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Prediction of pKa values of selected compounds present in valerian, Valeriana officinalis L.
No full textValerijana, Valeriana officinalis L., zelena je trajnica koja se koristi u liječenju različitih stanja i bolesti čovjeka još od antičke Grčke i Rima. Može narasti do 150 cm u visinu, listovi su najčešće smješteni na višim dijelovima biljke. Cvjetovi valerijane mogu biti bijeli ili ružičasti, dok je plod valerijane maleni oraščić veličine do 0,5 cm. U cijeloj biljci valerijane do sada je identificirano oko 150 spojeva, ali još uvijek nije u potpunosti utvrđeno njihovo djelovanje. Budući da spojevi još nisu u potpunosti istraženi, pretpostavka je da se djelovanje preparata od valerijane temelji na sinergističkom učinku pojedinih spojeva ove biljke. Valerijana se danas najčešće koristi kod problema s nesanicom te nervozom. pKa vrijednost je logaritamska vrijednost konstante disocijacije. Pomoću pKa vrijednosti može se odrediti ili modificirati ponašanje tvari koje nas zanima, a pKa se može odrediti eksperimentalno i računalno. U ovom radu, računalno je određena pKa odabranih spojeva valerijane te je utvrđena promjena sumarnog naboja i protoniranih stanja u ovisnosti o pH medija za svaki ispitani spoj.Valerian, Valeriana officinalis L., is a green perennial plant used in the treatment of various conditions and illnesses since ancient Greece and Rome. It can grow up to 150 cm in height, the leaves are usually in the higher part of the plant. Valerian flowers can be white or pink while the fruit is in the form of a little nut and has a size up to 0.5 cm. Around 150 different compounds have been discovered in the valerian plant, but their activity has not been fully elucidated yet. Since these compounds have not been fully investigated yet, the effect of the valerian preparations is assumed to be a result of synergistic effect of individual components of this plant. Nowadays, valerian is commonly used for insomnia and anxiety treatment. pKa value is the logarithmic value of the dissociation constant. pKa may help in determining or modifying the activity of studied compound, and is determined experimentally and computationally. In this thesis, pKa of selected compounds found in valerian was computationally determined. Also, net charges and protonation charges vs pH were analysed for chosen compounds
Sonochemical synthesis and characterization of ZrO2 nanoparticles
No full textNanočestice imaju široku primjenu zahvaljujući svojim dimenzijama (1 - 100 nm) i svojstvima. Jedna od učinkovitijih metoda njihove sinteze je sonokemijska sinteza. Cilj ovog rada je odrediti utjecaj trajanja sinteze, amplitude i trajanja pulsa ultrazvukom potpomognute sinteze na konačni omjer faza i veličinu kristalita nanočestica ZrO2. Za sintezu korišteni su ZrO(NO3)2 · xH2O i etilendiamin u vodenom mediju. U literaturnom pregledu opisan je ultrazvuk i sonokemijska sinteza, njezine sastavnice i mehanizam. Detaljno je opisana kavitacija, cirkonijev dioksid i njegove faze. FT-IR analiza prekursora (prije kalcinacije) ne pokazuje prisutnost OH skupine hidroksida i upućuje na nastanak hidratiziranih oksida. Nakon kalcinacije može se uočiti maksimum pri 504 cm-1 koji pripada istezanju Zr - O. FT-IR analizom utvrđeno je da je kvalitativni sastav prekursora (i kalciniranih uzoraka) jednak i ne ovisi o parametrima sinteze. Kvantitativna PXRD analiza pokazuje prisutnost monoklinske i tetragonske faze ZrO2 u uzorcima nakon kalcinacije. Povećani udio monoklinske faze detektiran je u uzorcima sonificiranim do 15 min i uzorcima s sonificiranim pulsom ultrazvuka u trajanju od 1 i 2 s. Čista tetragonska faza nastaje isključivo u uzorku sonificiranom 30 min. Utjecaj na veličinu kristalita nije zapažen. Usprkos prisutnosti dviju faza TEM analiza pokazuje sličnost u veličinama kristalitaDimensions and properties of nanoparticles enables their wide application. Sonochemical synthesis is effective method for their preparation. The aim of this work is to determine the influence of synthesis duration, amplitude and pulse duration of ultrasound assisted synthesis on the final phase ratio and crystallite size of ZrO2 nanoparticles. ZrO(NO3)2 · xH2O and ethylenediamine were used for synthesis in an aqueous media. In theoretical part we discussed ultrasound, sonochemical synthesis, its components and mechanism. Cavitation, zirconia and its phases were discussed. FT-IR analysis of precursors doesn't show presence of hydroxide OH group and refers to synthesis of hydrated oxides. After calcination peak at 504 cm-1 is present (Zr - O stretching). FT-IR analysis shows same qualitative composition of precursors (and calcinated samples) so it doesn't depend on synthesis parameters. Quantitative PXRD analysis show presence of monoclinic and tetragonal ZrO2 phases in samples after calcination. Increased share of monoclinic phase was detected in samples sonicated up to 15 min and samples sonicated with ultrasound pulse of 1 - 2 s. Pure tetragonal phase is present only in a sample sonicated for 30 min. Influence on crystallite size was not detected. Even though there are two phases present, TEM analysis shows similar crystallite size
Development and optimization of the new potentiometric sensor for determination of promethazine
No full textPrometazin hidroklorid (PM) je derivat fenotiazina koji se koristi kao antagonist H1-receptora, lokalni anestetik, antiemetik, sedativ, antialergijsko sredstvo, antikoronavirusno sredstvo i geroprotektor. Može uzrokovati štetne učinke kod ljudi, poput endokrinih, srčanih i reproduktivnih promjena, stoga je iznimno važno razviti nove metode za njegovo određivanje u komercijalnim formulacijama i biološkim uzorcima. Cilj ovog rada je razvoj i optimizacija potenciometrijskog senzora za određivanje PM temeljenog na ionskom paru kationa prometazina i tetrafenilboratnog aniona (PM-TPB) kao elektroaktivnom materijalu, koji je ugrađen u tekuću membranu elektrode. Kako bi se dobila optimalna membrana za potenciometrijski senzor, ispitan je utjecaj vrste plastifikatora i udjela elektroaktivnog materijala na karakteristike PM-TPB senzora. Utvrđeno je da optimalna membrana PM-TPB senzora u svom sastavu ima 66% o-nitrofenil oktil etera kao plastifikatora, 33% polivinil klorida i 1% elektroaktivnog materijala. Senzor je pokazao nagib od 56,2 mV po dekadi aktiviteta, široko mjerno područje od 6,17∙10-7 do 5,0∙10-3 mol/dm3 i nisku granicu detekcije od 1,25∙10-7 mol/dm3.Promethazine hydrochloride (PM) is a phenothiazine derivative used as an H1-receptor antagonist, local anesthetic, antiemetic, sedative, antiallergic agent, anticoronavirus agent and geroprotector. It can cause adverse effects in humans, such as endocrine, cardiac and reproductive changes, so it is extremely important to develop new methods for its determination in commercial formulations and biological samples. The aim of this work is the development and optimization of a potentiometric sensor for the determination of PM based on the ion pair of promethazine cation and tetraphenylborate anion (PM-TPB) as an electroactive material, which is embedded in the liquid membrane of the electrode. In order to obtain an optimal membrane for the potentiometric sensor, the influence of the type of plasticizer and the percentage of electroactive material on the characteristics of the PM-TPB sensor was examined. It was determined that the optimal PM-TPB sensor membrane has 66% of o-nitrophenyl octyl ether as a plasticizer, 33% of polyvinyl chloride and 1% of electroactive material. The sensor showed a slope of 56.2 mV per decade of activity, a wide measurement range from 6.17∙10-7 to 5.0∙10-3 mol/dm3 and a low detection limit of 1.25∙10-7 mol/dm3
Synthesis of simple nanocrystalline oxide-based perovskites comprising transition metals and lanthanides
No full textKako je u današnje vrijeme porasla potreba za novim materijalima s velikim izborom svojstava, istraživanje perovskita uvelike je poraslo. Zbog velike mogućnosti dopiranja ovih spojeva, perovskiti su se pokazali kao odlični kandidati za veliki broj novih tehnologija. U ovom diplomskom radu sintetizirani su nanokristalni oksidni perovskiti na bazi prijelaznih metala i lantanoida. Cilj uvođenja novih elemenata u sustav je povećati konfiguracijsku entropiju sustava kako bi se povećala njihova stabilnost te kako bi spojevi dobili nova svojstva. Svi navedeni perovskiti sintetizirani su modificiranom citratnom sol-gel metodom pri istim uvjetima, te su svi spojevi prošli jedan korak kalcinacije pri 600 °C u struji zraka s temperaturom zagrijavanja od 2 °C/min. Dobivani spojevi zatim su okarakterizirani rentgenskom difrakcijom na prahu (PXRD), termogravimetrijskom analizom (TGA/DSC), UV/VIS spektroskopijom i analizom specifične površine i eventualne poroznosti Brunauer-Emmett-Teller (BET) metodom.As the need for new materials with a wide variety of properties has increased nowadays, perovskite research has grown greatly. Due to the high possibility of doping these compounds, perovskites have proven to be excellent candidates for a large number of new technologies. In this thesis, nanocrystalline oxide perovskites based on transition metals and lanthanides were synthesized. The goal of introducing new elements into the system is to increase the configurational entropy of the system in order to increase their stability and to give the compounds new properties. All the mentioned perovskites were synthesized by a modified citrate sol-gel method under the same conditions, and all compounds underwent one step of calcination at 600 °C in an air flow with a heating temperature of 2 °C/min. The obtained compounds were further characterized by the X-ray powder diffraction (PXRD), thermogravimetric analysis (TGA/DSC), UV/VIS spectroscopy, and Brunauer-Emmett-Teller (BET) analysis
Study of the solvent effect on the application of Phytolacca sp. L. as acid-base indicator
No full textIndikator je sredstvo koje ukazuje na stanje ili promjene stanja nekog sustava, a u kemiji se koristi kao tvar koja promjenom boje pokazuje prisutnost neke druge tvari te kako bi se odredila pH vrijednost medija. Konvencionalni kiselo-bazni indikatori se pripremaju u kemijskom laboratoriju, primjeri takvih indikatora su metil crveno, lakmus papir i fenolftalein. Jeftinija i manje štetna varijanta indikatora su alternativni odnosno prirodni kiselo-bazni indikatori. Primjeri takvih indikatora su kurkuma, crveni kupus, grožđe, luk i dr. U ovom radu ispitani su plodovi vinobojke (Phytolacca sp.) kao kiselo-bazni indikator. Vinobojka ima bobice tamno ljubičaste boje, što sugerira na prisutnost betacijanina, te se pretpostavlja da ima potencijal kao kiselo-bazni indikator. U radu su pripremljeni i ispitani indikatori od suhih i svježih zrelih plodova vinobojke u hladnoj i vrućoj vodi, metanolu, acetonu i etanolu. Prema dobivenim rezultatima, svježa vinobojka daje vizualno dojmljivije rezultate u odnosu na suhu vinobojku, a obje daju najintenzivniju promjenu pri pH = 14. Od otapala se metanol pokazao najpogodnijim za pripremu ovih indikatora, iako su i ostala korištena otapala pokazala određeni potencijal.Indicator shows the state or changes of the state of a system, and in chemistry an indicator shows the presence of another substance by changing colour and is used to determine the pH value of a medium. Conventional acid-base indicators are prepared in a chemical laboratory, examples of such indicators are methyl red, litmus paper and phenolphthalein. A cheaper and less harmful version of indicators are alternative or natural acid-base indicators. Examples of such indicators are turmeric, red cabbage, grape, onions, etc. In this thesis, the fruit of the pokeweed (Phytolacca sp.) were tested as an acid-base indicator. Pokeweed has dark purple berries hence it is assumed that they contain betacyanins and could be used as an acid-base indicator. So, in this work, indicators made form dry and fresh ripe pokeweed berries with cold and hot water, methanol, acetone and ethanol were prepared and tested. According to obtained results, fresh pokeweed showed visually more impressive results, and fresh and dried pokeweed had the most intensive colour change at pH = 14. Of all used solvents, methanol seems to be the best for preparation of these indicators, though other solvents showed potential too
Preparation and Modification of Carbon Quantum Dots from Citric Acid: The Application in Metal Ions Detection
No full textUgljikove kvantne točke (CQD) inovativna su i efektivna forma fotoluminiscentnih ugljičnih nanomaterijala. Njihova kemijska stabilnost, niska toksičnost, biokompatibilnost, topljivost i fotoluminiscencija predstavljaju veliki potencijal primjene u biomedicinskim istraživanjima i nanotehnologiji. CQD su veličine obično do 10 nm i sastoje se od ugljične jezgre sa sp3 hibridiziranim i nešto manje sp2 hibridiziranim ugljikovim atomima, ali s obzirom na stajanje i skladištenje mogu biti veličine do 60 nm. Prednost CQD je sposobnost dopiranja heteroatomima u strukturu ili dodatkom funkcionalnih grupa na površinu, kako bi se povećalo kvantno iskorištenje (QY) i sposobnost interakcija s drugim biološkim materijalima. CQD se stoga mogu koristiti u detektiranju različitih kemijskih specija, pa tako i metalnih iona i biomolekula. Postoje dva pristupa sinteze CQD; "top - down" i "bottom - up". Glavna prednost "bottom - up" pristupa jest namještanje optimalnih uvjeta sinteze i biranje optimalnih kemijskih prekursora, ovisno o željenoj primjeni. Tako su u ovom radu sintetizirane CQD iz limunske kiseline i aminokiselina; Leucin (Leu), Triptofan (Trp), Arginin (Arg), Alanin (Ala) i Histidin (His) kao izvor dušika. U usporedbi s blank uzorkom, N - dopirane CQD pokazale su znatno viši QY pa je tako uzorak CQD@Leu pokazao selektivan odziv na Fe3+ ione u probama gdje se gledalo smanjenje intenziteta fotoluminiscencije. Dobiveni rezultati su pokazali potencijalnu primjenu CQD u detekciji metalnih iona, u poljima biomedicine, analitičke kemije i okolišu.Carbon quantum dots (CQD) are new and efficient form of photoluminescent carbon nanomaterials. The CQDs excellent chemical and optical properties are chemical stability, low toxicity, biocompatibility, solubility and photoluminescence. The CQD are mostly used in biomedicine and in nanotechnology fields. CQD are usually in size of 10 nm, but depending on the storage time, size can vary up to 60 nm. The CQD contain of carbon core mainly of sp2 and less of sp3 hibridized carbon atoms. One of the many advantages od CQD is the possibility of doping with heteroatoms which can lead to the heteroatom incorporation within the structure or by adding functional groups to the surface of the particles to increase quantum yield (QY) and to enhance possible interactions of CQD with other biomaterials. Hence, CQD can be also used in sensing of different chemical species, metal ions and biomolecules. There are two different methods for CQD synthesis, "top - down" and "bottom - up" approaches. The main advantages of "bottom - up" approach are applying optimal chemical operating conditions and selection of chemical precursors. In this paper, CQD from citric acid and amino acids as N - dopant; Leu, Trp, Arg, Ala i His, have been synthesized. Compared to pure CQD (blank), N - doped CQD have shown higher QY. A sample CQD@Leu has shown a selective response to Fe3+ ions when tested changes in photoluminescence intensity. Results have shown potential application of N - doped CQD in metal ion sensing, biomedicine, analitical chemistry and environmen
Influence of photoperiod on antioxidant activity of industrial hemp (Cannabis sativa L. subsp. sativa)
No full textIndustrijska konoplja (Cannabis sativa L. subsp. sativa) je prilagodljiva biljka koja se iz Azije raširila po cijelom svijetu. Nutritivna svojstva duguje svom sastavu u koji ulaze ugljikohidrati, proteini, masti, minerali, vitamini i antioksidansi zbog čega se sve više koristi u ljudskoj prehrani. U ovom radu je ispitivan utjecaj različitih fotoperioda na antioksidativnu aktivnost industrijske konoplje kultivara Finola. Veći sadržaj ukupnih topljivih polifenola, antioksidativne aktivnost i celuloze uočeni su u uzorcima uzgajanim na fotoperiodu 20/4 dok je veći sadržaj produkata lipidne peroksidacije, askorbinske kiselina i proteina izmjeren u uzorcima uzgajanim na fotoperiodu 24/0. Fotoperiod 16/8 se pokazao kao najpovoljniji omjer osvjetljenja i tame za učinkovite fotokemijske reakcije. Dobiveni rezultati upućuju kako duljina svjetlosti ima značajan utjecaj na antioksidacijski odgovor industrijske konoplje.Industrial hemp (Cannabis sativa L. subsp. sativa) is an adaptable plant that has spread throughout the world from Asia. It owes its nutritional properties to its composition, which includes carbohydrates, proteins, fats, minerals, vitamins and antioxidants, which is why it is used more and more in human nutrition. This study examined the effect of different photoperiods on the antioxidant activity of industrial hemp cultivar Finola. Higher content of total soluble polyphenols, antioxidant activity and cellulose were observed in samples grown on photoperiod 20/4, while higher content of lipid peroxidation products, ascorbic acid and protein was measured in samples grown on photoperiod 24/0. Photoperiod 16/8 was proven to be the most favorable light-dark ratio for efficient photochemical reactions. The obtained results indicate that the length light has significant influence on the antioxidant response of industrial hemp
Cyclooxygenase 2 (COX-2) inhibitors
No full textCiklooksigenaza-2 (engl. Cyclooxygenase-2, COX-2) je enzim koji se pojavljuje u bolnim i upaljenim tkivima, dok je u zdravim tkivima uglavnom neaktivan. To je enzim koji katalizira nastanak prostanoida (prostaglandina, tromboksana i prostaciklina), spojeva koji povećavaju upalnu reakciju u organizmu. Kako bi se bol i upala umanjile koriste se različiti inhibitori ovog enzima. Među prvima su se razvili neselektivni inhibitori koji su osim COX-2 inhibirali i rad vrlo sličnog enzima, ciklooksigenaze-1 (engl. Cyclooxygenase-1, COX-1). Kasnija istraživanja su se usredotočila na pronalazak selektivnih inhibitora koji će inhibirati samo rad COX-2. Međutim, takvi su inhibitori pokazali velik broj neželjenih nuspojava. Novija istraživanja se usmjeravaju na pronalazak adekvatnih inhibitora prirodnog porijekla jer oni izazivaju značajno manji broj nuspojava. Također, neki od inhibitora COX-2 pokazali su značajna antikancerogena svojstva zbog čega se ispituju u kombinacijama s raznim kemoterapeuticima.Cyclooxygenase-2 (COX-2) is an enzyme that occurs in painful and inflamed tissues, while it is mostly inactive in healthy tissues. It is an enzyme that catalyses the production of prostanoids (prostaglandins, thromboxanes and prostacyclins), compounds that increase the body's inflammatory response. Various inhibitors of this enzyme are used to reduce pain and inflammation. First developed inhibitors were non-selective inhibitors that, in addition to COX-2, inhibited the work of a very similar enzyme, cyclooxygenase-1 (COX-1). Subsequent research has focused on finding selective inhibitors that will only inhibit COX--2 activity. However, such inhibitors have shown a large number of unwanted side effects. Recent research focus on finding adequate inhibitors of natural origin because they have significantly reduced side effects. Also, some of the COX-2 inhibitors have shown significant anticancer properties which is why they are being tested in combination with various chemotherapeutics
Study of the application of (sub)tropical fruit as acid-base indicator
No full textZnanstvenici u znanstveno-istraživačkim laboratorijima često zaboravljaju na potencijalne prirodne kiselo-bazne indikatore zbog učestalosti korištenja sintetiziranih. Istraživanjem voća i povrća kao potencijalnih kiselo-baznih indikatora te usvajanjem činjenica o istima, kemija se usko povezuje sa svakodnevnim životom, ali je se približava i laicima koje se upoznaje sa znanošću. Obrada i proučavanje pojmova poput pH vrijednosti, kiselina, baza i indikatora se ponekad automatski povezuje sa sintetskim indikatorima, koji često mogu biti nepraktični. Stoga je cilj ovog rada ispitivanje potencijala primjene odabranog biljnog materijala kao kiselo-baznog indikatora. U tu je svrhu korišteno i ispitano odabrano (sup)tropsko voće u kombinaciji s određenim otapalima (aceton, voda, etanol, metanol), a ispitivanje je provedeno odmah po pripremi indikatora i nakon 24 h stajanja indikatora na sobnoj temperaturi. Rezultati istraživanja pokazuju velik potencijal korištenja određenih vrsta (sup)tropskog voća u pripremi prirodnih kiselo-baznih indikatora. Od ispitanog biljnog materijala, kao vizualno najdojmljiviji istaknuli su se indikatori pripremljeni od manga i nara.Scientists in research laboratories often forget about potential natural acid-base indicators due to the frequency of using synthesised ones. By researching fruit and vegetables as potential acid-base indicators and by learning the facts about them, chemistry is closely connected with everyday life, but it is also brought closer to laymen familiarising them with science. Research and studies of concepts such as pH value, acid, base and indicators are sometimes automatically associated with synthetic indicators, which can often be impractical. Therefore, this work examines the potential of using the plant material as an acid-base indicator. For this purpose, selected (sub)tropical fruits were used and tested in combination with certain solvents (acetone, water, ethanol, methanol), the test was carried out immediately after the indicator preparation and 24 hours after preparation. The research results show great potential of using certain types of (sub)tropical fruits to prepare natural acid-base indicators. Indicators prepared from mango and pomegranate (of all the examined plant materials) stood out as the most visually impressive
Determination of thiabendazole using sensor with functionalized carbon nanotubes
No full textTiabendazol (TBZ) je derivat benzimidazola koji ima široku primjenu kao fungicid. Koristi se za suzbijanje bolesti voća i povrća kao što su plijesan, trulež, plamenjača i mrlje. Veliku primjenu ima kod banana i agruma za održavanje svježine te kao komponenta voska koji se nanosi na voće. Sukladno navedenom, najviše se zadržava u kori voća. TBZ ima nisku toksičnost ali je klasificiran kao kancerogen kod većih doza te može izazvati poremećaj u radu štitnjače. U ljudskom organizmu prilikom konzumacije voća i povrća tretiranih tiabendazolom, sukladno postojećim propisima, nakuplja se koncentracija TBZ nedovoljna da izazove rak. Najčešće korištene metode za određivanje TBZ su kromatografske metode, Ramanova spektroskopija, UV/Vis spektrofotometrija, fosforometrija i imunotest. Većina navedenih metoda iziskuje skupu opremu, korištenje velikih količina organskih otapala te komplicirane procedure i pripreme uzoraka. S obzirom na navedeno, korištenje ionsko selektivnih elektroda (ISE) je dobra alternativna metoda zbog jednostavnosti njihove pripreme i primjene te dobrih analitičkih preformansi. Takve elektrode najčešće sadrže tekuću membranu koja sadrži senzorski materijal, plastifikator i polivinil klorid. Glavni nedostatak elektroda s tekućom membranom je mogućnost istjecanja senzorskog materijala. Navedeni nedostatak dovodi do promjena karakteristika samog senzora, a time i smanjenja radnog vijeka senzora. Kako bi se izbjegli navedeni nedostatci, moguće je koristiti senzore s čvrstim kontaktom (engl. solid state) ili modificirati sastav membrane koristeći senzorske materijale koji su manje topljivi u vodi. Nanomaterijali bazirani na ugljiku su se pokazali vrlo pogodnim za tu svrhu. Modifikacija senzorskog materijala s višestjenčanim ugljikovim nanocjevčicama (engl. multi-walled carbon nanotubes, MWCNT) rezultira boljim odzivnim karakteristikama senzora, manjim ispiranjem senzorskog materijala iz membrane te manjim šumom signala. MWCNT se mogu kovalentno modificirati zadržavajući svoja inicijalna svojstva te na taj način formirati hibridni senzorski materijal. Direktna potenciometrijska mjerenja, koristeći senzore s čvrstim kontaktom i tekućom membranom modificiranom MWCNT, imaju veliki potencijal za određivanje TBZ zbog jednostavnosti metode te jednostavne primjene, točnosti i dugotrajnosti takvih senzora. U ovom radu korišten je novi potenciometrijski senzor s čvrstim kontaktom i tekućom membranom za određivanje TBZ. Kao senzorski materijal novog senzora korišten je hibridni materijal temeljen na MWCNT modificiranim sulfatnom skupinom i TBZ ionom. Senzor je pokazao Nernstovski odziv na TBZ (60,4 mV/dekada aktiviteta) u mjernom području između 8.6 ∙ 10-7 i 1.0 ∙ 10-3 M. Granica detekcije za TBZ je bila 6.2 ∙ 10-7 M dok je vrijeme odziva senzora na TBZ bilo 8 s. Tijek signala (engl. signal drift) iznosio je 1.7 mV/h. Mjerno pH područje senzora bilo je između 2 i 4, što nije predstavljalo ograničenje za korištenje senzora jer je TBZ topiv tek pri pH 2.6. Senzor je uspješno primijenjen za izravno potenciometrijsko određivanje TBZ-a u čistim otopinama te u složenim realnim uzorcima (kora naranče, limuna, banane, klementine i limete). Točnost senzora potvrđena je metodom standardnog dodatka. Vrijeme trajanja senzora, uz svakodnevno korištenje bilo je oko tri mjeseca.Thiabendazole (TBZ) is a benzimidazole derivative that is widely used as a fungicide. It is used to control fruit and vegetable diseases such as mold, rot, blight and spots. It is widely used in bananas and citrus fruits to maintain freshness and as a component of wax that is applied to the fruit. According to the above, it is mostly retained in the fruit peel. TBZ has low toxicity, but it is classified as a carcinogen at higher doses and can cause thyroid disorders. In the human body, when consuming fruits and vegetables treated with TBZ, in accordance with existing regulations, a concentration of TBZ will be insufficient to cause cancer. The most commonly used methods for TBZ determination are chromatographic methods, Raman spectroscopy, UV/Vis spectrophotometry, phosphorimetry and immunoassay. Most of the mentioned techniques require expensive equipment, the use of large amounts of organic solvents, and complicated procedures and sample preparations. Considering the above, the use of ion selective electrodes (ISE) is a good alternative method due to the simplicity of their preparation, application and good analytical performance. Such electrodes usually contain a liquid membrane containing sensor material, plasticizer and polyvinyl chloride. The main disadvantage of electrodes with a liquid membrane is the possibility of leakage of the sensor material. The aforementioned deficiency leads to changes in the characteristics of the sensor itself and shortened lifetime of the sensor. In order to avoid the mentioned shortcomings, it is possible to use solid-state sensors or to modify the composition of the membrane using sensor materials that are as less soluble as possible in water. Carbon-based nanomaterials have proven to be very suitable for this purpose. Modification of the sensor material with multi-walled carbon nanotubes (MWCNT) results in better response characteristics of the sensor, less leaching of the sensor material from the membrane and less signal noise. MWCNTs can be covalently modified while retaining their initial properties, thus forming a hybrid sensor material. Direct potentiometric measurements, using sensors with a solid contact and a liquid membrane modified with MWCNT, have great potential for TBZ determination due to the simplicity of the method and the simple application, accuracy and durability of such sensors. In this work, a new potentiometric solid-state sensor with a liquid membrane was used to determine TBZ. A hybrid material based on MWCNT modified with sulfate group and TBZ ion was used as the sensor material of the new sensor. The sensor showed a Nernstian response for TBZ (60.4 mV/decade of activity) in the measuring range between 8.6 ∙ 10-7 and 1.0 ∙ 10-3 M. The detection limit for TBZ was 6.2 ∙ 10-7 while the response time of the sensor for TBZ was 8 s. The signal drift was 1.7 mV/h. The measuring pH range of the sensor was between 2 and 4, which was not a limitation for the use of the sensor because TBZ is soluble only at pH 2.6. The sensor was successfully applied for direct potentiometric determination of TBZ in pure solutions and in complex real samples (peel of orange, lemon, banana, clementine and lime). The accuracy of the sensor was confirmed using the standard addition method. The lifetime of the sensor, with daily use, was approximately three months