Title Elektroanalitička svojstva folne kiseline na elektrodi izmijenjenoj različitim nanomaterijalima Title (english) Electroanalytical characteristics of folic acid on electrode modified with various nanomaterials Author Karla Stanko Mentor Biljana Nigović (mentor)Committee member Biljana Nigović (predsjednik povjerenstva)Committee member Ana Mornar Turk (član povjerenstva)Committee member Dubravka Vitali Čepo (član povjerenstva)Granter University of Zagreb Defense date and country 2019-03-27, Croatia Scientific / art field, BIOMEDICINE AND HEALTHCARE Abstract Folna kiselina, koja pripada skupini B vitamina, neophodna je za razvoj hematopoetskog sustava, rast i diobu stanica te brojne druge, izuzetno važne, biološke procese. Peroralno se primjenjuje u liječenju megaloblastične anemije, hepatobilijarnih bolesti i prevenciji defekta neuralne cijevi kod novorođenčadi. Kao suplement često je koriste oboljeli od Chronove bolesti jer je u njih zamijećen deficit folata. Ovim radom ispitivane su elektrokemijske karakteristike folne kiseline uporabom cikličke i pravokutnovalne voltametrije (SWV) u Britton-Robinson (BR) puferu različitih pH vrijednosti na nemodificiranoj GCE i GCE modificiranoj raznovrsnim nanomaterijalima. Cilj je bio istražiti njezino oksidacijsko ponašanje u svrhu razvoja nove elektroanalitičke metode za istovremeno određivanje folne kiseline i mesalazina, jednog od najkorištenijih lijekova u liječenju Chronove bolesti. BR pufer pH vrijednosti 6 iskazao se najprikladnijim zbog najveće vršne jakosti struje i izrazito pravilne definiranosti oksidacijskog pika koji se javlja pri potencijalu 0,85 V. Nadalje, modificiranjem površine GCE ustanovljeno je da nanesene suspenzije nanomaterijala u 0,5 %-tnoj otopini kitozana u 1 %-tnoj octenoj kiselini doprinose intenzivnijem odazivu analita. Najbolje performanse pokazale su višeslojne ugljikove nanocjevčice modificirane amino skupinama (MWCNT/NH2) i grafitom (MWCNT/grafit). Analizom smjese folne kiseline i mesalazina u BR puferu pH nastao je dodatan pik na oko 0,35 V oksidacijom mesalazina. MWCNT/NH2 (c=1,0 mg/mL) pokazao se kao optimalan nanomaterijal za modifikaciju GCE upotrijebljene za njihovu istovremenu detekciju. Pravokutnovalni voltamogrami otopine njihovih uzoraka dokazuju da je oksidacija mesalazina reverzibilna reakcija pri čemu se vidi povratni pik, dok se oksidacija folne kiseline odvija ireverzibilno. Utvrđeno je da su optimalni SWV parametri za simultano određivanje ovih dvaju analita frekvencija 100 Hz, amplituda pulsa 40 mV i porast potencijala 10 mV. Korelacijom vršnog potencijala i promjene pH došlo se do ovisnosti koje potvrđuju da protoni oslobođeni tijekom oksidacijskih reakcija obiju tvari ne utječu na kinetiku izmjene elektrona. Nadalje, nanošenjem sloja nanomaterijala volumena 3 μl cijepao se pik mesalazina, a nestabilnost u otopini uzora pokazao je sloj volumena 10 μl. Volumen nanomaterijala 5 μl određen je kao najprimjereniji jer daje dobro definirane voltametrijske odgovore i postojan je tijekom određenog broja mjerenja.
Abstract (english) Folic acid is one of the B vitamins group that has an integral part in developement of hematopoetic system, cell growth and proliferation, but also other very important biological processes. It is used per oral for treating megaloblastic anemia, hepatobiliary disorders and in preventing neural tube defects in infants. As a supplement it is often used by patients with Chron's disease since they have folate deficiency. This work examined electrochemical characteristics of folic acid in BR-buffer of different pH values on unmodified GCE and GCE modified with various nanomaterials using cyclic and square-wave voltammetry (SWV). The purpose was to investigate its oxidation in order to develop a new electroanalytical method for simultaneous determination of folic acid and mesalazine, one of the most used medication for Chron's disease. BR-buffer of pH value 6 showed to be the most suitable because of the greatest peak current and distinctly defined oxidation peak that appeared at 0,85 V. Furthermore, by modifying GCE surface it was found that suspensions of nanomaterials in 0,5 % chitosan solution in 1 % acetic acid contribute to more intensive analyte's response. The best performances gave multi-walled carbon nanotubes modified by amino group (MWCNT/NH2) as well as graphitized multi-walled carbon nanotubes (MWCNT/graphite) (c=0,5; 1,0 and 2,0 mg/mL). Analysis of folic acid and mesalazine in BR-buffer pH 6 resulted in an additional peak at approximately 0,35 V following mesalazine oxidation. MWCNT/NH2 (c=1,0 mg/mL) approved as optimal nanomaterial for modification of GCE used for their parallel detection. Square-wave voltammograms of samples solution prove that oxidation of mesalazine is a reversibile reaction during which a backward peak can be seen, while oxidation of folic acid goes irreversibly. It was noticed that optimal SWV parameters used for simultaneous determination of both analytes are frequency 100 Hz, puls amplitude 40 mV and potential step 10 mV. Correlation between peak potential and pH variation resulted in dependances that confirm that protons released during oxidation of both substances do not affect electron transfer kinetics. Moreover, applying nanomaterial layer of volume 3 μl resulted in mesalazine peak splitting, while volume of 10 μl indicated unstableness. Nanomaterial volume of 5 μl was set as the most convenient as it gives well defined voltammetric responses and proved to be stable during certain number of measurements.
Keywords
folna kiselina
mesalazin
ciklička voltametrija
pravokutnovalna voltametrija
elektroda modificirana nanomaterijalima
Keywords (english)
folic acid
mesalazine
cyclic voltammetry
square-wave voltammetry
nanomaterial-modified electrode
Language croatian URN:NBN urn:nbn:hr:163:352965 Study programme Title: Pharmacy Type of resource Text File origin Born digital Access conditions Open access Terms of use Created on 2021-09-07 14:37:29
