistance, while the outer porous layer is much thicker but also has significantly lower resistance. The inner barrier layer mainly prevents corrosion of examined steel samples in order: AISI 304L < AISI 316L < 2205 DSS. Light microscopy and SEM/EDS analysis after anodic and spontaneous corrosion showed damage on the AISI 304L and AISI 316L surface, while the surface of 2205 DSS was almost undamaged by corrosion
Precipitation of Mg(OH)2 from a sea bittern after NaCl extraction : bachelor thesis
No full textIspitivanja su provedena u svrhu iskorištavanja gorke morske vode za dobivanje visokokvalitetnog magnezijeva hidroksida, tj. magnezijeva hidroksida u obliku praha visoke čistoće i što manjih dimenzija čestica. Korištena gorka morska voda uzorkovana je u Solani Ramova s lokacije Krvavica (Makarska). Ispitivanja su provedena na uzorcima magnezijeva hidroksida u obliku mulja i praha. Magnezijev hidroksid u obliku praha pripremljen je s promjenom temperatura radi proučavanja utjecaja temperature na veličinu čestica dobivenog taloga. Rezultati kemijskog sastava s obzirom na Mg i Ca ukazuju na visoki postotak MgO (97,47 %) u uzorku dok je sadržaj CaO (2,89%) znatno manji. EDS analiza potvrđuje visoku čistoću dobivenog praha magnezijevog hidroksida. Analiza raspodjele veličina čestica određena je prije (mulj) i poslije sušenja (prah) uzoraka metodom raspršenja laserskog svjetla u području od 20 nm do 2 mm. Uzorci su analizirani bez i uz primjenu ultrazvuka u trajanju od 100 s neposredno prije mjerenja u svrhu razbijanja aglomerata. Srednja veličina čestica mulja magnezijeva hidroksida je 3,082 µm. Vidljivo je odstupanje raspodjele veličina čestica u uzorcima praha bez (11,482 µm) i s povišenjem temperature (6,607 µm). Morfologija praha magnezijevog hidroksida potvrđuje nastanak ljuspičastih i nitastih struktura nepravilnih oblika (debljine do 400 nm) aglomeriranih u puno veće tvorevine (veličine µm). Nitaste strukture smanjuju se do 100 nm u uzorku praha s primjenom temperature.In this work sea bittern was used in order to obtain a high quality precipitate of magnesium hydroxide, i.e. magnesium hydroxide in the form of a high purity powder with a particle size as small as possible. Used sea bittern water was sampled at Solana Ramova from the Krvavica (Makarska). The investigations were carried out on magnesium hydroxide samples in the form of sludge and powder. Magnesium hydroxide in powder form was prepared with a temperature change to investigate the influence of temperature on the particle size of the precipitation obtained. The results of the chemical composition in terms of Mg and Ca indicate a high percentage of MgO (97.47%) in the sample, while the CaO content (2.89%) was significantly lower. The EDS analysis confirms the high purity of the magnesium hydroxide powder obtained. The analysis of the mean particle size distribution was determined before (sludge) and after drying (powder) of the samples by the laser light scattering method in the range of 20 nm to 2 mm. For the purpose of agglomerate reduction, the samples were analyzed immediately before the measurement for 100 s without and with ultrasound. The mean particle size of magnesium hydroxide sludge is 3.082 µm. The deviation of the particle size distribution in powder samples without (11.482 µm) and with temperature increase (6.607 µm) is visible. The morphology of magnesium hydroxide powder confirms the formation of flaky and filamentous structures of irregular shape (up to 400 nm thickness) agglomerated into much larger structures (µm). The filamentous structures are reduced to 100 nm in the powder sample by applying the temperature
Wettability of thin films with ZnO nanowires : bachelor thesis
No full textOpisana je teorija kvašenja standardnih materijala, kao i mogućnosti kontrole stupnja kvašenja strukturiranjem površine. Vodoprivlačnost i vodoodbojnost su izmjerene na površinama filmova s nasumično orijentiranim i vertikalno poredanim ZnO nanožicama, naraslim putem istog hidrotermalnog postupka, ali na različitim predslojevima s klicama ZnO nanočestica. Morfologija predslojeva i nanožica analizirana je pretražnom elektronskom mikroskopijom i mjerenjima difrakcije rentgenskih zraka pri malom kutu upada. Utvrđena je korelacija između izmjerenih kutova kvašenja i ukupne morfologije uzoraka, koja definira hrapavost njihove površine. Pokazano je da se visok stupanj vodoodbojnosti može postići s 1D nanostrukturama, podešavanjem detalja njihove morfologije i prostornog uređenja.Wettability theory is described as well as the possibilities of wettability control. Hydrophilicity and hydrophobicity were measured on surfaces of films with randomly oriented and vertically ordered ZnO nanowires, grown by the same hydrothermal process, but on different seed layers. The morphology of seed layers and nanowires was analyzed by scanning electron microscopy and grazing incidence X-ray diffraction measurements. The correlation was estimated between the measured wetting angles and the overall sample morphology that defines the surface roughness. A high degree of hydrophobicity was achieved using 1D nanostructures, solely by adjusting their morphology and alignment
Impact of the turbine impeller blade angle on copper adsorption on zeolite : diploma thesis
No full textU ovom radu ispitan je utjecaj nagiba lopatica turbinskog miješala na adsorpciju bakra na zeolitu i utrošak snage miješanja pri stalnoj temperaturi suspenzije. Za pripremu otopine koja sadrži Cu 2+ ione koristio se Cu(NO 3 ) 2 ∙3H 2 O. Kao adsorbens koristio se zeolit NaX ĉestica veliĉine od 0,063 do 0,090 mm. Eksperiment se proveo u šaržnom reaktoru s razbijalima virova. Kako bi se sagledao utjecaj nagiba lopatica turbinskog miješala na kinetiku adsorpcije, provedeni su eksperimenti s turbinskim miješalom s ĉetiri lopatice ĉiji je nagib varirao od 30° do 90°. Da reakcija prati kinetiku drugoga reda pokazala je izvršena kinetiĉka analiza eksperimentalnih podataka Ritchievim i Weber-Morrisovim modelom. Dobiveno je vrlo dobro slaganje dobivenih podataka s Ritchievim modelom. Rezultati ispitivanja pokazali su i da se povećanjem nagiba lopatica turbinskog miješala smanjuje utrošak snage miješanja.In this work, the impact of the turbine impeller blade angle on the copper adsorption on zeolite and the power consumption at a constant suspension temperature was investigated. Cu(NO 3 ) 2 ∙3H 2 O was used to prepare solutions containing Cu 2+ ions. Zeolite NaX particles with a size of 0.063 to 0.090 mm are used as an adsorbent. The experiment was conducted in a batch reactor with baffles. An influence of impeller blade angle on adsorption kinetics has been investigated using four-blade turbine, whose angle was varied from 30° to 90°. Kinetic analysis of the experimental data, by the Ritchie and Weber-Morris model, showed that the reaction follows the kinetics of the second order. It was, also, found that by increasing the turbine impeller blade angle the power consumption decreases
Removal of lead from an aqueous solution on different biosorbents - influence of particle size : bachelor thesis
No full textGlobalnim razvojem i povećanjem broja stanovnika dolazi do onečišćenja voda različitim štetnim tvarima, posebice teškim metalima. Takve vode su neuporabljive za ljudsku potrošnju jer mogu uzrokovati brojne ekološke i zdravstvene probleme. Postoje različite metode obrade voda onečišćenih teškim metalima, a njihov glavni nedostatak je visoka cijena. Iz toga su razloga istraživanja usmjerena na pronalaženje prirodnih, lako dostupnih materijala koji imaju mogućnost vezivanja teških metala, a ekonomski su i ekološki prihvatljivi. U ovom završnom radu provedeno je uklanjanje olova iz vodene otopine šaržnim postupkom na biosorbensima (koštice maslina, pelet komine maslina, ostaci hridinskog ježinca, koštice višnje i koštice trešnje) različitih veličina čestica (0,56-1,00 mm; 0,09-0,56 mm i 0,045-0,09 mm) prikupljenima u lokalnim pogonima za proizvodnju i preradu hrane. Za sve ispitane biosorbense učinkovitost uklanjanja olova povećava se smanjenjem veličine čestica zbog veće aktivne površine, ukazujući na adsorpciju kao glavni mehanizam vezivanja olova. Najbolju učinkovitost od 62,8% pokazale su koštice višnje, zatim 44,4% koštice trešnje, 29,6% ostaci hridinskog ježinca te 27,5%. koštice maslina, dok je za pelet komine maslina dobivena najmanja učinkovitost od 16,8%. Zbog visoke početne koncentracije olova od 2,705 mmol/L (≈ 560 mg/L) teško je bilo za očekivati postizanje konačne koncentracije ispod maksimalno dopuštene vrijednosti od 0,5 mg/L. Nižu ostatnu koncentraciju olova možda bi bilo moguće postići višestupanjskim šaržnim postupkom s novim obrocima biosorbenasa, za što su potrebna dodatna ispitivanja. Unatoč tome, čvrsti otpad i nusproizvodi iz poljoprivredno-prehrambenog sektora mogu biti korisni materijali za uklanjanje teških metala iz onečišćenih voda. Osim što bi pridonijeli smanjenju troškova obrade voda, smanjila bi se i količina otpada koji se neiskorišten nekontrolirano odlaže u okoliš.Global development and population growth lead to increasing water pollution by various harmful substances, especially by heavy metals. Such waters are unusable for human consumption and can cause numerous environmental and health problems. There are different methods for treatment of waters contaminated with heavy metals, and their main disadvantage is the high cost. For this reason, researches are focused on finding natural, easy available economically and environmentally friendly materials with ability of binding different heavy metals. In this final thesis, the removal of lead from an aqueous solution on biosorbents (olive pits, olive pomace pellets, remains of the sea urchin, sour cherry pits and cherry pits) of different particle sizes (0.56-1.00 mm; 0.09-0.56 mm and 0.045-0.09 mm) by batch method was performed. The biosorbents were collected in local food production and processing plants. For all tested biosorbents, the efficiency of lead removal increases by decreasing the particle size due to the higher surface area, pointing on the adsorption as the main removal mechanism. The best efficiency of 62.8% was achieved by sour cherry pits, then 44.4% for cherry pits, 29.6% for the remains of the sea urchin and 27.5% for the olive pits, while for the olive pomace pellet the lowest efficiency of 16.8% was achieved. Due to the high initial lead concentration of 2.705 mmol/L (≈ 560 mg/L), it was difficult to expect the final lead concentration below the maximum permissible value of 0.5 mg/L. Lower remaining lead concentration might be possible to achieve by multi-stage batch process with fresh biosorbents, but this requires further experiments. Nevertheless, solid waste and by-products from food production and processing can be useful materials for removal of heavy metals from polluted waters. Except the contribution in reduction of water treatment costs, the amount of uncontrolled disposal of unused waste into the environment could also be reduced
Phenolic profile and biological potential of white wine vinification by-products : bachelor thesis
No full textPreradom grožđa i postupkom vinifikacije zaostaju vrijedni nusproizvodi sa visokim sadržajem fenola koji posjeduju brojna pozitivna biološka svojstva, osobito antioksidacijsku i antimikrobnu aktivnost. Nusproizvod kao što je vinski talog pokazao se bogatim izvorom vlakana i fenola što omogućava njegovo korištenje u prehrani. U ovom radu su ispitana dva uzorka taloga prikupljena tijekom proizvodnje bijelog vina, nakon maceracije i prije fermentacije te nakon provedene hladne fermentacije. Određeni su ukupni fenoli metodom po Folin-Ciocalteu, fenolni profil HPLC (eng. High performance liquid chromatography) metodom te je ispitana antioksidacijska aktivnost FRAP (eng. Ferric reducing antioxidant power), ORAC (eng. Oxygen radical apsorbance capacity) i DPPH (eng. 2,2-diphenyl-1-picrylhydrazyl free radical scavenging) metodom. Rezultati ispitivanja pokazuju izuzetno visok udio fenola te raznolik fenolni profil ekstrakata. Osim fenolnog sastava uzorci su pokazali i dobru antioksidacijsku aktivnost. Iako su oba uzorka imala iznenađujuće dobre rezultate, posebno se ističe talog bijelog vina nakon maceracije obzirom da je imao gotovo dvostruko veći udio fenola kao i dvostruko bolju antioksidacijsku aktivnost u odnosu na talog vina uzorkovan nakon provedene fermentacije.After the grape processing and vinification, valuable by-products with a high phenolic content and numerous positive biological properties, especially antioxidant and antimicrobial activity remain. A by-product such as wine lees is a rich source of fibers and phenolics, which enables its use in nutrition. In this paper, two lees samples were collected during the production of white wine, one after maceration and before fermentation and other after cold fermentation. Total phenols were determined using the Folin- Ciocalte method, the phenolic profile by HPLC (High Performance Liquid Chromatography) method, and the antioxidant activity by FRAP (Ferric reducing antioxidant power) ORAC (Oxygen radical absorbance capacity) and DPPH (2,2-diphenyl-1-picrylhydrazyl free radical scavenging) method. The obtained results show an extremely high proportion of phenolics and diverse phenolic profile of the extracts. In addition to the phenolic composition, samples also showed good antioxidant activity. Although both samples had surprisingly good results, the lees after maceration stand out especially since it had almost twice higher amount of phenolics as well as two-fold higher antioxidant activity compared to the lees of white wine
Influence of the impeller diameter on the granulometric properties of borax crystals during crystallization with and without ultrasound irradiation : diploma thesis
No full textCilj ovog rada bio je ispitati utjecaj veličine miješala u kristalizatoru sa i bez ultrazvučnog djelovanja na rast kristala boraksa tijekom šaržne kristalizacije pri kritičnoj brzini vrtnje miješala (N = N JS ). Kristalizacija se provodila u kristalizatoru laboratorijskog mjerila, hlađenjem matične otopine zasićene pri 30 °C do temperature od 15 °C, brzinom od 6 °C h -1 . U radu je korišteno radijalno turbinsko miješalo s četiri ravne lopatice (tzv. SBT miješalo), a kako bi se sagledao utjecaj njegove veličine na granulometrijske karakteristike kristala ispitivanja su se provodila pri tri različita promjera miješala, pri čemu su omjeri promjera miješala i promjera kristalizatora, D/d T , iznosili 0,43, 0,53 te 0,63. Istovjetna ispitivanja su provedena u kristalizatoru s djelovanjem ultrazvuka amplitude snage od 20 % kao i u kristalizatoru bez ultrazvučnog djelovanja. Tijekom provedbe eksperimenata provodila se granulometrijska analiza rastućih kristala metodom laserske difrakcije te je sagledan utjecaj promjera SBT miješala na vremensku promjenu funkcije gustoće raspodjele kristala u sustavu sa i bez djelovanja ultrazvuka kao i na promjenu srednjeg volumnog promjera kristala te koeficijenta varijacije. Kako bi se dobio uvid o utjecaju hidrodinamičkih uvjeta u kristalizatoru na karakteristike rastućih kristala te detektirala pojava aglomeracije kristala i sekundarne nukleacije sagledavane su fotografije kristala analiziranih optičkim mikroskopom kao i njihova specifična površina. Granulometrijskom analizom konačnog produkta utvrđeno je da se s povećanjem miješala srednja veličina kristala u oba sustava povećava. U sustavima bez ultrazvuka također se povećava udio finijih i grubljih kristala u produktu uslijed povećane sekundarne nukleacije i aglomeracije. U sustavma s ultrazvukom aglomeracija je izbjegnuta, a kristali su bili gotovo dvostruko manji, ali pravilniji. Također je određena i snaga privedena uslijed miješanja i ultrazvučnog djelovanja. Utvrđeno je da se ona u oba sustava neznatno povećavala s veličinom miješala, a u sustavu s ultrazvukom je bila gotovo petnaest puta veća.The aim of this study was to examine the influence of impeller size in the crystallizer with and without the ultrasound irradiation on crystal growth of borax during batch crystallization at the critical impeller speed (N = N JS ). Crystallization is carried out in a laboratory scale crystallizer by cooling the mother liquor saturated at 30 °C to a temperature of 15 °C, at the rate of 6 °C h -1 . A radial straight four blade turbine (abbrev. SBT) was used in the work, and the influence of impeller size on the formed crystals properties was examined at impeller to crystallizer diameter ratios, D/d T , of 0.43, 0.53 and 0.63, respectively. The same examinations were conducted in a crystallizer with an ultrasound irradiation at amplitude of 20 %, as in a silent crystallizer as well. During the experiments, a granulometric analysis of the growing crystals was performed by the laser diffraction method, and influence of the SBT impeller diameter on the changes of volume density crystal size distribution over process time was analysed in the system with and without ultrasound. The changes of the volume mean crystal diameter and its coefficient of variation over process time were also determined. In order to gain insight into the influence of hydrodynamic conditions in the crystallizer on the growing crystals habit and to detect the appearance of crystal agglomeration and secondary nucleation, photographs of crystals analysed with an optical microscope as well as their specific surface area were analysed respectively. The granulometric analysis of the final product revealed that the average crystal size in both systems increased with an increase in impeller size. In the silent systems, the proportion of finer and coarser crystals in the product also increased due to increased secondary nucleation and agglomeration. In the irradiated systems agglomeration was avoided, while the crystals were more than twice as smaller, but of a more regular shape. The power consumption due to stirring and ultrasound irradiation was also determined. In in both systems it slightly increased with impeller size, but in the system with ultrasound it was almost fifteen times higher