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Electrochemical behaviour and analytical application of modified electrodes : bachelor thesis
No full textTrend pronalaska brzih tehnika probira i kvantifikacije virusa je u fokusu današnjih istraživanja, jer zahtjevi tržišta diktiraju ubrzanu dijagnostiku. Pronalazak metode kvantifikacije virusa bez opsežne pripreme uzoraka trenutno u svijetu predstavlja globalni problem, ali s druge strane otvara i mogućnost velike zarade farmaceutskim i drugim kompanijama. U ovom radu opisane su komercijalne i elektrokemijske metode u dijagnostici virusa, njihove prednosti i mane, te važnost primjene. U fokusu rada su modificirane elektrode za detekciju virusa koji najčešće pogađaju čovječanstvo, kako i kada se primjenjuju i zašto ih je važno razvijati, te njihove prednosti nad komercijalnim metodama određivanja virusa. Posebno su istraženi biosenzori za detekciju SARS-COVID-19, virusa koji je snažno pogodio čovječanstvo i njihova primjena u kvalitativnoj i kvantitativnoj analizi primjenom elektrokemijskih metoda.The trend of finding rapid virus screenings and quantifications techniques is the focus of today's researches because the market demands rapid diagnostics. Finding a method of virus quantification without extensive sample preparation is currently a global problem, but it also opens up the possibility of large profits for pharmaceutical and other companies. This paper describes commercial and electrochemical methods in virus diagnosis, their advantages and disadvantages, and the importance of their application. The focus of the paper are modified electrodes for the detection of viruses that most commonly affect humanity, how and when are they applied, why it's important to develop them, and their advantages over commercial methods of virus detection. In particular, biosensors for the detection of SARS-COVID-19, a virus that has strongly affected humanity, and their application in qualitative and quantitative analysis using electrochemical methods have been described
Radionica: Otvoreni pristup (OA)
No full textRadionica o otvorenoj znanosti organizira se s ciljem poticanja otvorenog pristupa znanstvenim informacijama i osvješćivanja važnosti istoga. Na radionici će se objasniti temeljna načela otvorene znanosti s naglaskom na otvoreni pristup, unutar kojega će se obraditi teme verzija radova za objavljivanje, autorskih prava, institucijskih repozitorija i mogućnosti pohrane radova u otvorenom pristupu uz demonstraciju istoga
RASFF system : bachelor thesis
No full textRASFF je sustav brzog uzbunjivanja za hranu i hranu za životinje, te kao takav je zaslužan za sigurnost hrane. Brza razmjena informacija sustavom omogućuje upućenost svih država članica, ali i trećih zemalja u zdravstveni rizik, te brzo poduzimanje mjera kada se utvrdi zdravstveni rizik. Cilj završnog rada bio je istražiti i napraviti analizu RASFF obavijesti, opoziva i povlačenja na području Hrvatske u vremenskom periodu od 01.01.2016. do 31.12.2020. Postoje četiri vrste obavijesti; hitna obavijest, obavijest za informaciju, obavijest o odbijanju s granice, te novosti. Da bi potrošač bio upućen u sve obavijesti koje se tiču hrane koju svakodnevno unosi u organizam, te opoziva i povlačenja istih proizvoda, uveden je RASFF portal, odnosno RASFF prozor. Ovaj sustav omogućava veću informiranost ljudi u vezi hrane. Provedba RASFF sustava u Hrvatskoj zakonski je regulirana Zakonom o hrani (“Narodne novine“, broj 81/13, 14/14), dok je njegova organizacija, komunikacija i način upravljanja istim određena Pravilnikom o sustavu brzog uzbunjivanja za hranu i hranu za životinje (“Narodne novine“, broj 155/2013). Ministarstvo poljoprivrede je kao Nacionalna kontakt točka zaduženo obavijestiti potrošače u slučaju pojave zdravstvenog rizika koji je uzrokovan hranom, te je zaduženo takav proizvod povući ili opozvati s tržišta. RASFF obavijesti, opozivi i povlačenja u vremenskom periodu od pet godina su prikazani grafovima. Najčešća kategorija opozvanih i povučenih proizvoda je kategorija meso peradi i proizvodi od mesa peradi, a najčešća kategorija opasnosti su patogeni mikrooorganizmi. Isto vrijedi i za obavijesti na području Hrvatske. Najviše RASFF obavijesti, opoziva i povlačenja je bilo u 2020. godini, a najmanje u 2016. godini.RASFF is a rapid alert system for food and feed, and as such is credited with food safety. The rapid exchange of information through the system enables all Member States, but also third countries, to be informed about health risks, and measures to be taken quickly when a health risk is identified. The aim of the final work was to investigate and analyze the RASFF notifications, recalls and withdrawals in Croatia in the period from 01.01.2016. to 31.12. 2020. There are four types of notifications; emergency notice, information notice, border rejection notice, and news. In order for the consumer to be informed about all the notifications regarding the food he ingests on a daily basis, and the recall and withdrawal of the same products, the RASFF portal, that is the RASFF window, has been introduced. This system enables greater information of people about food. The implementation of the RASFF system in Croatia is legally regulated by the Food Act (Official Gazette, No. 81/13, 14/14), while its organization, communication and management are determined by the Ordinance on rapid alert system for food and feed (Official Gazette 155/2013). The Ministry of Agriculture, as the National Contact Point, is in charge of informing consumers in the event of a health risk caused by food, and in charge of withdrawing or recalling such a product from the market. RASFF notifications, revocations and withdrawals over a period of five years are shown in graphs. The most common category of recalled and withdrawn products is the category of poultry meat and poultry meat products, and the most common category of danger are pathogenic microorganisms. The same applies to notifications in Croatia. The highest number of RASFF notifications, recalls and withdrawals was in 2020, and the lowest in 2016
Antioxidant activity of olive leaves : master thesis
No full textListovi masline (Olea europea L.) posjeduju veliki potencijal kao prirodni antioksidansi. Danas je sve veći broj istraživanja koji potvrđuju blagotvorne učinke lišća masline na ljudsko zdravlje, kao i mogućnost njihove primjene u prehrambenoj industriji. Cilj ovog rada bio je ispitati antioksidacijski kapacitet lišća masline sortiLastovka, Levantinkai divlje masline korištenjem različitih spektrofotometrijskih metoda temeljenih na različitim mehanizmima djelovanja: FRAP (engl. Ferric Reducing Antioxidant Power), ORAC (engl. Oxygen Radical Absorbing Capacity) i DPPH (engl. 2,2-diphenyl-1-picrylhydrazyl assay) metoda. Obzirom na sadržaj ukupnih fenola i antioksidacijski potencijal određen FRAP metodom, najbolju redukcijsku sposobnost pokazao je ekstrakt lista divlje masline. Najveći antioksidacijski kapacitet i sposobnost neutralizacije hidroperoksil radikala pokazao je ekstrakt kultivirane sorte Levantinka. Rezultati svih testiranih uzoraka ukazuju na veliki biološki potencijal ekstrakta lista masline te mogućnosti njegove primjene u prehrambenoj industriji.Olive leaves (Olea europea L.) have great potential as natural antioxidants. Today, a growing number of studies confirm the beneficial effect of olive leaves on human health, but also the possibility of their use in the food industry. The aim of this study was to examine antioxidant activity of olive leaves of Lastovka, Levantinkaand wild oliveusing different spectrophotometric methods based on different mechanisms of action: FRAP (Ferric Reducing Antioxidant Power), ORAC (Oxygen Radical Absorbing Capacity) and DPPH (2,2-diphenyl-1-picrylhydrazyl assay) method. Based on the content of total phenolics and antioxidant potential determined by FRAP method, the best reducing ability was obtained for wild olive leaf extract. The highest antioxidant capacity and ability to neutralize hydroperoxyl radicals was shown by the extract of the cultivated olive variety Levantinka.The obtained results for all tested samples indicate a great biological potential of olive leaf extractsand the possibility of their application in the food industry
Preparation and electrochemical characterization of cobalt, nickel and copper complex with 2 and 6 hydroxynicotinic acid : master thesis
No full textMetalno–organski koordinacijski spojevi privlače sve veći interes zbog svojih intrigantnih strukturnih karakteristika kao i željenih performansi, uključujući senzorsku tehnologiju, luminescenciju, ionsku izmjenu, katalitička svojstva itd. Pažljivo odabrani organski ligandi s određenim značajkama, kao što su multidentatni i kruti ligandi s multiprotonskim akceptorskim ili donorskim mjestima, mogu se koristiti kao premošćujući ligandi, korisni u konstrukciji i krojenju koordinacijskih spojeva željenih svojstva. Metalni koordinacijski spojevi odgovarajućih organskih liganda mogu omogućiti mjenjanje i kontrolu redoks svojstava. U ovom radu predstavljena je hidrotermalna sinteza (130 o C, 72 sata) kompleksnih spojeva dvovalentnih kationa prijelaznih metala (Co, Ni i Cu) i odabranih derivata nikotinske kiseline (2– hidroksinikotinska i 6–hidroksinikotinska kiselina). Dobiveni kompleksni spojevi karakterizirani su IR spektroskopijom, termogravimetrijom (TG), diferencijalnom termičkom analizom (DTA) i elektrokemijski. Elektokemijska karakterizacija provedena je u 0,1 M KNO 3 korištenjem elektode od staklastog ugljika (GC) modificirane suspenzijom jednozidnih ugljikovih nanocjevčica (SWCNT) i dobivenih kompleksnih spojeva. Na temelju TGA/DTA krivulja i IR spektra, kao i poznatih kristalnih struktura za; [Co(H 2 O) 6 ](6–OHnic) 2 , Co(2–OHnic) 2 (H 2 O) 2 ] i [Ni(H 2 O) 6 ](6–OHnic) 2 pretpostavljeno je da je koordinacija 6–hidroksinikotinske kiseline (6–OHnic) kod kompleksa Cu(II) O,O–asimetrično kelatirajuća (preko kisikovih atoma karboksilne skupine) dok je koordinacija 2–hidroksinikotinske kiseline (2–OHnic) O,O– kelatirajuća (preko atoma kisika karboksilne skupine i atoma kisika amidne skupine).Metal–organic coordination compounds attract increasing interest due to their intriguing structural characteristics as well as desired performances, including sensor technology, luminescence, ion exchange, catalytic properties, etc. Carefully selected organic ligands with certain features, such as multidentate and rigid ligands with multi–proton acceptor or donor sites, might be utilized as versatile linkers, being useful in constructing and tailoring coordination compound with desirable properties. Metal coordination compound of suitable organic ligands potentially allow the variation and control of redox properties. Herein, we present the hydrothermal synthesis (130 o C, three days) of coordination compounds of divalent transition metal cations (Co, Ni and Cu) and selected nicotinic acid derivatives (2–hydroxynicotinic and 6– hydroxynicotinic acid). The obtained complexes are characterized by IR spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA) and electrochemically. Electrochemical characterization was performed in 0.1 M KNO 3 using a glassy carbon (GC) electrode modified with a suspension of single–walled carbon nanotubes (SWCNT) and the obtained complex compounds. Based on TGA/DTA curves and IR spectra, as well as known crystal structures for; [Co (H 2 O) 6 ](6– OHnic) 2 , Co(2–OHnic) 2 [H 2 O) 2 ] and [Ni(H 2 O) 6 ](6–OHnic) 2 it is proposed that the coordination of 6–hydroxynicotinic acid (6–OHnic) in the Cu (II) complex is O,O– asymmetrically chelating (via oxygen atoms of the carboxyl group) while the coordination of 2–hydroxynicotinic acid (2–OHnic) is O,O–chelating (via the oxygen atom of the carboxyl group and the oxygen atom of the amide group)
Carbon based sensor for the determination of the antidepressant maprotiline : master thesis
No full textPripravljena je ionsko selektivna elektroda na bazi ugljika uz dodatak ionsko asocijacijskog kompleksa (IAC). Pripravljena elektroda je primijenjena za odreĊivanje antidepresiva maprotilina (MAP) u koncentracijskom podruĉju od 3,16 x 10 -5 – 3,16 x 10 -3 M pri pH = 4. Pripravljeno je i testirano 25 membrana s razliĉitim udjelima IAC-a, grafita i veziva, ili uz dodatak soli, ionofor i grafen. Membrana s udjelom 47,08% grafita, 46,95% veziva i 5,97% IAC-a pokazuje linearnu promjenu potencijala u rasponu koncentracija od 3,16 x 10 -6 do 3,16 x 10 -3 s promjenom potencijala po koncentracijskoj dekadi od 51,60 mV. Membrana sastava 45,85% grafita, 45,26% veziva i 8,89% IAC-a pokazuje linearnu promjenu potencijala u rasponu koncentracija od od 3,16x10 -6 do 3,16x10 -3 s promjenom potencijala po koncentracijskoj dekadi od 51,84mV.A carbon-based ion-selective electrode was prepared with the addition of an ion-association complex (IAC) in certain ratios and was used to determine the antidepressant maprotiline (MAP) in the concentration range of 3,16 x 10 -6 to 3,16 x 10 -3 M at pH = 4. Twenty five membranes with different proportions of IAC, graphite and binder were prepared and tested, and salt, ionophore and graphene were added to some of these membranes. Membrane 5 with(47.08% graphite, 46.95% binder and 5.97% IAC) a Nernstian slope of 51.60 mV / decade and membrane 6 (45.85% graphite, 45.26% binder and 8.89% IAC) with a slope of 51.84 mV / decade proved to be the best membranes
Data visualisation of municipal solid waste management : bachelor thesis
No full textU radu su analizirani podatci o količini oporabljenog/zbrinutog krutog komunalnog otpada i to postupcima energetske oporabe i recikliranja, kao i podaci o količini komunalnog otpada koja je neobrađena odložena na odlagališta u Republici Hrvatskoj i u Dubrovačko-neretvanskoj županiji u razdoblju od 2014. do 2017. godine. Rezultati analize prikazani su ternarnim dijagramom. Vizualizacijom podataka o postupcima oporabe/zbrinjavanja otpada moguće je lako i brzo razumijevanje informacija kako bi se olakšalo donošenje informiranih odluka, planiranje poslovanja i usmjeravanje gospodarenja otpadom na strateškoj razini prema kružnom gospodarstvu.This paper analyses the amount of municipal solid waste recovered/disposed, including energy recovery and recycling processes, as well as the amount of municipal waste disposed at landfills in the Republic of Croatia and in the Dubrovačko-neretvanska County from 2014 to 2017. The results of the analysis are presented by a ternary diagram. By visualizing data of waste recovery/disposal operations, it is possible to understand information easily and faster. Also, the data visualisation facilitates the use of information in waste management decision making and promotes the circular economy
The comparison of making of calibration curves on Perkin Elmer Lambda spectrophotometers : bachelor thesis
No full textU ovom završnom radu uspoređena je izrada krivulja umjeravanja za dva različita spektorofotometra proizvođača Perkin Elmer: Lambda 25 i Lambda EZ 201. Pripremljene su vodene otopine bakrovog(II) klorida dihidrata te kobaltovog(II) klorida heksahidrata kojima su izmjerene odgovarajuće apsorbancije te izrađene krivulje umjeravanja. Iako se radi o dva različita modela, linearno dinamičko područje je za obje krivulje umjeravanja identično. S obzirom da je spektrofotometar Perkin Elmer Lambda 25 novije generacije, rad na njemu je precizniji. Osim toga, njime se upravlja uz pomoć programske podrške te nudi mogućnost pohrane krivulje umjeravanja.In this bachelor thesis, a comparison of making of calibration curves for two different spectrophotometers manufactured by Perkin Elmer: Lambda 25 and Lambda EZ 201 was examined. Aqueous solutions of copper(II) chloride dihydrate and cobalt(II) chloride hexahydrate were prepared and the corresponding absorbances were measured and calibration curves were constructed. Although these are two different models, linear dynamic range of both calibration curves obtained are identical. Since the Perkin Elmer Lambda 25 spectrophotometer is of a newer generation, the work on it is more accurate. In addition, it is managed by software and offers the ability to store the calibration curve
Measurment of scavenging ability of superoxide anion radicals with hydrolates of selected plants using xanthine/xanthine oxidase method : diploma thesis
No full textSlobodni radikal je bilo koja vrsta koja može samostalno postojati, a sadrži jedan ili više nesparenih elektrona. Reaktivne kisikove vrste nastaju iz molekulskog kisika kao rezultat normalnog staničnog metabolizma. Superoksidni anion radikal, hidroksil radikal i vodikov peroksid su vrste od fiziološkog značaja. Superoksidni anion se formira adicijom jednog elektrona molekulskom kisiku, a proces može biti popraćen ksantin-oksidazom. Antioksidans je tvar koja odlaže, sprječava ili uklanja oksidativna oštećenja ciljne molekule. Ljudski organizam endogeno posjeduje različite antioksidanse kako bi stvorili protutežu efektu oksidansa. U ovom radu testirani su hidrolati odabranih biljaka metodama ksantin/ksantin- oksidaza, DPPH, FRAP i Folin-Ciocalteu Najbolji antioksidacijski potencijal testiran DPPH i FRAP metodom pokazuju hidrolati biljaka Juniperus communis ssp. nana, Moltkia petraea i Mantisalca salmantica. Rezultati su u skladu sa sadržajem ukupnih fenola testiranih hidrolata. Ksantin/ksantin- oksidaza metodom u testiranoj koncentraciji od 1 g/L gotovo svi hidrolati pokazuju dobru sposobnost hvatanja superoksid anion radikala. Uzorci pokazuju dobru i o koncentraciji neovisnu sposobnost inhibicije superoksid anion radikala. Rezultati dobiveni testiranjem sposobnosti hvatanja superoksid anion radikala ksantin/ksantin-oksidaza metodom nisu u korelaciji s rezultatima dobivenim metodama DPPH, FRAP i Folin-Ciocalteu. Za dobivanje mjerodavnih rezultata metodom ksantin/ksantin-oksidaza potrebno je testirati sposobnost hidrolata da inhibiraju enzim ksantin-oksidazu te testirati uzorke i neenzimatskom metodom hvatanja superoksid anion radikalaA free radical is any species that can exist independently and contains one or more unpaired electrons. Reactive oxygen species are produced from molecular oxygen as a result of normal cellular metabolism. Superoxide anion radical, hydroxyl radical and hydrogen peroxide are species of physiological importance. The superoxide anion is formed by the addition of one electron to molecular oxygen, and the process can be catalised by xanthine oxidase. An antioxidant is a substance that delays, prevents or eliminates oxidative damage to the target molecule. The human body endogenously possesses various antioxidants to counterbalance proxidant processes. In this paper the hydrolates of selected plants were tested using xanthine/xanthine oxidase, DPPH, FRAP and Folin-Ciocalteu methods. The best antioxidant potential tested by the DPPH and FRAP method is shown by the hydrolates of plants of Juniperus communis ssp. Nana, Moltkia petraea and Mantisalca salmantica. The results are consistent with the total phenol content of the tested hydrolates. Xanthine/xanthine oxidase method at a tested concentration of 1 g/L, almost all the hydrolates show good ability to capture the superoxide anion radical. The samples show good and concentration independent ability to inhibit superoxide anion radicals. The results obtained by testing the superoxide anion trapping capability of the xanthine/xanthine oxidase method did not correlate with the results obtained by the DPPh, FRAP and Folin-Ciocalteu methods. In order to obtain relevant results by the xanthine/xanthine oxidase, it is necessary to test the ability of the hydrolates to inhibit the enzyme xanthine oxidase and to test the samples with a non-enzymatic method of trapping the superoxide anion radical
Volatile compounds of beer : diploma thesis
No full textU ovom radu analiziran je kemijski sastav hlapljivih spojeva komercijalnih piva pivskih stilova: pale lager, dunkel, pale ale i hefeweizen. Hlapljivi spojevi izolirani su metodom mikroekstrakcije vršnih para na krutoj fazi (HS-SPME) korištenjem dva različita vlakna te su analizirani vezanim sustavom plinska kromatografija–spektrometrija masa (GC-MS), a dobiveni rezultati su uspoređeni. Identificirani spojevi mogu se svrstati u sljedeće kemijske skupine: alkoholi, esteri, terpenski spojevi i karbonilni spojevi.In this paper, the chemical composition of volatile compounds of commercial beers of beer styles: pale lager, dunkel, pale ale and hefeweizen, was analyzed. Volatile compounds were isolated by solid phase microextraction (HS-SPME) with two different fibers and were analyzed by the gas chromatography – mass spectrometry (GC-MS) system in order to compare the results obtained. The identified compounds can be classified into the following chemical groups: alcohols, esters, terpene compounds and carbonyl compounds