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Potentiometric determination of anionic surfactant using home-made FIA/SIA system
No full textRazvojem znanosti dolazi do sve veće potražnje za bržim i efikasnijim metodama analize tvari. Potreba za korištenjem što manje količine uzorka s velikom preciznošću analize u vrlo kratkom vremenu, dovela je do razvoja mikrofluidike. Analiza injektiranjem u protok (flow injection analysis, FIA) prva je moderna mikrofluidička metoda i definirana je kao analitička metoda za automatsku analizu tekućih uzoraka koja se zasniva na disperziji zone uzorka nastale injektiranjem uzorka u tok otopine nosača. Daljnim razvojem ove metode nastaje sekvencijska injekcijska analiza (sequential injection analysis, SIA ), mikrofluidička metoda čija je glavna karakteristika dvosmjerni neprekinuti tok uzorka. U ovom završnom radu korištena je navedena metoda kako bi se analizirale anionske površinski aktivne tvari pomoću screen-printed mikrosenzora. Površinski aktivne tvari ili tenzidi smanjuju površinsku napetost tekućina i sastoje se od hidrofilnog i hidrofobnog dijela. Koriste se u sredstvima za čišćenje kao i proizvodima za osobnu higijenu. Vrlo je važno kontrolirati njihovu količinu kako u proizvodima u kojima se nalaze tako i u otpadnim vodama zbog naše sigurnosti i sigurnosti okoliša.Rapid development of science demands faster and more efficient methods of matter analysis. The need for using smaller amounts of sample and bigger precision of analysis in shorter periods of time led to development of microfluidics. Flow injection analysis (FIA) is the first modern microfluidic method and it is defined as analytical method for automatic analysis of liquid samples. It is based on dispersion of sample zone that was made by injecting the sample in the carrier flow and detection of the wanted feature. Further development led to sequential injection analysis (sequential injection analysis, SIA), microfluidic method that uses two-way continuous flow. Described method was used in this bachelor thesis to analyze anionic surfactants. Surface active agents or surfactants lower surface tension of liquids. They consist of hydrophobic and hydrophilic end of the molecule. Surfactants are used in cleaning products and products for personal hygiene. It is very important to monitor their amount in products that we use and their presence in waste water for our own safety and the safety of our environment
Potentiometric PVC nanoparticles enriched surfactant sensor
No full textNovi potenciometrijski senzor za anionske tenzide pripremljen je na osnovi višestjenčanih ugljikovih nanocjevčica (MWCNT) koji su upotrebljene za imobilizaciju 1,3-didecil-2-metilimidazol tetrafenilborat (DMI-TPB) ionskog para kao ionofora u membrani. Istraživani senzor pokazao je Nernstovski odziv za dodecilbenzensulfonat i dodecilsulfat. Odziv je prikazan unutar 8-10 sekundi za svaku deseterostruku promjenu koncentracije u rasponu od 1 x 10-7 M do 1 x 10-3 M. Granice detekcije za DBS i DS su 1 x 10-6 i 2 x 10-7 M. Senzor daje stabilan potenciometrijski odziv, te pokazuje zadovoljavajuću selektivnost za DS. Glavna primjena senzora je bila u otkrivanju završnih točaka u potenciometrijskim titracijama anionskih tenzida. Hyamine 1622, heksadeciltrimetilamonijev bromid i cetilpiridinijev klorid su testirani kao potencijalni kationski titranti i svi su dali analitički upotrebljive titracijske krivulje s dobro definiranim točkama ekvivalencije. Operativni životni vijek opisanog senzora je oko 3 mjeseca.A new potentiometric anionic surfactant sensor was prepared based on multi-walled carbon nanotubes (MWCNTs) used for immobilisation of 1,3-didecyl-2-methylimidazolium tetraphenylborate (DMI-TPB) ion pair as ionophore in the membrane. The investigated sensor showed a Nernstian response for both dodecylbenzenesulphonate and dodecyl sulphate. It responded in 8-10 seconds for each ten-fold concentration change in the range of 1 x 10-7 M to 1 x 10-3 M. The detection limits for DBS and DS were 1 x 10-6 and 2 x 10-7 M, respectively. The sensor revealed a stable potentiometric response and exhibited satisfactory selectivity for DS. The main application of the sensor was in the end-point detection in potentiometric titrations of anionic surfactants. Hyamine 1622, hexadecyltrimethylammonium bromide and cetylpyridinium chloride were tested as potential cationic titrants, and all exhibited analytically usable titration curves with well-defined equivalence point. The operational life time of the sensor described amounted ca. 3 months
Hidrofilically modified silicones as dispersants in aqueous solutions
No full textCilj i svrha ovog diplomskog rada jest ispitati na koji način i u kojim uvjetima hidrofilno modificirani silikoni malih molarnih masa djeluju na svojstva suspenzija nanočestica i ZnO u vodenim otopinama. Korišteni su hidrofilno modificirani silikoni različitih proizvođača, Elkay® Silicones, Xiameter® Dow Corning. Silikoni su karakterizirani mjerenjem viskoznosti pri različitim koncentracijama i pH vrijednostima. Akustičkom spektroskopijom ispitano je kako silikoni utječu na stabilnost suspenzija nanočestica, a moguća adsorpcija na površini nanočestica testirana je metodom TGA/DSC (termogravimetrijska analiza/razlikovna pretražna kalorimetrija). Rezultati su pokazali da silikoni djeluju kao dispergatori na suspenzije nanočestica, odnosno pospješuju raspršenost suspenzije nanočestica. Metodički dio rada sadrži pripremu za nastavnu jedinicu pod naslovom "Silicij i silikati". Nastavni sat zamišljen je kao kombinacija frontalnog i grupnog rada uz izvođenje pokusa.The aim and purpose of this work is to examine how and under which conditions hydrophilically modified silicones of small molecular weight affect the nanoparticle suspension ( and ZnO) properties in aqueous solutions. The silicones of two different manufacturers, Elkay® Silicones, Dow Corning® Performance Products were used. They were characterized by viscosity measurements in broad concentration and pH ranges. Acoustic spectroscopy was used to explore on how the silicones affect the nanoparticle suspension stability and a possible adsorption on the surface of nano particles was tested using the TGA / DSC (thermogravimetry / differential scanning calorimetry). Results showed that silicones act as dispersants for the aqueous nanoparticle suspension. Methodical part of the work includes preparation for teaching unit entitled "Silicon and silicates". Lesson is designed as a combination of teacher`s frontal talk and group student`s work with experimentation
Phase transitions
No full textFazni prijelaz je spontani proces pretvorbe jedne faze u drugu a javlja se pri specifičnom tlaku temperaturi. Temperatura prijelaza (Ttrs) između dvije faze, na primjer, tekućine i krutine ili između konformacije proteina, je temperatura pri određenom tlaku na kojoj je molarna Gibbsova energija dviju faza jednaka, odnosno na kojoj su dvije faze u ravnoteži. Fazni prijelaz je prijelaz iz jedne faze u drugu fazu. Promjenom uvijeta u okolini poput temperature,tlaka ili magnetskog polja, tvari mijenjaju stanje u kojem se nalaze. Taljenje, isparavanje i pretvorba grafita u dijamant su primjeri fazne pretvorbe bez promjene kemijskog sastava tvari. Sve u prirodi ima tendenciju prijelaza u stanje niže molarne Gibbsove energije pri konstantnoj temperaturi i tlaku.Phase transition is a spontaneous process of conversion from one phase to another which occurs at specific temperature and pressure conditions. Transition temperature (Ttrs) between phases, for example, between solid and liquid phase, or between protein conformations, is a temperature at specific pressure when molar Gibbs energy is equal for both phases, or whenthose two phases are in equlibrium, respectively. Phase transition is a transition from one phase to another. Matter changes its state when exposed to change in external conditions like temperature, pressure or magnetic field. Melting, evaporation and conversion of a graphite into diamond are examples of phase conversions without changing the composition of matter. In nature, everything has a tendency of transition into lower molar Gibbs energy state at constant temperature and pressure
Determination of anionic surfactants with MBAS method
No full textTenzidi su površinski aktivne tvari koje smanjuju površinsku napetost tekućine. Smanjuju sile koje djeluju između dvije faze, čime se omogućuje nastajanje pjene, stvaranje vodene emulzije s tvarima s kojima se voda inače ne miješa, uljem i masnoćama. Tenzidi su glavni sastojci detergenata. Osim toga, koriste se kao emulgatori, omekšivači, sredstva za stvaranje suspenzija, za zaštitu od korozije, za dezinfekciju, kao rashladna sredstva, u sredstvima za gašenje požara, u kozmetici. Spektrofotometrijske metode za određivanje anionskih tenzida, poput MBAS metode (eng. Methylene Blue Active Substances), bazirane su na reakciji anionskog tenzida i kationske boje kao što je metilensko plavo. Tijekom ovog istraživanja, određene su koncentracije anionskih tenzida u tri uzorka otpadnih voda detergentske industrije, koristeći MBAS metodu. Rezultati su uspoređeni s rezultatima određivanja dobivenim dvije godine ranije, te su pokazali zadovoljavajuće slaganje.Surfactants are surface active agents that reduce the surface tension of liquids. They lower the forces between two phases which brings to formation of foam and aqueous emulsion with substances that water does not normally mix with, olis and fats. Surfactants are main ingredients of detergents. They are also used as emulgators, softeners, suspending agents, for corrosion protection, disinfection, refrigerants, extinguishing media, in cosmetics. Spectrophotometric methods for anionic surfactants determination, as Methylene Blue Active Substances method (MBAS), are based on reaction of anionic surfactant and cationic dye, as methylene blue. In this research, concentrations of anionic surfactants in three samples of detergent industry effluents were determined using MBAS method. The results were compared with results obtained two years earlier and showed satisfactory agreement
Development and characterization of optical sol-gel sensor for pH determination
No full textCilj ovoga diplomskog rada je pripraviti optički sol-gel senzor za mjerenje pH. Sol-gel struktura sintetizirana je kombiniranjem dviju prekursorskih molekula, tetraetoksisilana (TEOS), propiltrimetoksisilana (pTriMOS) u etanolu kao otapalu, a uz HCl kao katalizator. Unutar gel strukture su ugrađene molekule pH indikatora bromokrezol ljubičasto i bromokrezol zeleno i njihova kombinacija. Pripravljeni senzorski slojevi pokazuju gotovo identična svojstva kao i same otopine indikatora. Količina indikatorske boje utječe na apsorbanciju slojeva, što je više indikatora veća je apsorbancija i između količine indikatora i apsorbancije postoji linearna ovisnost. Kod slojeva je uočen efekt ispiranja boje iz gel strukture. Staklo je pokazano kao bolji nosač sol-gela u odnosu na PVC foliju.Pripremljeni senzorski slojevi mogu biti korišteni kao indikatori završne točke kod titriranja. U metodičkom djelu rada opisana je obrada teme kiselo-bazne reakcije za učenike drugog razreda srednje škole. Učenici bi prvo upoznali pojmove vezane za kiselobazne reakcije (neutralizacija, indikatori i titracije), a zatim bi samostalno izveli pokus i rješavali postavljene zadatke.The aim of thesis is to prepare optical sol-gel sensor for pH determination. Sol-gels are preparedfrom two precursors molecules, tetraetoxysilane (TEOS) and propyltrimethoxysilane (pTriMOS) inethanol as solvent and HCl solution as catalyst. Molecules of pH indicator dyes bromocresol purpleand bromocresol green and their combination are immobilised inside gel structure. Sensor layerswith pH dyes shows almost the same properties as pH dyes in solution. Amount of pH indicatordyes have influence on UV-Vis apsorbance, more dye in sensor layer gives higher apsorbance. Thisdependence is linear. Leaching effect was observed on sensor layers, some dye molecules came outof gel in water. Glass showed better properties for sol-gel sensor carrier than PVC foil. This sol-gelsensors can be used for determination of end point in titrations. In teaching part of this thesis thereis an interpretation of two high school chemistry lessons where students would learn about acidbasereactions. Students are taught the acid-base reactions, titrations and pH indicators in the firstlesson. The second one would be dedicated to student's practical work and solving chemistryproblems
Synthesis of metal-organic frameworks with zinc(II)
No full textMetaloorganske mreže su porozni materijali koji su građeni od anorganskih(metalni kationi) i organskih jedinica (ligandi). Razlikuju se od drugih poroznih materijala zato što imaju relativno male pore, mikro- i nanopore, zbog čega takvi materijali imaju veliku specifičnu površinu te po maloj gustoći, fleksibilnosti i dinamičnosti. U ovom radu opisana je priprava četiriju spojeva cinka(II) s organskim, aromatskim dikiselinama kaoligandima. Dobiveni spojevi su karakterizirani pomoću FT-IR spektroskopije i termogravimetrijske (TG) analize. Rezultati ispitivanja upućuju na mogućnost nastanka poroznih materijala, s molekulskom i kristalnom građom nalik na poznati MOF5 spoj. TG analiza ukazuje na različite omjere cinka i vezanog liganda koji se pojavljuju u sintetiziranim materijalima te na to da se njihova termička stabilnost povećava s većim brojem alifatskih skupina u lancu liganda. Metodički dio rada sadrži pripremu za nastavnu jedinicu pod naslovom Cink i njegovi spojevi te biološka uloga cinka. Dva nastavna sata su zamišljena kao kombinacija frontalnog i grupnog rada uz izvođenje pokusa.Metaloorganic frameworks are porous materials that are built from inorganic(metals) and organic units (ligands). They are different from other porous materials fortheir large surface areas and pores, low density, flexibility and dinamics. Synthesis andanalysis of four novel compounds with Zn(II) cation and organic, aromatic diacids asligands are described in the thesis. The prepared compounds were characterized by meansof FT-IR spectroscopy and thermogravimetric (TG) analysis. The obtained results indicatethat the porous material might be formed through described reactions and that theirmolecular and crystal structure could be similar to the structure of the well known MOF5compound. TG analysis indicates that zinc cation is bounde in different stochiometric ratiodepending on ligand used in a synthesis. Also, a thermal stability of the prepared complexcompounds increases as the number of atoms in the aliphatic chain becomes larger, i.e. asthe ligand was longer. In the teaching part of the thesis a lecture Zinc and his compoundsand biological functions of zinc has been prepared for high school students. Lesson wasdesigned as a combination of teacher's talk and students' group work with experiments
Pollution in Kastela Bay
No full textU radu je opisano antropogeno zagađenje Kaštelanskog zaljeva elementarnom živom, nekim teškim metalima te uranom i njegovim raspadnim serijama radionuklida. Opisana je živa i njezina toksičnost, promjene koje unos žive uzrokuje u organizmu te zdravstveni rizici za izloženu populaciju. Detaljnije je obrađena problematika povećane koncentracije metil-žive u Kaštelanskom zaljevu, što uključuje podatke o izmjerenim koncentracijama ove organske tvari u sedimentu i nekim morskim organizmima. Opisana je i distribucija žive u zagađenom morskom području kao i prijedlozi za zaštitu i unapređenje.The paper presents anthropogenic pollution in Kastela Bay, contaminated with elemental mercury, some heavy metals, uranium and its decay series radionuclides. It gives an overview of mercury and its toxicity; changes that mercury can cause when enters the organism and health risk for the exposed population. There is also a detailed description of the problem with higher methyl-mercury concentrations in Kastela Bay, where the details of measured concentrations of this organic matter in sediments and some marine organisms are listed. Also, the way of mercury distribution in a polluted marine area, as well as proposals for its protection and improvement are described
The Effect of Mechanical Mixing, Temperature and Citrate Concentration on the Calcium Oxalate Precipitation
No full textKalcijevi oksalati su kalcijeve soli oksalne kiseline i sastavni su dio gotovo svih bubrežnih kamenaca. Bubrežni kamenci posljedica su rasta kristala u urinarnom traktu, a gotovo 10% ljudi susretne se s tim problemom tijekom života. U medicinskom je rječniku proces nastajanja bubrežnih kamenaca poznatiji pod nazivom urolitijaza ili nefrolitijaza. Upravo se zbog te činjenice sve češće provode istraživanja kojima bi se u potpunosti objasnio mehanizam, uvjeti i moguća prevencija nastajanja bubrežnih kamenaca. Kalcijev oksalat kristalizira u tri hidratna oblika: termodinamički stabilan kalcijev oksalat monohidrat (vevelit, COM), metastabilan dihidrat (vedelit, COM) te trihidrat (kaoksit, COT) koji se rijetko pronalazi u kemijskom sastavu bubrežnih kamenaca. Eksperimentalno je pokazano da promjena temperature i koncentracije citrata može utjecati na taloženje kalcijeva oksalata te na morfologiju i veličinu nastalih kristala. Rezultati su obrađeni FTIR spektroskopijom, TG analizom i optičkom mikroskopijom.Calcium oxalates are calcium salts of oxalic acid and they are the most common constituents of kidney stones. Kidney stones are the result of a crystal growth in the urinary tract and almost 10% of population experience such problems during their lifetime. Medical term of this process is known as the urolithiasis or nefrolithiasis. There have been many studies conducted with the aim to understand and explain the mechanism, precipitation conditions and possible prevention of the stone formation. Calcium oxalate crystallizes in three hydrate forms: thermodynamically stable monohydrate (whewellite, COM), the metastable modification, dihydrate (weddellite, COD) and trihydrate (caoxite, COT) which is rarely found in the kidney stones. The experimental results showed that a temperature changes and a concentration of citrate can influence morphology and size of precipitated crystals. Calcium oxalate crystals were studied by the means of thermal analysis (TGA) and infrared (FT-IR) spectroscopy. The morphology of calcium oxalate crystals was studied using the optical microscope
Determination of cations in natural waters using electrophoresis on microchip with C4D detector
No full textKapilarna elektroforeza (engl. Capillary electrophoresis, CE) je vrlo učinkovita separacijska tehnika za kvantifikaciju različitih nabijenih specija. Elektroforeza na mikročipu (engl. Microchip electrophoresis, MCE) je minijaturizirana verzija CE. Alkalijske i zemnoalkalijske metale rutinski se prati u različitim uzorcima vode, koji su važni u industriji voda za piće i otpadnih voda industrije. MCE uređaj sa kapacitivno spregnutim beskontaktnim detektorom vodljivosti (engl. CCCCD, engl. Capacitively-Coupled Contactless Conductivity Detection C4D) uspješno je primijenjen za analizu nekoliko kationa, pojedinačno i u smjesi. Separacija je provedena na borosilikatnom mikročipu, duljine separacijskog kanala 4 mm. Kao pomoćni elektrolit (engl. background electrolyte, BGE) korištena je 0,5 M octena kiselina, pH = 2,5. Primijenjeni napon injektiranja iznosio je +0,7 kV, a napon separacije +1,4 kV. Istraživan je utjecaj sljedećih parametara na učinkovitost separacije: vrijeme injektiranja, napon injektiranja, vrijeme i napon separiranja. Ustanovljen je linearni odziv za svaki pojedini ispitivani kation, pojedinačno i u smjesi pomoću linearne regresije. Metoda je primijenjena kod određivanja kationa u vodi iz slavine, flaširanoj vodi i u kišnici. Metodički dio rada sadrži pripremu za nastavnu jedinicu Osnovna svojstva tekućina. Nastavni sat je zamišljen kao kombinacija frontalnog i grupnog rada sa pokusima. Grupnim radom nastoji se osamostaliti učenike, a pokusima im se nastoji približiti gradivo te potiče na razmišljanje i donošenje zaključaka.Capillary electrophoresis (CE) is a highly efficient separation technique for quantitation of different charged compounds. Electrophoresis on microchip (MCE) is a miniaturized version of the CE.Alkali and earthalkali metals were routinely monitored in a variety of aqueous samples important to several industries, such as drinking and waste water industries.In this investigations a MCE device with capacitively coupled contactless conductivity detection (engl. Capacitively-Coupled Contactless Conductivity Detection, CCCCD, C4D) has been successfully applied for analysis of several cations, individually and in mixture. The separation was carried out on a borosilicate microchip with the separation channel length of 4 mm. Acetic acid solution of the concentration 0.5 M has been used as a background electrolyte (pH = 2.5). The applied injection voltage was +0.7 kV and the separation voltage was +1.4 kV. The influence of the following parameters on the separation ability was investigated: injection time, injection voltage, separation time and separation voltage. The linear response region for each particular cation investigated, both single and in a mixture, has been determined using linear regression. The method was applied to determine cations in tap water, mineral water and rain water.In the teaching part of the thesis it is proposed a preparation lecture called The basic properties of liquids. Lesson is designed as a combination of frontal lectures and students group work with experiments. Aim of the group work is to achieve the independence of students, and experiments are helpfull for thinking about teaching materials and to make conclusions