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Electrocatalytic activity of nickel for hydrogen evolution reaction : bachelor thesis
No full textElektrokatalitička svojstva nikla za reakciju razvijanja vodika u 1 mol dm -3 NaOH simulirana su korištenjem zadanih vrijednosti. Simulacija struja – potencijal odgovora elektrode od nikla za reakciju razvijanja vodika u otopini NaOH koncentracije 1 mol dm -3 na temperaturi 25 ˚C za područje prenapona od -120 mV do -280 mV izvršena je korištenjem računalnog programa SigmaPlot. Korištenjem zadanog nagiba katodnog Tafelovog pravca (110 mV dec -1 ) te gustoće struje izmjene (1,7 x 10 -6 A cm -2 ) modeliran je odziv nikla pri linearnoj polarizaciji te prikazan u obliku odgovarajućih grafova. Simulacija impedancijskog odziva elektrode od nikla za reakciju razvijanja vodika u otopini NaOH koncentracije 1 mol dm -3 na temperaturi 25 ˚C za područje prenapona od -100 mV do -250 mV izvršeno je korištenjem računalnog programa ZView. Elektrokemijski impedancijski spektri modelirani su primjenom Randlesovog električnog ekvivalentnog kruga i prikazani su u Nyquistovom i Bodeovom prikazu. Iz rezultata elektrokemijske impedancijske spektroskopije određeni su hrapavost elektrode, gustoća struje izmjene i nagib katodnog Tafelovog pravca.The electrocatalytic properties of nickel for hydrogen evolution reaction in 1 mol dm -3 NaOH was simulated by using default values. Simulation of current – potential electrode response for hydrogen evolution reaction in 1 mol dm -3 NaOH solution at 25 ˚C for overvoltage range from -120 mV to -280 mV was performed using the computer program SigmaPlot. Using a given Tafel slope of 110 mV dec -1 and exchange current density od 1,7 x 10 -6 A cm -2 , the nickel response at linear polarization was modeled and presented in the form of corresponding graphs. Simulation of the impedance response of a nickel electrode for the hydrogen evolution reaction in a NaOH solution with a concentration of 1 mol dm -3 at a temperature of 25 ˚C for the overvoltage range from -100 mV to -250 mV was performed using the computer program ZView. Electrochemical impedance spectra were modeled using the Randles electrical equivalent circuit and presented in form of Nyquist and Bode plot. From the results of electrochemical impedance spectroscopy, the electrode surface roughness, exchange current density and Tafel slope were determined
Development of sensors for determination of maprotiline antidepressors with different binders and precipitation reagents : master thesis
No full textElektrode na bazi ugljikove paste (CPE) pronašle su svoju primjenu u elektrokemijskim i elektroanalitiĉkim metodama analize. Rijeĉ je o elektrodama ĉije su smjese ugljikovih pasti pripremljene od ugljikovog materijala (grafita), veziva te soli i ionsko- asocijacijskog kompleksa (IAC) u razliĉitim omjerima. Pripremljeno je 25 pasta s ciljem pronalaska senzora za odreĊivanje maprotilina u realnim uzorcima u koncentracijskom podruĉju od 3,16∙10 -6 do 3,16∙10 -3 mol L -1 pri pH vrijednosti 4. Najbolje odzivne karakteristike pokazala je pasta napravljena od grafita, dioktil ftalata, soli i ionsko-asocijacijskog kompleksa MAP TPB. Promjena potencijala po koncentracijskoj dekadi je u rasponu od 56,4 do 83,9 mV , MeĊutim, najbolja promjena potencijala po koncentracijskoj dekadi zabiljeţena je kada elektroda nije bila polirana i iznosila je 58,9 odnosno 59,6 mV. Linearno podruĉje je u rasponu koncentracija od 3,16∙10 -6 do 3,16∙10 -3 mol L -1 .Carbon paste electrodes (CPE) have found their application in electrochemical and electroanalytical methods of analysis. These are electrodes whose mixtures of carbon pastes are prepared from carbon material (graphite), binder , salt and ion-association complex (IAC) in different proportions. 25 pastes were prepared in order to develope a sensor for determination maprotiline in real samples in the concentration range from 3,16∙10 -6 to 3,16∙10 -3 mol L -1 at pH 4. The paste made of graphite, dioctyl phthalate, salt and the ion-association complex MAP TPB showed the best response characteristics. The change in potential per concentration decade ranges from 56,4 to 83,9 mV. However, the best change in potential per concentration decade was recorded when the electrode was not polished and was 58,9 and 59,6 mV, respectively. The linear range is in the concentration range from 3.16 ∙ 10 -6 to 3.16 ∙ 10 -3 mol L -1
Characterization of volatile compounds in gin : diploma thesis
No full textGin je jako, u pravilu bezbojno alkoholno piće dobiveno aromatiziranjem etilnog alkohola poljoprivrednog podrijetla bobicama borovice i drugim biljkama. Minimalni udio alkohola u ginu je 37,5% vol. Cilj ovog rada bio je utvrditi i usporediti profil hlapljivih spojeva četiri različita uzorka gina. Hlapljivi spojevi izolirani su mikroekstrakcijom vršnih para na čvrstoj fazi (HS-SPME), koristeći dva vlakna različite polarnosti, a identificirani vezanom tehnikom plinska kromatografija-spektrometrija masa (GC- MS). Identificirano je ukupno 37 hlapljivih spojeva iz skupina terpena, terpenoida, estera i fenilpropana. 14 spojeva je pronađeno u svim uzorcima, od kojih je 13 već prije identificirano u eteričnom ulju borovice (Juniperus communis). Etil-acetat koji je identificiran u svim uzorcima predstavlja sastavni dio destiliranih pića koji nastaje za vrijeme alkoholne fermentacije esterifikacijom etanola i octene kiseline. Razlike u aromatskim profilima uzoraka posljedica su različite recepture i proizvodnih procesaGin is a generally colourless spirit produced by flavouring ethyl alcohol of agricultural origin with juniper berries and other plant material. The minimum alcohol content in gin is 37.5% ABV (alcohol by volume). The aim of this study was to determine and compare the volatile compound profile of four different gin samples. The volatile compounds were isolated by headspace-solid phase microextraction (HS-SPME), using two fibers of different polarity, and identified by gas chromatography-mass spectrometry (GC- MS) technique. A total of 37 volatile compounds from the group of terpenes, terpenoids, esters and phenylpropanes were identified. 14 compounds were found in all samples, of which 13 had previously been identified in the essential oil of juniper berries (Juniperus communis). Ethyl acetate identified in all samples is commonly found in distilled spirits as a product formed during alcoholic fermentation by esterification of ethanol and acetic acid. Differences in the aromatic profiles of the samples are due to different recipes and production processes
Determination of penicillamine in pharmaceutical formulations using kinetic method with spectrofhotometric detector : master thesis
No full textKorištenjem kinetičke spektrofotometrije razvijena je i vrednovana nova metoda određivanja penicilamina (PEN) u farmaceutskim pripravcima. Metoda se temelji na redoks reakciji između bis batokuproin bakrov(II) kompleksa i penicilamina pri čemu nastaje stabilan kompleks narančaste boje, bis batokuproin bakrov(I) kompleks. Nastali kompleks postiže apsorpcijski maksimum pri valnoj duljini od 483 nm. Optimizirani su parametri koji utječu na kemijsku reakciju. Kod izrade krivulja umjeravanja korištene su metoda početne brzine i metoda odabranog vremena. Krivulja umjeravanja metodom početne brzine linearna je u području koncentracija od 6,0 × 10 −7 do 4,0 × 10 −5 mol L −1 , s granicom dokazivanja od 1,8 × 10 −7 mol L –1 . Nagib krivulje umjeravanja dobiven metodom početne brzine (1,0448) potvrđuje reakciju pseudoprvog reda. Krivulja umjeravanja metodom odabranog vremena (prva minuta) linearna je u području koncentracija od 2,0 × 10 −7 do 4,0 × 10 −5 mol L −1 , s granicom dokazivanja od 6,0 × 10 −8 mol L –1 . Predložena metoda uspješno je primijenjena kod određivanja penicilamina u komercijalnim farmaceutskim pripravcima što je uspoređeno s rezultatima dobivenim preporučenom metodom po farmakopeji.Kinetic spectrophotometry was employed for development and validation of new method for determination of penicillamine (PEN) in pharmaceutical formulation. The method is based on a redox reaction in which the reduction of copper(II) – neocuproine by penicillamine occurs, with formation of stable coloured, yellow-orange complex of copper(I) – neocuproine. The resulting complex exhibits an absorption maximum at λ = 483 nm. The parameters of chemical reaction have been optimized. The initial rate and fixed time methods were utilized for constructing the calibration graphs. The graph for initial rate method was linear in concentration range from 6,0 × 10 −7 do 4,0 × 10 −5 mol L −1 with the limit of detection 1,8 × 10 −7 mol L –1 . The slope of the initial method calibration curve (1.0448) confirmed the first order reaction. The graph for fixed time method (1 min) was linear in concentration range from 2,0 × 10 −7 do 4,0 × 10 −5 mol L −1 with the limit of detection 6,0 × 10 −8 mol L –1 . No interferences were observed from the excipients that are commonly present in the pharmaceutical formulations. The proposed method was successfully applied for the determination of PEN in its commercial pharmaceutical formulation, which is compared to the results obtained by the recommended method in Pharmacopoeia
Program osnaživanja bibliometrijskih usluga u visokoškolskim knjižnicama Sveučilišta u Splitu: radionica 5. analiza znanstvene produktivnosti ustanove
No full textZnanstvena aktivnost nastavnika i suradnika KTF-a odvija se u području prirodnih, tehničkih i biotehničkih zanosti, odnosno u poljima kemija, kemijsko inženjerstvo i prehrambena tehnologija. Nastavnici i suradnici KTF-a aktivni su i u području prirodnih znanosti, polje fizika i polje matematika te u području biomedicine i zdravstva, polje farmacija. Postupak akreditacije: svibanj 2021. godine. Izrada afilijacije: WOS, SCOPUS, CROSB
Hg (II) sorption on Fe (III) - modified zeolite clinoptilolite - determination of the sorption mechanism : bachelor thesis
No full textProvedena je kemijska modifikacija prirodnog zeolita s otopinom Fe(III) iona te su ispitana sorpcijska svojstva polaznog uzorka prirodnog zeolita klinoptilolita te dobivenog Fe(III)-modificiranog zeolita prema ionima Hg(II) pri unaprijed definiranim optimalnim uvjetima, pH o = 2 i omjeru kruto/tekuće 10 g/L. Sorpcijski kapacitet Fe(III)-modificiranog zeolita prema Hg(II) ionima iznosi 0,54 mmol/g što je dvostruko više u usporedbi s prirodnim zeolitom (0,28 mmol/g). Sorpcijski mehanizam Hg(II) na Fe(III)-modificiranom zeolitu uključuje prvenstveno ionsku izmjenu popraćenu površinskim kompleksiranjem i koprecipitacijom, što je potvrđeno određivanjem koncentracije izmjenjivih zeolitnih kationa kao i SEM-EDS analizom živom zasićenog Fe(III)-modificiranog zeolita.Chemical modification of natural zeolite with a solution of Fe(III) ions was carried out, and the sorption properties of the starting sample natural zeolite clinoptilolite as well as obtained Fe(III)-modified zeolite towards Hg(II) ions were tested at predefined optimal conditions, pH o = 2 and solid/liquid ratio 10 g/L. The sorption capacity of the Fe(III)-modified zeolite towards Hg(II) ions is 0.54 mmol/g, which is twice as much compared to the natural zeolite (0.28 mmol/g). The sorption mechanism of Hg(II) on the Fe(III)-modified zeolite includes primarily ion exchange accompanied by surface complexation and co-precipitation, which was confirmed by determining the aconcentration of exchangeable zeolite cations as well as by SEM-EDS analysis of mercury-saturated Fe(III)-modified zeolite
Seasonal difference in hydrodistillates chemical composition of alga cladostephus spongiosus : master thesis
No full textAlge su fotosintetski autotrofni organizmi koji nastanjuju praktički sva staništa. Dijele sa na mikroalge i makroalge. Prema pigmentu kojeg sadržavaju dijele se u 3 grupe: smeđe (Phaeophyta), zelene (Chlorophyta) i crvene (Rhodophyta) alge. Smeđe alge žive isključivo u morima, najčešće su pričvršćene na kamenu podlogu, stijene ili druge organizme. Karakterističnu smeđu boju daje im smeđi pigment fukoksantin koji maskira klorofil i ostale karotenoide. Smeđa makroalga Cladostephus spongiosus (Hudson) C. Agardh 1817 široko je rasprostranjena u Sredozemnom moru, a može se naći i uz atlantske obale Maroka do Irske. Provedena je analiza na svježem i suhom uzorku alge C. spongiosus uzorkovane u svibnju (pri temperaturi mora 20,01 °C) i kolovozu (pri temperaturi mora 28,01 °C). Vezanim sustavom plinske kromatografije sa spektrometrijom masa analizirani su isparljivi spojevi hidrodestilata dobiveni primjenom hidrodestilacije modificiranom aparaturom po Clevengeru. Usporedbom dobivenih rezultata primijećene su razlike u udjelu terpena, derivata klorofila, masnih kiselina i derivata te alifatskih zasićenih i nezasićenih spojeva obzirom na mjesec uzorkovanja. U uzorku C. spongiosus uzorkovanom u svibnju najzastupljeniji su terpeni (48,70%, svježe; 38,05%, suho) dok u uzorku iz kolovoza njihov sadržaj značajno opada (12,57%, svježe; 17,20%, suho). Razlika je uočena i kod zastupljenosti derivata klorofila čiji je udio u uzorku iz kolovoza (16,07%, svježe; 19,37%, suho) gotovo trostruko veći od udjela iste skupine spojeva u uzorku iz svibnja (5,29%, svježe; 7,36%, suho). Na temelju provedenog istraživanja može se zaključiti da temperatura mora utječe na kemijski sastav alge C. spongiosus.Algae are photosynthetic autotrophic organisms that inhabit virtually all habitats. They are divided into microalgae and macroalgae. According to the pigment they contain, they are divided into 3 groups: brown (Phaeophyta), green (Chlorophyta) and red (Rhodophyta) algae. Brown algae live exclusively in the seas, they are most often attached to rock surfaces, rocks or other organisms. The brown pigment fucoxanthin, which masks chlorophyll and other carotenoids, gives them their characteristic brown colour. The brown macroalga Cladostephus spongiosus (Hudson) C. Agardh 1817 is widely distributed in the Mediterranean Sea and it could be found in the Atlantic coasts from Morocco to Ireland. The analysis was performed on a fresh and dry sample of C. spongiosus alga sampled in May (at a sea temperature of 20.01 °C) and August (at a sea temperature of 28.01 °C). The coupled gas chromatography system with mass spectrometry was used for the volatile hydrodistillate compounds analysis. By comparing the obtained results, differences in the abundance of terpenes, chlorophyll derivatives, fatty acids and derivatives and aliphatic saturated and unsaturated compounds were observed with respect to the month of sampling. In the sample of C. spongiosus from May, terpenes are most represented (48.70%, fresh; 38.05%, dry), while in the sample from August their content remarkably decreases (12.57%, fresh; 17.20%, dry). The difference was also observed in the presence of chlorophyll derivatives whose abundance in the sample from August (16.07%, fresh; 19.37%, dry) was almost three times higher than the abundance of the same group of compounds in the sample from May (5.29%, fresh; 7.36%, dry). On the basis of the conducted research, it can be concluded that the sea temperature affects the chemical composition of the alga C. spongiosus
Influence of organically modified montmorilonite Cloisite 25A and lithium bis(oxalato)borate on the structure and thermal properties of poly(ethylene oxide) : master thesis
No full textPolimerni nanokompoziti dobiveni su miješanjem poli(etilen-oksida) molekulske mase, M ̅ v =1 000 000 (PEO10) s nanopunilom Cloisite 25A (25A) u masenim omjerima PEO10/25A 90/10, 80/20, 70/30, 60/40, 50/50 i 40/60 metodom interkalacije iz taljevine. Polimerni nanokompozitni elektroliti dobiveni su miješanjem PEO10 s 25A u navedenim omjerima uz dodatak soli litijevog bis(oksalato)borata (LiBOB) u količini da se zadovolji omjer 1:8 (Li : kisik iz PEO10) također metodom interkalacije iz taljevine. Primjenom diferencijalne pretražne kalorimetrije (DSC) ispitivan je utjecaj dodatka nanopunila 25A i utjecaj dodatka soli LiBOB na toplinske prijelaze i kristalnost PEO10 u PEO10/25A i PEO10/25A/LiBOB uzorcima. Utvrđeno je da dodatak nanopunila 25A značajnije ne utječe na staklište, ali snižava kristalnost PEO10. Dodatak soli LiBOB u potpunosti narušava kristalnu strukturu PEO10. Primjenom termogravimetrijske analize (TGA) ispitivana je toplinska postojanost i utjecaj dodatka 25A i utjecaj dodatka soli LiBOB na toplinsku razgradnju PEO10 u PEO10/25A i PEO10/25A/LiBOB uzorcima. Utvrđeno je da se dodatkom nanopunila 25A snižava toplinska postojanost PEO10, a dodatak soli LiBOB na nju neznatno utječe. Primjenom infracrvene spektroskopije s Fourierovom transformacijom (FT-IR) ispitivan je utjecaj 25A i utjecaj dodatka soli LiBOB na strukturu PEO10 u PEO10/25A i PEO10/25A/LiBOB uzorcima. Dodatak 25A i soli LiBOB utječu na konformaciju PEO10, uz izraženiji utjecaj soli LiBOB.Polymer nanocomposites were obtained by mixing poly(ethylene oxide) of molecular weight M ̅ v =1 000 000 (PEO10) with Cloisite 25A (25A) nanofiller in weight ratios PEO10/25A 90/10, 80/20, 70/30, 60/40, 50/50 and 40/60 by the melt intercalation method. Polymer nanocomposite electrolytes were obtained by mixing PEO10 with 25A in the indicated ratios with the addition of lithium bis (oxalate) borate (LiBOB) salt in an amount to meet the 1: 8 ratio (Li: oxygen from PEO10) also by melt intercalation method. Using differential scanning calorimetry (DSC), the effect of nanofiller 25A addition and the effect of LiBOB salt addition on thermal transitions and PEO10 crystallinity in PEO10/25A and PEO10/25A/LiBOB samples were investigated. It was found that the addition of 25A does not significantly affect glass transition but lowers degree of crystallinity of PEO10. Addition of LiBOB salt completely disrupts the crystal structure of PEO10. Thermogravimetric analysis (TGA) was used to investigate the thermal stability and the effect of additive 25A and the effect of the addition of LiBOB salt on the thermal decomposition of PEO10 in PEO10/25A and PEO10/25A/LiBOB samples. Nanofiller 25A was found to reduce the thermal stability of PEO10, and the addition of LiBOB salt slightly affected it. Using Fourier transform infrared spectroscopy (FT-IR), the effect of 25A and the effect of the addition of LiBOB salt on the structure of PEO10 in PEO10/25A and PEO10/25A/LiBOB samples were investigated. 25A nanofiller and LiBOB salts affect the PEO10 conformation, with a more pronounced influence of LiBOB salts
Testing membrane response based on NiS:Ag2S:PTFE=1:1:2 with the addition of hematite and aluminium nanoparticles : bachelor thesis
No full textIspitan je odziv ionsko-selektivnih membrana na niklove(II) ione pri pH = 1 i pH = 2, te utjecaj dodatka različitih postotaka nanočestica željezovih i aluminijevih oksida na odziv membrana. Membrane su sastavljene od niklovog(II) sulfida, srebrovog sulfida i teflona koji osigurava čvrstoću membrane, dok su nanočestice magnetita, hematita, akaganeita te aluminijeva oksida dodavane u postotcima od 1, 0,5 i 0,25 %. Ukupno je testirano 13 membrana uključujući referentnu membranu te su grafički prikazani rezultati koji su pokazali najbolji odziv. Svako mjerenje je ponovljeno minimalno tri puta. Ispitivanje odziva izvršeno je potenciometrijski zbog jednostavnosti i praktičnosti metode. Membrane su se ispitivale u elektrokemijskoj ćeliji koristeći otopinu niklovog(II) sulfata, pripremljenu u otopini perklorne kiseline pH=1 i u 0,1M otopini klorovodične kiseline pH=2, metodom slijednog razrjeđivanja. Za svako mjerenje zabilježena je vrijednost elektrodnog potencijala.The response of ion-selective membranes to nickel(II) ions at pH = 1 and pH = 2 was tested, as well as the influence of the addition of different percentages of nanoparticles of iron and aluminum oxides on the response of the membranes. The membranes are composed of nickel(II) sulfide, silver sulfide, and teflon, which ensures the strength of the membrane, while nanoparticles of magnetite, hematite, akaganeite, and aluminum oxide were added in percentages of 1, 0.5, and 0.25%. A total of 13 membranes were tested, including the reference membrane, and the results that showed the best response are shown graphically. Each measurement was repeated a minimum of three times. The response test was performed potentiometrically due to the simplicity and practicality of the method. The membranes were tested in an electrochemical cell using a nickel(II) sulfate solution, prepared in a perchloric acid solution pH=1 and in 0.1M hydrochloric acid solution pH=2, using a similar dilution method. For each measurement, the value of the electrode potential was recorded
Binding of lead ions to zeolite onto the presence of Humistar r solution of different concentration and ptf values : diploma thesis
No full textU ovom radu ispitano je vezanje iona olova na prirodnom zeolitu klinoptilolitu u prisutnosti otopine Humistar ® koja sadrži visoki udio huminskih kiselina i drugih organskih spojeva te tako simulira organske tvari prisutne u tlu. Eksperimenti su provedeni s otopinama različitih početnih koncentracijama iona olova te je ispitan utjecaj prisustva huminskih kiselina na točnost određivanja koncentracije olova metodom kompleksometrijske titracije. Eksperimenti vezanja olova na prirodnom zeolitu u otopinama različitih početnih koncentracija olova i različitih početnih koncentracija Humistar ® otopina provedeni su pri različitim pH vrijednostima. Pri višim koncentracijama iona olova utvrđena je veća količina vezanog olova po gramu zeolita, a najveće vrijednosti su dobivene uz dodatak 0,06% otopine Humistar®. Pri nižim početnim koncentracijama olova, dodatak otopine Humistar ® udvostručilo je količinu vezanog olova, a porastom koncentracije Humistara ® vrijednosti su se uvećale za tri puta u odnosu na kontrolnu suspenziju. Pri tome nije bilo utjecaja pH vrijednosti na kapacitet vezanja. Najviši stupanj uklanjanja olova je dobiven za niže koncentracije olova i uz veći dodatak Humistara ® . Temeljem dobivenih rezultata može se zaključiti da bi prisutnost organske tvari u tlu mogla povećati učinkovitost uklanjanja pri remedijaciji teških metala primjenom prirodnog zeolita.In this work, the binding of lead ions on the natural zeolite clinoptilolite has been examined in the presence of Humistar ® solution, with high amount of humic acids and other organic compounds simulating the organic matter found in the soil. Experiments have been conducted in solutions with different initial concentrations of lead ions, and the influence of the humic acids on the accuracy of lead determination by the complexometric titration has been examined. The lead ions removal on natural zeolite in solutions of different initial concentrations of lead and different concentrations of Humistar ® solutions have been performed at different pH values. At the higher concentrations of lead ions, higher amount of lead has been removed per gram of zeolite, where the highest values are recorded with addition of 0.06% of the Humistar ® solution. At lower lead concentration the addition of the Humistar ® solution increased removal for double, and increase of the Humistar ® solution concentrations increased removal for triple compared to the control suspension, respectively. The influence of the pH value on removal capacity in all experiments was negligible. The highest removal efficiency has been observed for lower lead concentrations with higher content of the Humistar ® solution. Based on the observed results it can be concluded that appearance of organic matter in the soil might increase removal efficiency during remediation of heavy metals using natural zeolites