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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The development of graphene oxide sheet- and polyanilino-immunosensor systems for lipoarabinomannan (LAM) tuberculosis biomarker

Wilson, Lindsay Robin January 2017 (has links)
Philosophiae Doctor - PhD / Tuberculosis (TB) is an infectious disease with adverse effect on a global scale. The disease is one of the major causes of death in sub-Saharan Africa. Nearly 70% of TB-infected persons are co-infected by the human immunodeficiency virus (HIV). About 50% of TB/HIV patients are smear negative and up to 28% are sputum scarce, which is a significant problem in South Africa since sputum smear microscopy is the most widely used diagnostic test for TB. The detection of Mycobacterium tuberculosis (MTB) and resistance to the TB drug rifampicin (RIF) are the basis of the GeneXpert MTB/RIF protocol. The GeneXpert MTB/RIF is an automated nucleic acid amplification technique for detecting the DNA that originates from MTB. However, low sensitivity and low concentrations of MTB for DNA amplification are a serious issue associated with the protocol. Therefore, other TB diagnostic methods, such as the ones involving biochemical markers of TB, are becoming very important. / 2020-08-31
2

Selective Determination of Uric Acid in the Presence of Ascorbic Acid at Screen-Printed Carbon Electrode Modified with Electrochemically Pretreated Carbon Nanotube

Lin, Liang-Shian 02 September 2010 (has links)
none
3

CYCLIC VOLTAMMETRIC DETERMINATION OF 17-α-ETHINYL ESTRADIOL ON DISPOSABLE SCREEN-PRINTED CARBON ELECTRODES

Qian, Zepeng 12 August 2019 (has links)
No description available.
4

Voltametrie s předřazenou extrakcí jako nový přístup pro rychlé stanovení formaldehydu v dřevěných výrobcích / Voltammetry with Preliminary Extraction as a New Approach for Rapid Determination of Formaldehyde in Wood-Based Products

Dvořák, Pavel January 2020 (has links)
The aim of the presented Diploma Thesis was to develop a new method for the indirect determination of formaldehyde in wood-based products using gas-diffusion microextraction coupled with electrochemical detection on unmodified screen-printed electrodes (MLEM-SPCE). Formaldehyde released from the sample is derivatized using an acetylacetone reagent present in an acceptor solution. The product of derivatization of formaldehyde with acetylacetone is 3,5-diacetyl-1,4-dihydrolutidine (DDL) which forms a selective oxidation voltammetric peak at a potential of 0.4 V. Detection and quantification limits of 0.57 mg kg−1 and 1.89 mg kg−1 , respectively, were obtained, together with intra- and inter-day precision below 10% (as relative standard deviation, RSD). The developed methodology was applied to determine formaldehyde content in seven samples. Similar results were obtained from the European standard method EN 717-3 with a significant reduction of total analysis time. The developed method MLEM-SPCE, which combines the use of a new sample preparation procedure for volatile compounds with the firstly introduced determination of formaldehyde (as the derivative product DDL) on unmodified SPCEs, proves to be a promising alternative for the determination of formaldehyde in wood-based products and other samples.
5

Development of Schiff base electrochemical sensors for the evaluation of polycyclic aromatic hydrocarbons in aqueous medium

Ward, Meryck January 2017 (has links)
Philosophiae Doctor - PhD / A novel monomer (N,N'-Bis-(1H-pyrrol-2-ylmethylene)-benzene-1,2-diamine-BPPD) was derived from the condensation reaction between o-phenylenediamine and a pyrrole derivative. The monomer was polymerized electrochemically to produce the new polymer material - polymerized(N,N'-Bis-(1H-pyrrol-2-ylmethylene)-benzene-1,2-diamine) PBPPD. This novel polymer material was deposited at the surface of a screen-printed carbon electrode, as a thin film, in the development of chemical sensors for the detection of polycyclic aromatic hydrocarbons (PAHs). The monomer material was characterized in terms of its optical (spectroscopy) and thermal properties. The polymer material was characterized in terms of its surface morphology and its redox electrochemistry. Fourier transform infrared spectroscopy (FTIR) was used to confirm the azomethine bond formation during the condensation reaction of an aldehyde and primary amine derivative. / 2020-08-31
6

Voltametrické a amperometrické stanovení homovanilové, vanilmandlové a 5-hydroxy-3-indoloctové kyseliny / Voltammetric and amperometric determination of homovanillic, vanillylmandelic, and 5-hydroxyindole-3-acetic acid

Němečková, Anna January 2020 (has links)
Presented dissertation thesis is focused on the development of electrochemical methods for the determination of three important tumour biomarkers, namely homovanillic acid (HVA), vanillylmandelic acid (VMA), and 5-hydroxyindole-3-acetic acid (5-HIAA). First part of the study is focused on electrochemical behaviour of these analytes in batch arrangement using differential pulse voltammetry (DPV) at screen-printed carbon electrodes (SPCEs). It has been proved that presented method is sufficiently sensitive for monitoring above mentioned analytes. Moreover, it can be used for determination of HVA and VMA in mixture. Obtained limits of detection (LODs) were 0.24 µmol·L-1 for HVA, 0.06 µmol·L-1 for VMA, and 0.12 µmol·L-1 for 5-HIAA. The requirements to speed up the analysis and at the same time to reduce its price initialized our study of the determination of tested biomarkers in flow systems. Firstly, flow injection analysis with amperometric detection was investigated for the determination of all three biomarkers at the same SPCE, and then an analogous determination of structural more similar pair, HVA and VMA, was performed at a boron doped diamond electrode (BDDE). Obtained LODs of optimized methods were as follows: at SPCE 0.07 µmol·L-1 for HVA, 0.05 µmol·L-1 for VMA, and 0.03 µmol·L-1 for 5-HIAA,...
7

Voltametrijske metode zasnovane na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala za određivanje vodonik-peroksida u odabranim uzorcima / Voltammetric methods based on the application of simple and contemporary carbonaceousmaterials-based electrodes/sensors for the determination of hydrogen-peroxide in the selected samples

Anojčić Jasmina 22 November 2018 (has links)
<p>Cilj&nbsp; ove&nbsp; doktorske&nbsp; disertacije&nbsp; je&nbsp; bio&nbsp; razvoj&nbsp; brzih&nbsp; i&nbsp; pouzdanih&nbsp; voltametrijskih&nbsp; metoda zasnovanih na primeni jednostavnih i savremenih elektroda/senzora na bazi ugljeničnih materijala (ugljenične&nbsp; paste&nbsp; napravljene&nbsp; od&nbsp; grafitnog&nbsp; praha&nbsp; i&nbsp; parafinskog&nbsp; ulja&nbsp; i&nbsp; &scaron;tampanih&nbsp; ugljeničnih elektroda)&nbsp; za&nbsp; određivanje&nbsp; H <sub>2</sub>O<sub>2 </sub>u&nbsp; odabranim&nbsp; složenim&nbsp; model&nbsp; i&nbsp; realnim&nbsp; uzorcima.&nbsp; U&nbsp; tu&nbsp; svrhu, ispitana je primenljivost različitih radnih elektroda. Amperometrijska&nbsp; metoda&nbsp; zasnovana&nbsp; na&nbsp; elektrodi&nbsp; od&nbsp; ugljenične&nbsp; paste&nbsp; (CPE)&nbsp; zapreminski modifikovane&nbsp; sa&nbsp; 5%&nbsp; (m:m)&nbsp; MnO2 je,&nbsp; pri&nbsp; optimizovanim&nbsp; uslovima&nbsp; i&nbsp; pri&nbsp; radnom&nbsp; potencijalu&nbsp; od 0,40 V&nbsp; u&nbsp; odnosu&nbsp; na&nbsp; zasićenu&nbsp; kalomelovu&nbsp; elektrodu&nbsp; (ZKE)&nbsp; u&nbsp; fosfatnom&nbsp; puferu&nbsp; pH&nbsp; 7,50&nbsp; kao pomoćnom elektrolitu, omogućila kvantifikaciju H <sub>2</sub>O<sub>2</sub> u opsegu koncentracija od 1,4 do 65 &micro;g mL -1 sa&nbsp; relativnom&nbsp; standardnom&nbsp; devijacijom&nbsp; (RSD)&nbsp; manjom&nbsp; od&nbsp; 10%.&nbsp; Ova&nbsp; metoda&nbsp; je&nbsp; primenjena&nbsp; za određivanje sadržaja H <sub>2</sub>O<sub>2 </sub>u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija)&nbsp; tretirane&nbsp; Fentonovim&nbsp; (Fe<sup> 2+</sup> i&nbsp; H <sub>2</sub>O<sub>2</sub> )&nbsp; i&nbsp; Fentonu-sličnim&nbsp; (Fe <sup>3+</sup> i&nbsp; H <sub>2</sub>O<sub>2</sub> )&nbsp; reagensima&nbsp; u&nbsp; cilju uklanjanja&nbsp; prirodnih&nbsp; organskih&nbsp; materija&nbsp; (POM)&nbsp; pri&nbsp; čemu&nbsp; su&nbsp; kori&scaron;ćene&nbsp; različite&nbsp; početne koncentracije&nbsp; gvožđa&nbsp; i&nbsp; različiti&nbsp; odnosi&nbsp; molarnih&nbsp; koncentracija&nbsp; gvožđa&nbsp; i&nbsp; H <sub>2</sub>O<sub>2</sub> .&nbsp; Utvrđeno&nbsp; je&nbsp; da oksidaciono&nbsp; stanje&nbsp; gvožđe&nbsp; (Fe<sup> 2+</sup> ili&nbsp; Fe <sup>3+</sup>)&nbsp; i&nbsp; molarni&nbsp; odnos&nbsp; jona&nbsp; Fe&nbsp; i&nbsp; H<sub> 2</sub>O<sub>2</sub> utiču&nbsp; na&nbsp; stepen potro&scaron;nje/razgradnje&nbsp; H<sub> 2</sub>O<sub>2</sub><br />u&nbsp; podzemnoj&nbsp; vodi&nbsp; sa&nbsp; visokim&nbsp; sadržajem&nbsp; POM.&nbsp; Takođe,&nbsp; u&nbsp; slučaju Fentonu-sličnog&nbsp; procesa,&nbsp; za&nbsp; sve&nbsp; početne&nbsp; koncentracije&nbsp; Fe <sup>3+</sup> i&nbsp; H <sub>2</sub>O<sub>2 ,</sub>&nbsp; signifikantna&nbsp; količina&nbsp; H <sub>2</sub>O<sub>2 </sub>ostaje&nbsp; neiskori&scaron;ćena,&nbsp; &scaron;to&nbsp; ukazuje&nbsp; na&nbsp; nižu&nbsp; efikasnost&nbsp; ovakvog&nbsp; sistema u&nbsp; poređenju&nbsp; sa&nbsp; Fentonovim procesom.&Scaron;tampana&nbsp; ugljenična&nbsp; elektroda&nbsp; (SPCE)&nbsp; zapreminski&nbsp; modifikovana&nbsp; sa&nbsp; MnO 2 kao medijatorom&nbsp; je&nbsp; primenjena&nbsp; za&nbsp; određivanje&nbsp; sadržaja&nbsp; H<sub> 2</sub>O<sub>2</sub> u&nbsp; toku&nbsp; Fentonovog&nbsp; (Fe <sup>2+</sup> ,&nbsp; H<sub>2</sub>O<sub>2</sub> )&nbsp; i vidljivom&nbsp; svetlo&scaron;ću&nbsp; potpomognutog&nbsp; foto-Fentonovog&nbsp; (Fe<sup> 2+ </sup>,&nbsp; H <sub>2</sub>O<sub>2 </sub>,&nbsp; h&nu;)&nbsp; procesa&nbsp; uklanjanja neonikotinoidnog&nbsp; insekticida&nbsp; acetamiprida&nbsp; (ACT).&nbsp; Pri&nbsp; optimizovanim&nbsp; uslovima&nbsp; (radni&nbsp; potencijal 0,40&nbsp; V&nbsp; u&nbsp; odnosu&nbsp; na&nbsp; ZKE,&nbsp; fosfatni&nbsp; pufer&nbsp; pH&nbsp; 7,50&nbsp; kao&nbsp; pomoćni&nbsp; elektrolit)&nbsp; amperometrijskog određivanja&nbsp; H <sub>2</sub>O<sub>2</sub> ,&nbsp; postignuta&nbsp; je&nbsp; linearnost&nbsp; u&nbsp; opsegu&nbsp; koncentracija&nbsp; 0,01&ndash;1,24&nbsp; mmol&nbsp; L-1(0,34&ndash; 42,2 &micro;g mL -1<br />) i vrednost RSD nije prelazila 4,2%. U ispitivanimuzorcima (nakon odgovarajućeg<br />pode&scaron;avanja pH vrednosti od 2,8 do 7,5 odmah nakon&nbsp; uzorkovanja radi stopiranja ili maksimalnog usporavanja&nbsp; procesa&nbsp; oksidacije,&nbsp; filtriranja,&nbsp; zamrzavanja&nbsp; i&nbsp; odmrzavanja&nbsp; neposredno&nbsp; pre&nbsp; merenja) sadržaj&nbsp; H <sub>2</sub>O<sub>2</sub> je&nbsp; određen&nbsp; metodom&nbsp; standardnog&nbsp; dodatka&nbsp; analiziranjem&nbsp; odgovarajućih amperometrijskih&nbsp; krivi.&nbsp; Paralelna&nbsp; HPLC-DAD&nbsp; merenja&nbsp; su&nbsp; vr&scaron;ena&nbsp; u&nbsp; cilju&nbsp; praćenja koncentracije/uklanjanja ACT. U slučaju foto-Fentonovog procesa (početne koncentracije 0,31; 2,0 i 3,0 mmol L -1 (70,0; 111,7 i 102,1 &micro;g mL -1 ) za ACT, Fe<br /><sup>2+</sup> i H <sub>2</sub>O<sub>2</sub>, redom) nakon 10 min H <sub>2</sub>O<sub>2 </sub>je izreagovao, a može se smatrati da je ACT uklonjen nakon 5 min. U toku Fentonovog procesa ACT je&nbsp; uklonjen&nbsp; nakon&nbsp; 20&nbsp; min&nbsp; tretmana&nbsp; i&nbsp; oko&nbsp; 10%&nbsp; početne&nbsp; koncentracije&nbsp; H <sub>2</sub>O<sub>2</sub> je&nbsp; ostalo&nbsp; u&nbsp; sistemu<br />neiskori&scaron;ćeno.CPE&nbsp; je&nbsp; povr&scaron;inski&nbsp; modifikovane&nbsp; kompozitom&nbsp; na&nbsp; bazi&nbsp; nanočestica&nbsp; Pt&nbsp; (&lt;&nbsp; 5&nbsp; nm)&nbsp; i grafitizovanog&nbsp; ugljenika&nbsp; (Pt-C,&nbsp; 10%&nbsp; Pt&nbsp; na&nbsp; Vulkanu&nbsp; XC72)&nbsp;&nbsp; etodom&nbsp; nano&scaron;enja&nbsp; kapi. Nemodifikovana&nbsp; CPE&nbsp; i&nbsp; modifikovana&nbsp; (Pt-C/CPE)&nbsp; su&nbsp;&nbsp; okarakterisane&nbsp; primenom&nbsp; SEM/EDS&nbsp; i&nbsp; CV merenja.&nbsp; Pt-C/CPE&nbsp; je&nbsp; pokazala&nbsp; izuzetne&nbsp; elektrokatalitičke&nbsp; osobine&nbsp; u&nbsp; pogledu&nbsp; elektrohemijskeredoks&nbsp; reakcije&nbsp; H<br /><sub>2</sub>O<sub>2</sub> u&nbsp; poređenju&nbsp; sa&nbsp; nemodifikovanom&nbsp; CPE&nbsp; u&nbsp; fosfatnom&nbsp; puferu&nbsp; (0,1 mol&nbsp; L -1 ;<br />pH 7,50),&nbsp; a&nbsp; takođe&nbsp; i&nbsp; u&nbsp; acetatnom&nbsp; puferu&nbsp; (0,1&nbsp; mol&nbsp; L -1 ;&nbsp; pH&nbsp; 4,50)&nbsp; kao&nbsp;&nbsp; pomoćnim&nbsp; elektrolitima. Prilikom&nbsp; amperometrijskog&nbsp; određivanja&nbsp; H <sub>2</sub>O<sub>2</sub> primenom&nbsp; Pt-C/CPE&nbsp; u&nbsp; model&nbsp; sistemima, zadovoljavajuća linearnost je postignuta u koncentracionom opseguH<sub>2</sub>O<sub>2</sub>od 0,15 do 1,45 &micro;g mL -1 ,dok su vrednosti GO iznosile 0,06 &micro;g mL -1 (pH 7,50, radni potencijal 0,20 V) i 0,10 &micro;g mL -1 (pH<br />4,50,&nbsp; radni&nbsp; potencijal&nbsp; 0,50&nbsp; V).&nbsp; Optimizovane&nbsp; analitičke&nbsp; metode&nbsp; su&nbsp; primenjene&nbsp; za&nbsp; određivanje sadržaja H <sub>2</sub>O<sub>2</sub> u komercijalno dostupnim proizvodima za ličnu negu: rastvoru za dezinfekciju (pH 7,50)&nbsp; i&nbsp; rastvoru&nbsp; za&nbsp; či&scaron;ćenje&nbsp; kontaktnih&nbsp; sočiva&nbsp; (pH&nbsp; 4,50).&nbsp; Amperometrijski&nbsp; dobijeni&nbsp; rezultati&nbsp; su&nbsp; u dobrom&nbsp; slaganju&nbsp; sa&nbsp; rezultatima&nbsp; dobijenim&nbsp; primenom&nbsp; tradicionalne&nbsp; spektrofotometrijske&nbsp; metode bazirane&nbsp; na&nbsp; titanijum-sulfatu&nbsp; kao&nbsp; reagensu&nbsp; sa&nbsp; određenim&nbsp; koncentracijama&nbsp; 2,91%&nbsp; i&nbsp; 2,94%&nbsp; za<br />dezinfekcioni rastvor i 3,04% i 3,17% za rastvor zakontaktna sočiva, redom. RSD je bila manja od 2%.&nbsp; Postignuti&nbsp; rezultati&nbsp; su&nbsp; u&nbsp; dobrom&nbsp; slaganju&nbsp; sa&nbsp; sadržajem&nbsp; H<br /><sub>2</sub>O<sub>2 </sub>deklarisanim&nbsp; od&nbsp; strane proizvođača (3%) u oba ispitivana uzorka. Pt-C/CPE je takođe testirana za praćenje koncentracije H<sub>2</sub>O<sub>2</sub> u rastvoru za kontaktna sočiva u toku procesa njegove neutralizacije/razgradnje. Nakon 6 h procesa neutralizacije, 24,68&nbsp; &micro;g mL -1 je bila određena koncentracija H <sub>2</sub>O<sub>2 ,</sub> &scaron;to je ispod dozvoljene<br />H<sub>2</sub>O<sub>2 </sub>koncentracije u rastvoru za kontaktna sočiva imajući u vidu granicu koja izaziva iritaciju oka. CPE&nbsp; je&nbsp; povr&scaron;inski&nbsp; modifikovana&nbsp; vi&scaron;ezidnim&nbsp; ugljeničnim&nbsp; nanocevima&nbsp; (MWCNT)&nbsp; i kompozitima MnO 2 -MWCNT ili Pt-MWCNT metodom nano&scaron;enja kapi radi pripreme jednostavnih, osetljivih i pouzdanih voltametrijskih senzora za&nbsp; određivanje H <sub>2</sub>O<sub>2 </sub>u odabranom uzorku. Rezultati SEM/EDS&nbsp; analize&nbsp; kompozitnih&nbsp; materijala&nbsp; su&nbsp; potvrdili da&nbsp; su&nbsp; medijatori,&nbsp; čestice&nbsp; MnO 2 i&nbsp; Pt, nasumično&nbsp; raspoređeni na povr&scaron;ini MWCNT i zastupljeni sa blizu 5% (m:m) u kompozitu izraženo<br />preko Mn i Pt. CV merenja su vr&scaron;ena sa pripremljenim radnim elektrodama u acetatnom (pH 4,50), fosfatnom&nbsp; (pH&nbsp; 7,50)&nbsp; i&nbsp; boratnom&nbsp; (pH&nbsp; 9,18)&nbsp; puferu&nbsp; kako&nbsp; bi&nbsp; se&nbsp; okarakterisalo&nbsp; osnovno elektrohemijsko&nbsp; pona&scaron;anje&nbsp; H <sub>2</sub>O<sub>2 </sub>i&nbsp; odabrali&nbsp; pogodni&nbsp; radni&nbsp; potencijali&nbsp; za&nbsp; amperometrijsko određivanje ovog ciljnog analita. Pt- WCNT/CPE je primenljiva za rad kako u fosfatnom puferu pH&nbsp; 7,50&nbsp; tako&nbsp; i&nbsp; u&nbsp; acetatnom&nbsp; puferu&nbsp; pH&nbsp; 4,50&nbsp; V&nbsp; kako&nbsp; pri&nbsp; negativnim&nbsp; tako&nbsp; i&nbsp; pri&nbsp; pozitivnim&nbsp; radnim<br />potencijalima, pri&nbsp; čemu su vrednosti RSD uglavnom ispod 2,5%. U slučaju MnO 2<br />-MWCNT/CPE, na&nbsp; potencijalu&nbsp; 0,30&nbsp; V&nbsp; i&nbsp; vi&scaron;im&nbsp; vrednostima,&nbsp; oksidacioni&nbsp; signali&nbsp; H<br /><sub>2</sub>O<sub>2</sub> su&nbsp; signifikantni&nbsp; u&nbsp; blago alkalnoj sredini (pH 7,50), pri pH 4,50 ova elektroda pokazuje nezadovoljavajuće pona&scaron;anje, dok&nbsp; pri pH 9,18 ima prihvatljive performanse. Granice određivanja (GO) su bile u oblasti &micro;g mL -1 . H <sub>2</sub>O<sub>2</sub> je&nbsp; određen&nbsp; u&nbsp; spajkovanom&nbsp; uzorku&nbsp; mleka&nbsp; metodom&nbsp; standardnog&nbsp; dodatka&nbsp; nakon&nbsp; odgovarajuće pripreme&nbsp; uzorka&nbsp; (pH&nbsp; pode&scaron;avanje&nbsp; i&nbsp; centrifugiranje)&nbsp; i&nbsp; primenom&nbsp; optimizovane&nbsp; amperometrijske procedure (acetatni pufer pH 4,50, radni&nbsp; potencijal-0,75 V) koristeći Pt-MWCNT/CPE kao radnu elektrodu. RSD za tri&nbsp; ponovljena merenja je iznosila 2,5%, dok je prinos metode bio ne&scaron;to veći od 71%.<br />Kompozitni materijali koji se sastoje od MWCNT i&nbsp; čestica na bazi Pd (Pd-MWCNT) ili Pt (Pt-MWCNT) su primenjeni za pripremu zapreminski modifikovanih SPCE (Pd-MWCNT-SPCE i Pt-MWCNT-SPCE)&nbsp; i&nbsp; povr&scaron;inski&nbsp; modifikovane&nbsp; SPCE&nbsp; (Pd-MWCNT/SPCE).&nbsp; Ove&nbsp; elektrode,&nbsp; kao&nbsp; i nemodifikovana&nbsp; SPCE&nbsp; i&nbsp; MWCNT-SPCE,&nbsp; su&nbsp; okarakterisane primenom&nbsp; CV&nbsp; i&nbsp; amperometrije&nbsp; u fosfatnom puferu pH 7,50 radi određivanja H <sub>2</sub>O<sub>2</sub> . Pd-MWCNT-SPCE i Pd-MWCNT/SPCE su se pokazale&nbsp; pogodnim&nbsp; za&nbsp; određivanje&nbsp; H <sub>2</sub>O<sub>2</sub> na&nbsp; radnim&nbsp; potencijalima&nbsp; između&nbsp; -0,50&nbsp; i&nbsp; 0,50&nbsp; V,&nbsp; a&nbsp; PtMWCNT-SPCE na ispitivanim radnim potencijalima od -0,80 do 0,70 V. Ove&nbsp; elektrode su zatim modifikovane&nbsp; enzimom&nbsp; glukoza&nbsp; oksidazom&nbsp; (GOx)&nbsp; metodom&nbsp; nano&scaron;enja&nbsp; kapi&nbsp; rastvora&nbsp; GOx&nbsp; i Nafion &reg; -a&nbsp; na&nbsp; njihovu&nbsp; povr&scaron;inu,&nbsp; pri&nbsp; čemu&nbsp; je&nbsp; optimizovana&nbsp; količina&nbsp; nanetog&nbsp; biofilma.&nbsp; GOx/PdMWCNT-SPCE&nbsp; je&nbsp; pokazala&nbsp; bolje&nbsp; analitičke&nbsp; performanse&nbsp; za&nbsp; određivanje&nbsp; glukoze&nbsp; u&nbsp; poređenju&nbsp; sa GOx/Pd- WCNT/SPCE.&nbsp; Kao&nbsp; optimalan&nbsp; radni&nbsp; potencijal&nbsp; GOx/Pd-MWCNT-SPCE&nbsp; je&nbsp; odabrana<br />vrednost&nbsp; potencijala&nbsp; -0,40&nbsp; V&nbsp; u&nbsp; odnosu&nbsp; na&nbsp; ZKE,&nbsp; sa&nbsp; zadovoljavajućom&nbsp; linearno&scaron;ću&nbsp; u&nbsp; ispitivanom opsegu&nbsp; koncentracija&nbsp; glukoze&nbsp; od&nbsp; 0,16&nbsp; do&nbsp; 0,97&nbsp; mmol&nbsp; L -1 (od&nbsp; 29,1&nbsp; do&nbsp; 174&nbsp; &micro;g&nbsp; mL -1),&nbsp; dok&nbsp; je&nbsp; GO iznosila 0,14 mmol L -1 (25 &micro;g mL<br />-1 ). Optimizovana metoda zasnovana na GOx/Pd-MWCNT-SPCE je&nbsp; uspe&scaron;no&nbsp; primenjena&nbsp; za&nbsp; određivanje&nbsp; glukoze&nbsp; u&nbsp; uzorku&nbsp; livadskog&nbsp; meda.&nbsp; Dobijeni&nbsp; rezultati&nbsp; su&nbsp; u dobroj&nbsp; saglasnosti&nbsp; sa&nbsp; onima&nbsp; dobijenim&nbsp; primenom&nbsp; komercijalno&nbsp; dostupnog&nbsp; aparata&nbsp; za&nbsp; merenje glukoze. Pogodan radni potencijal za GOx/Pt-MWCNT-SPCE je bio -0,50 V u odnosu na ZKE, pri čemu je zadovoljavajuća linearnost postignuta u ispitivanom opsegu koncentracija glukoze od 65,8 do 260,6 &micro;g mL -1 , sa GO 35 &micro;g mL -1 . Optimizovana metoda zasnovana na GOx/Pt-MWCNT-SPCE je&nbsp; uspe&scaron;no&nbsp; primenjena&nbsp; za&nbsp; određivanje&nbsp; glukoze&nbsp; u&nbsp; u&nbsp; uzorku&nbsp; belog&nbsp; grožđa&nbsp; i&nbsp; uzorku&nbsp; tableta (Traubenzucker-bonbons),&nbsp; pri&nbsp; čemu&nbsp; su&nbsp; dobijeni&nbsp; rezultati&nbsp; u&nbsp; dobroj&nbsp; saglasnosti&nbsp; sa&nbsp; rezultatima dobijenim primenom Accu-Chek aparata.<br />Na&nbsp; osnovu&nbsp; dobijenih&nbsp; rezultata&nbsp; može&nbsp; se&nbsp; zaključiti&nbsp; da&nbsp; su&nbsp; razvijene&nbsp; analitičke&nbsp; metode&nbsp; pre svega jednostavne, pouzdane i pogodne za dobijanje brzih informacija o sadržaju H <sub>2</sub>O<sub>2</sub> u različitim tipovima&nbsp; uzoraka.&nbsp; Svakako&nbsp; odabir&nbsp; pogodne&nbsp; radne&nbsp; elektrode,&nbsp; kao&nbsp; i&nbsp; optimizacija&nbsp; eksperimentalnih uslova su ključni faktori za uspe&scaron;no određivanje H <sub>2</sub>O<sub>2</sub></p> / null / <p>The aim of this doctoral dissertation was the development of fast and reliable voltammetric methods&nbsp; based&nbsp; on&nbsp; the&nbsp; application&nbsp; of&nbsp; simple&nbsp; and&nbsp; contemporary&nbsp; electrodes/sensors&nbsp; based&nbsp; on carbonaceous materials (carbon paste made of graphite powder and paraffin oil and screen printed carbon electrodes) for the determination of H <span id="cke_bm_571S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_571E" style="display: none;">&nbsp;</span>O<sub>2</sub> in the selected complex model and real samples.For this purpose, applicability of different working electrodes was investigated.The&nbsp; amperometric&nbsp; method&nbsp; based&nbsp; on&nbsp; carbon&nbsp; paste&nbsp; electrode&nbsp; (CPE)&nbsp; bulk- modified&nbsp; &nbsp;&nbsp; with 5% (m:m) MnO 2 , under optimized conditions, with a working potential of 0.40 V vs. the saturated calomel&nbsp; elect<span id="cke_bm_572E" style="display: none;">&nbsp;</span>rode&nbsp; (SCE)&nbsp; and&nbsp; a&nbsp; phosphate&nbsp; buffer&nbsp; solution&nbsp; (pH&nbsp; 7.50)&nbsp; as&nbsp; supporting&nbsp; electrolyte, enabled the quantitation of H <span id="cke_bm_577S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_577E" style="display: none;">&nbsp;</span>O<sub>2</sub>in the concentration interval from 1.4 to 65 &micro;g mL &minus;1 with a relative standard deviation (RSD) of less than 10%. This meth<span id="cke_bm_578E" style="display: none;">&nbsp;</span>od was applied for the determination of the H<span id="cke_bm_583S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_583E" style="display: none;">&nbsp;</span>O<sub>2 </sub>consumption&nbsp; in&nbsp; samples&nbsp; of&nbsp; groundwater&nbsp; fro<span id="cke_bm_584E" style="display: none;">&nbsp;</span>m&nbsp; the&nbsp; Central&nbsp; Banat&nbsp; region&nbsp; (Province&nbsp; of Vojvodina, Serbia) treated by the Fenton (Fe <sup>2+ </sup>and H <sub>2</sub>O<sub>2</sub> ) and Fenton-&nbsp; like (Fe <sup>3+</sup>and H <sub>2</sub>O<sub>2</sub> ) reagents to remove natural organic matter (NOM) at&nbsp; differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H<sub>2</sub>O<sub>2</sub> . It was found that the form of Fe (Fe <sup>2+</sup> or Fe <sup>3+</sup> )and the molar&nbsp; ratio to H <sub>2</sub>O<sub>2</sub>influenced the degree of the H<sub> 2</sub>O<sub>2</sub> decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe <sup>3+</sup> and H<span id="cke_bm_604S" style="display: none;">&nbsp;</span><sub> 2</sub><span id="cke_bm_604E" style="display: none;">&nbsp;</span>O<sub>2</sub>, a sign<span id="cke_bm_605E" style="display: none;">&nbsp;</span>ificant amount of H<span id="cke_bm_610S" style="display: none;">&nbsp;</span><sub> 2</sub><span id="cke_bm_610E" style="display: none;">&nbsp;</span>O<sub>2</sub> remained unused, whi<span id="cke_bm_611E" style="display: none;">&nbsp;</span>ch also indicates a lower efficiency of such system compared to the Fenton process. Screen&nbsp; printed&nbsp; carbon&nbsp; electrode&nbsp; (SPCE)&nbsp; bulk-modified&nbsp; with&nbsp; MnO&nbsp;<sub> 2</sub> as&nbsp; a&nbsp; mediator&nbsp; was applied&nbsp; for&nbsp; amperometric&nbsp; determination&nbsp; of&nbsp; the&nbsp; H <span id="cke_bm_617S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_617E" style="display: none;">&nbsp;</span>O<sub>2</sub> content&nbsp; during&nbsp; the&nbsp; Fenton&nbsp; (Fe <sup>2+</sup> ,&nbsp; H <span id="cke_bm_624S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_624E" style="display: none;">&nbsp;</span>O<sub>2 </sub>)&nbsp; and <span id="cke_bm_625E" style="display: none;">&nbsp;</span>visible&nbsp; light-assisted<span id="cke_bm_618E" style="display: none;">&nbsp;</span>,&nbsp; photo-Fenton&nbsp; (Fe <sup>2+&nbsp;</sup> ,&nbsp; H <span id="cke_bm_631S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_631E" style="display: none;">&nbsp;</span>O<sub>2</sub> ,&nbsp; h&nu;)<span id="cke_bm_632E" style="display: none;">&nbsp;</span>&nbsp; based&nbsp; removal&nbsp; of&nbsp; neonicotinoid&nbsp; insecticide acetamiprid (ACT). Under&nbsp; optimized conditions (working potential of 0.40 V vs. SCE, phosphate buffer&nbsp; pH&nbsp; 7.50&nbsp; as&nbsp; supporting&nbsp; electrolyte)&nbsp; amperometric&nbsp; determination&nbsp; of&nbsp; H <span id="cke_bm_637S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_637E" style="display: none;">&nbsp;</span>O<sub>2 </sub>showed&nbsp; a&nbsp; linear dynamic range from 0.01 to 1.24 mmol L -1 (from 0.34 to 42.2 &micro;g mL -1) and the RSD did not exceed 4.2%. In the investigated samples (after appropriate pH adjustment from 2.8 to 7.5 instantly after the sampling<span id="cke_bm_638E" style="display: none;">&nbsp;</span> to stop or maximum decelerate the oxidation processes, filtering, and storage of the deep- frozen sample with defrosting immediately before the measurements) the H <span id="cke_bm_643S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_643E" style="display: none;">&nbsp;</span>O<sub>2</sub>&nbsp; contents were determined by the standard addition method by analyzing the corresponding amperometric curves. Parallel HPLC-DAD measurements were performed to monito<span id="cke_bm_644E" style="display: none;">&nbsp;</span>r the concentration/removal of ACT. In the case of the photo- Fenton process (initial concentrations: 0.31; 2.0 and 3.0 mmol L -1 (70.0; 111.7 and 102.1 &micro;g mL -1 ) of ACT, Fe<sup> 2+</sup> and H <span id="cke_bm_650S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_650E" style="display: none;">&nbsp;</span>O<sub>2</sub>, respec<span id="cke_bm_651E" style="display: none;">&nbsp;</span>tively) after 10 min of irradiation H <span id="cke_bm_656S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_656E" style="display: none;">&nbsp;</span>O<sub>2</sub> was&nbsp; consumed&nbsp; and&nbsp; it&nbsp; can&nbsp; be&nbsp; consi<span id="cke_bm_657E" style="display: none;">&nbsp;</span>dered&nbsp; that&nbsp; ACT&nbsp; was&nbsp; removed&nbsp; after&nbsp; 5&nbsp; min.&nbsp; During&nbsp; the&nbsp; Fenton process ACT was removed after 20 min of treatment and around 10% of the initial concentration of the H 2O2 remained still unused.<br />CPE&nbsp; was&nbsp; surface&nbsp; modified&nbsp; with&nbsp; a&nbsp; composite&nbsp; of&nbsp; Pt&nbsp; nanoparticles&nbsp; (&lt;&nbsp; 5&nbsp; nm)&nbsp; on&nbsp; graphitized carbon (Pt-C, 10% Pt on Vulcan XC72) by simply dropcoating method. The unmodified CPE and the&nbsp; modified&nbsp; one&nbsp; (Pt-C/CPE)&nbsp; were&nbsp; characterized&nbsp; by&nbsp;&nbsp; EM/EDS&nbsp; and&nbsp; CV&nbsp; measurements.&nbsp; The&nbsp; PtC/CPE showed remarkable electrocatalytic propertiestoward the electrochemical redox reaction of H<span id="cke_bm_662S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_662E" style="display: none;">&nbsp;</span>O<sub>2</sub> compared to&nbsp; modified CPE in phosphate buffer (0.1 mol L -1 ; pH 7.50), as well in acetatebuffer&nbsp; (0.1 mol&nbsp; L -1 ; pH .50) supporting&nbsp; electrolytes. Amperometry of&nbsp; H2O2 in the concentration range from 0.15 to 1.45 &micro;g mL -1 with the Pt-C/CPE showed acceptable linearity, while the obtained values of LOQs were 0.06 &micro;g mL -1&nbsp; (pH 7.50, working potential 0.20 V) and 0.10 &micro;g mL -1 (pH 4<span id="cke_bm_663E" style="display: none;">&nbsp;</span>.50, working potential 0.50 V). The proposed analytical&nbsp; methods were applied to the determination of the H 2O2 content in commercially available personal care products; i.e., disinfection (pH 7.50) and contact lens cleaning solutions (pH 4.50). The obtained amperometric results are in good agreement with those measured by traditional titanium sulfatereagent based spectrophotometric method with determined concentrations as 2.91% and 2.94%&nbsp; for the disinfection product, and 3.04% and 3.17% for the contact lens solution, respectively. RSD was lower than 2%. The obtained results are in a good agreement with the amounts of the H<span id="cke_bm_668S" style="display: none;">&nbsp;</span><sub> 2</sub><span id="cke_bm_668E" style="display: none;">&nbsp;</span>O<sub>2 </sub>declared by producers (3%) in the both investigated samples. The Pt-C/CPE was also tested for monitoring of the H<span id="cke_bm_674S" style="display: none;">&nbsp;</span><sub> 2</sub><span id="cke_bm_674E" style="display: none;">&nbsp;</span>O<sub>2</sub> residual concentration in contact lens&nbsp; solution&nbsp; during&nbsp; its&nbsp; neutralization/decomposition&nbsp; rocess.&nbsp; At&nbsp; 6&nbsp; h&nbsp; of<span id="cke_bm_675E" style="display: none;">&nbsp;</span>&nbsp; neutralization&nbsp; treatment 24.68 &micro;g mL -1 of the H <span id="cke_bm_680S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_680E" style="display: none;">&nbsp;</span>O<sub>2 </sub>was&nbsp; determined which is almost half of the allowedH2<span id="cke_bm_681E" style="display: none;">&nbsp;</span>O2 concentration in the case of the contact lens solution concerningthe limit of eye irritation. CPE&nbsp; was&nbsp; surface&nbsp;&nbsp; modified&nbsp; with&nbsp; multiwalled&nbsp; carbon&nbsp; nanotubes&nbsp; (MWCNT)&nbsp; and&nbsp; with composites of MnO<sub> 2 </sub>-MWCNT or Pt-MWCNT by drop coating method to prepare simply, sensitive and reliable volta<span id="cke_bm_669E" style="display: none;">&nbsp;</span>mmetric sensors for the determination of H <span id="cke_bm_687S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_687E" style="display: none;">&nbsp;</span>O<sub>2 </sub>in selected sample. The results of the&nbsp; SEM/<span id="cke_bm_688E" style="display: none;">&nbsp;</span>EDS&nbsp; analysis&nbsp; of&nbsp; composite&nbsp; materials&nbsp; have&nbsp; confirmed&nbsp; that&nbsp; the&nbsp; mediators,&nbsp; MnO <sub>2</sub> and&nbsp; Pt&nbsp; articles, are randomly distributed on the surface of MWCNT and represent nearly 5% (m:m) of the composite expressed as Mn and Pt. CV measurements were performed&nbsp; with prepared electrodes in acetate&nbsp; (pH&nbsp; 4.50),&nbsp; phosphate&nbsp; (pH&nbsp; 7.50)&nbsp; and&nbsp; borate&nbsp; (pH&nbsp; 9.18)&nbsp; buffers&nbsp; to&nbsp; characterize&nbsp; the&nbsp; basic electrochemical&nbsp; behavior&nbsp; of&nbsp; H <span id="cke_bm_694S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_694E" style="display: none;">&nbsp;</span>O<sub>2</sub> and&nbsp; to&nbsp; select&nbsp; the&nbsp; working&nbsp; potentials&nbsp; suitable&nbsp; for&nbsp; amperometric determination&nbsp; of&nbsp; this&nbsp; target&nbsp; analyte.&nbsp; The&nbsp; Pt-MWCNT/CPE&nbsp; performs&nbsp; well&nbsp; in&nbsp; phosphate&nbsp; buffer pH .50 and acetate buffer solution pH 4.50 in the&nbsp; negative as well as in the positive polarization range with RSD mainly lower than 2.5%. In case of MnO<sub> 2 </sub>-MWCNT/CPE at <span id="cke_bm_695E" style="display: none;">&nbsp;</span>0.30 V and above the H<span id="cke_bm_701S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_701E" style="display: none;">&nbsp;</span>O<sub>2 </sub>oxidation signal is rem<span id="cke_bm_702E" style="display: none;">&nbsp;</span>arkable in slightly alkaline media (pH 7.50), at pH 4.50 this electrode showed poor behavior and at pH 9.18 offered acceptable performance. LOQs were in the &micro;g mL -1 concentration&nbsp; range.&nbsp; H<span id="cke_bm_707S" style="display: none;">&nbsp;</span><sub>2</sub><span id="cke_bm_707E" style="display: none;">&nbsp;</span>O<sub>2 </sub>was&nbsp; determined&nbsp; in&nbsp; a&nbsp; spiked&nbsp; milk&nbsp; sample&nbsp; by&nbsp; standard addition&nbsp; method after&nbsp; appropriate&nbsp; sample&nbsp; preparation&nbsp; (pH&nbsp; adjustment and&nbsp; centrifugation)&nbsp; and&nbsp; using&nbsp; optimized amperometric p<span id="cke_bm_708E" style="display: none;">&nbsp;</span>rocedure (acetate buffer pH 4.50, working potential -0.75 V) by Pt-MWCNT/CPE as a working electrode. RSD for three repeated measurements was 2.5%, while the recovery of the method was a bit higher than 71%. The&nbsp; composite&nbsp; materials&nbsp; consisting&nbsp; of&nbsp; MWCNT&nbsp; and&nbsp; Pd&nbsp; (Pd-MWCNT)&nbsp; or&nbsp; Pt&nbsp; containing particles&nbsp; (Pt-WCNT)&nbsp; were&nbsp; applied&nbsp; to&nbsp; the&nbsp; preparation&nbsp; of&nbsp; bulk- modified&nbsp; SPCEs&nbsp; (Pd-MWCNTSPCE and Pt-MWCNT-SPCE) and surface modifiedSPCE (Pd- MWCNT/SPCE). These electrodes, as well as unmodified SPCE and MWCNT-SPCE,&nbsp; were characterized by CV and&nbsp; amperometry&nbsp; in phosphate&nbsp; buffer&nbsp; solution&nbsp; of&nbsp; pH&nbsp; 7.50&nbsp; for&nbsp; the&nbsp; H<span id="cke_bm_713S" style="display: none;">&nbsp;</span><sub> 2</sub><span id="cke_bm_713E" style="display: none;">&nbsp;</span>O<sub>2 </sub>determination.&nbsp; Pd-MWCNT-SPCE&nbsp; and&nbsp; PdMWCNT/SPCEare convenient for the etermination of H 2O2 at working potentials from -0.50 to 0.50 V, and Pt-MWCNT-SPCE at investigated working potentials in the range from -0.80 to 0.70 V. These electrodes were then modified with glucose&nbsp; oxidase (GOx) by drop coating a solution of GOxand Nafion &reg; on their surface, whereby the applied amount of biococktail was optimized. GOx/PdMWCNT-SPCE&nbsp; showed&nbsp; better&nbsp; analytical&nbsp; performance&nbsp; for&nbsp; glucose&nbsp; determination&nbsp; in&nbsp; comparison with&nbsp; GOx/Pd-MWCNT/SPCE.&nbsp; The&nbsp; optimal&nbsp; working&nbsp; potential&nbsp; for&nbsp; GOx/Pd-MWCNT- SPCE&nbsp; was -0.40 V vs. SCE and <span id="cke_bm_714E" style="display: none;">&nbsp;</span>satisfactory linearity was obtained in the investigated glucose concentration range from 0.16 to 0.97 mmol L -1 (from 29.1 to 174&nbsp; &micro;g mL -1 ), hile the LOQ was 0.14 mmol L -1 (25 &micro;g mL -1 ). The optimized method based on GOx/Pd-MWCNT-SPCE was successfully applied to the determination of glucose in multifloral honey sample.&nbsp; The results are in a good agreement with those&nbsp; obtained by commercially available equipment for determination of glucose. Optimal working potential&nbsp; for&nbsp; GOx/Pt-MWCNT-SPCE&nbsp; was&nbsp; -0.50&nbsp; V&nbsp; vs.&nbsp; SCE,&nbsp; and&nbsp; the&nbsp;&nbsp; satisfactory&nbsp; linearity&nbsp; was obtained in the investigated concentration range ofglucose from 65.8 to 260.6&nbsp; &micro;g mL -1 , with LOQ of 35&nbsp; &micro;g mL -1 . The optimized method based on GOx/Pt- MWCNT-SPCE was successfully applied for determination of glucose in white grape and glucose tablets (Traubenzucker-bonbons) samples, whereby&nbsp; the&nbsp; obtained&nbsp; results&nbsp; were&nbsp; in&nbsp; a&nbsp; good&nbsp; agreement&nbsp; with&nbsp; the&nbsp; results&nbsp; obtained&nbsp; by&nbsp; Accu-Chek device. Based on the results, the developed analytical methods are first of all simple, reliable and suitable&nbsp; for&nbsp; obtaining&nbsp; fast&nbsp; information&nbsp; about&nbsp; the&nbsp; content&nbsp; of&nbsp; H <sub>2</sub>O<sub>2</sub> in&nbsp; different&nbsp; types&nbsp; of&nbsp; samples. Certainly the selection of a suitable working electrode, as well as the optimization of experimental conditions are key factors for the successful determination of H<sub>2</sub>O<sub>2 </sub>.</p>

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