Eutypa dieback, one of several grapevine trunk diseases (GTDs), is of serious concern to the grape industry globally. This disease is caused by the fungus Eutypa lata but it is often seen in consortia growth with Phaeoacremonium minimum and Phaeomoniella chlamydospora. It is vital to understand the mechanisms for how this disease functions to develop control measures to combat it. Brown rot fungi are able to use a complex of low molecular weight (LMW) metabolites to induce a Fenton reaction to deconstruct woody tissue. These metabolites are part of a chelator mediated Fenton (CMF) chemistry that produces reactive oxygen species that are capable of depolymerizing wood polymers. We propose that a mechanism similar to CMF chemistry may be occurring in grapevine trunk disease pathogens. This thesis investigates how LMW metabolites produced by the fungi contribute to the disease and decay progression in GTDs. Research on Mite control in the laboratory with abamectin was also investigated, as research in this area was required when mites infested our fungal cultures and suitable laboratory controls were not available. Research on the GTD fungi was initiated by first examining whether metabolites produced by the three fungi can function in a manner to promote reactions like the CMF system. We separated and identified specific metabolites that potentially could contribute to CMF chemistry. We found that all three GTD fungi were able to produced LMW metabolites that promoted CMF chemistry, and we hypothesized that this mechanism contributes to processes leading to tissue necrosis in grapevine trunk wood. To explore the development of effective control measures based on this newly discovered mechanism for pathogenesis, we also explored the use of antioxidant/chelator compounds, BHA and BHT, in the control of the consortia fungi. Biocontrol organisms, Bacillus subtilis and Trichoderma atroviride, that produce antioxidants were also tested as biocontrols against the fungi involved in Eutypa Dieback disease. We found that BHA was highly effective in inhibiting fungal growth for all three fungi at concentrations higher than 0.5mM, and both B. subtilis and T. atroviride proved to be effective biocontrol agents in inhibiting E. lata, P. minimum, and P. chlamydospora.

[EN] In this Doctoral Thesis the reactivity of a group of emerging pollutants (EP) present in the output waters of urban treatment plants and the implementation of a photo-Fenton process in slightly acidic pH conditions using bio-organic solubles (SBO) as auxiliary chemicals have been studied. First, a mechanistic study was performed to investigate the role played by various reactive species in the oxidation of a mixture of emerging pollutants generated photochemically through advanced oxidation processes. These oxidizing species are the hydroxyl radical (OH), singlet oxygen (1O2) and the excited states of photocatalysts able to act through electron transfer processes. Results show that the EP degradation from the photo-Fenton process is too complex to be explained exclusively by the direct reaction of radical OH¿. More likely, OH radical reacts with further species present in the medium, so that long-lived radicals are generated and contribute to the degradation of EP or participate in chain processes. Rose bengal, known 1O2 generator, showed very low reactivity with EP under photochemical conditions. This fact together with the low values obtained for the rate constants in the reaction of 1O2 with EP, indicate that degradation of EP with singlet oxygen at these concentrations is very inefficient. Electron transfer processes studied using triphenylpyrylium (TPP+) and triphenylthiopyrylium (TPTP+) showed that degradation of EP were produced through the excited singlet and triplet states of the photocatalysts, slightly higher results were obtained by using the TPTP+. SBO, isolated from the wet fraction of municipal waste, are formed by a mixture of macromolecules with a wide range of sizes that goes from 67 to 463 kgmol-1. Furthermore, chemical composition of SBO resembles that of natural organic matter that has been employed in solar photochemical processes for wastewater treatment. Characterization of SBO has shown that these substances are biocompatible, stable after 24 hours of irradiation and able to improve the efficiency of photo-Fenton under slightly acidic pH. The results obtained in the optimization of the operational variables of the photo-Fenton process in the presence of SBO suggest that the mechanism of this process has changed, so that the optimum pH value of 2,8 has shifted to values close to 4. Therefore, the hydroxyl radical is not the main specie but others species could play a role; however they have not been unequivocally identified due to the complexity process. Moreover, SBO are able to generate reactive species; however their efficiency depends on the balance between the generation of reactive species and the inner filter effect produced by the deep color of SBO and also by the competition for the generated reactive species between SBO and the pollutants / [ES] En la presente Tesis Doctoral se estudió la reactividad de un conjunto de contaminantes emergentes (CE) presentes en aguas naturales de salida de depuradoras urbanas y la posibilidad de implementar un proceso foto-Fenton en condiciones de pH ligeramente ácidas empleando sustancias solubles bio-orgánicas (SBO) como auxiliares químicos. En primer lugar se realizó un estudio mecanístico para indagar sobre el papel desarrollado por diversas especies reactivas, generadas fotoquímicamente mediante procesos de oxidación avanzada, en la oxidación de una mezcla de contaminantes emergentes. Entre estas especies oxidantes se encuentra el radical hidroxilo (OH.), el oxígeno singlete (1O2), y los estados excitados de los fotocatalizadores capaces de actuar en procesos de transferencia electrónica. Los resultados obtenidos muestran que el proceso de degradación de los CE mediante foto-Fenton es demasiado complejo para poder ser explicado únicamente mediante la reacción directa del radical OH. Posiblemente, tras ser generado, el radical OH reacciona con las especies presentes en el medio de forma que se generan radicales de vida larga que contribuyen a la degradación de los CE o bien inicia procesos en cadena. El rosa de bengala, conocido generador de 1O2, mostró muy baja reactividad con los CE en condiciones fotoquímicas. Este hecho unido a los bajos valores obtenidos para las constantes de reacción del 1O2 con los CE, nos indica que la degradación mediante reacción con oxígeno singlete a estas concentraciones es muy ineficiente. Los estudios de los procesos de transferencia electrónica empleando trifenilpirilio (TPP+) y trifeniltiopirilio (TPTP+) muestran que la degradación de los CE se produce desde los estados excitados singlete y triplete de los fotocatalizadores, obteniéndose unos resultados ligeramente superiores mediante el empleo del TPTP+. Los SBO son materiales extraídos de la fracción húmeda de los residuos urbanos. Estas sustancias están constituidas por una mezcla de macromoléculas con un amplio rango de tamaños que oscila de 67 a 463 kgmol-1. Además su composición química presenta similitudes estructurales con algunas sustancias que se encuentran en la materia orgánica natural y que han sido empleadas en procesos fotoquímicos solares para el tratamiento de aguas residuales. La caracterización de los SBO ha demostrado que estas sustancias son biocompatibles, estables tras 24 horas de irradiación y capaces de mejorar la eficiencia del foto-Fenton en condiciones de pH ligeramente ácidas. Los resultados obtenidos en la optimización de las variables operacionales en el proceso foto-Fenton en presencia de SBO sugieren que se ha producido una modificación en el mecanismo del proceso foto-Fenton de forma que se ha desplazado el valor óptimo de pH desde 2,8 a valores cercanos a 4. Por tanto el radical hidroxilo puede no ser la especie principal y entrar en juego otras especies que no han podido ser identificadas con certeza debido a la complejidad del proceso. Los SBO son capaces de generar especies reactivas, sin embargo se ha de llegar a un equilibrio entre la generación de especies reactivas y el efecto filtro producido por su acusada coloración, así como por la competencia de los propios SBO por las especies reactivas generadas. / [CA] En la present Tesi Doctoral es va estudiar la reactivitat d'un conjunt de contaminants emergents (CE) presents en aigües d'eixida de depuradores urbanes i la possibilitat d'implementar un procés foto-Fenton en condicions de pH lleugerament àcides emprant substàncies solubles bio-orgàniques (SBO) com auxiliars químics. En primer lloc es va realitzar un estudi mecanístic per indagar sobre el paper desenvolupat per diverses espècies reactives, generades fotoquímicament mitjançant processos d'oxidació avançada, en l'oxidació d'una mescla de contaminants emergents. Entre aquestes espècies oxidants es troba el radical hidroxil (OH), l'oxigen singlet (1O2), i els estats excitats dels fotocatalitzadors capaços de actuar per processos de transferència electrònica. Els resultats obtinguts mostren que el procés de degradació dels CE mitjançant foto-Fenton és massa complex per poder ser explicat únicament per la reacció directa del radical OH. Possiblement després de ser generat, el radical OH reacciona amb les espècies presents en el medi de manera que es generen radicals de vida llarga que contribueixen a la degradació dels CE o bé inicia processos en cadena. El rosa de bengala, conegut generador de 1O2, va mostrar molt baixa reactivitat amb els CE en condicions fotoquímiques. Aquest fet unit als baixos valors obtinguts per a les constants de reacció del 1O2 amb els CE, ens indica que la degradació mitjançant reacció amb oxigen singlet a aquestes concentracions és molt ineficient. Els estudis dels processos de transferència electrònica utilitzant trifenilpirili (TPP+) i trifeniltiopirili (TPTP+) mostren que la degradació dels CE es produeix per mitjà dels estats excitats singlet i triplet dels fotocatalitzadors, obtenint uns resultats lleugerament superiors mitjançant l'ús del TPTP+. Els SBO són materials obtinguts de la fracció humida dels residus urbans. Aquestes substàncies estan constituïdes per una barreja de macromolècules amb un ampli rang de pesos moleculars que van de 67 a 463 kgmol-1. A més la seva composició química presenta similituds estructurals amb algunes substàncies que es troben en la matèria orgànica natural i que han sigut utilitzades en processos fotoquímics solars per al tractament d'aigües residuals. La caracterització dels SBO ha demostrat que aquestes substàncies són biocompatibles, estables després de 24 hores d'irradiació i son capaços de millorar l'eficiència del foto-Fenton en condicions lleugerament àcides. Els resultats obtinguts en l'optimització de les variables operacionals en el procés foto-Fenton en presència de SBO semblen suggerir que s'ha produït una modificació en el mecanisme de manera que s'ha desplaçat el valor òptim de pH des 2,8 a valors propers a 4. Pertant el radical hidroxil deixa de ser l'espècie principal i entren en joc altres espècies que no han pogut ser identificades amb certesa a causa de la complexitat del procés. Els SBO són capaços de generar espècies reactives, però s'ha d'arribar a un equilibri entre la generació d'espècies reactives i l'efecte filtre produït per la seua acusada coloració, així com per la competència dels propis SBO per les espècies reactives generades. / Gomis Vicens, J. (2015). Efecto de distintas especies reactivas generadas fotoquímicamente sobre la eliminación de contaminantes presentes en aguas naturales [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/51667

<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 ₂O₂u&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 ₂O₂ 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 ₂O₂u uzorcima podzemne vode iz centralnog Banata (Pokrajina Vojvodina, Srbija)&nbsp; tretirane&nbsp; Fentonovim&nbsp; (Fe²⁺ i&nbsp; H ₂O₂ )&nbsp; i&nbsp; Fentonu-sličnim&nbsp; (Fe ³⁺ i&nbsp; H ₂O₂ )&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 ₂O₂ .&nbsp; Utvrđeno&nbsp; je&nbsp; da oksidaciono&nbsp; stanje&nbsp; gvožđe&nbsp; (Fe²⁺ ili&nbsp; Fe ³⁺)&nbsp; i&nbsp; molarni&nbsp; odnos&nbsp; jona&nbsp; Fe&nbsp; i&nbsp; H₂O₂ utiču&nbsp; na&nbsp; stepen potro&scaron;nje/razgradnje&nbsp; H₂O₂<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 ³⁺ i&nbsp; H ₂O_{2 ,}&nbsp; signifikantna&nbsp; količina&nbsp; H ₂O₂ostaje&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; H₂O₂ u&nbsp; toku&nbsp; Fentonovog&nbsp; (Fe ²⁺ ,&nbsp; H₂O₂ )&nbsp; i vidljivom&nbsp; svetlo&scaron;ću&nbsp; potpomognutog&nbsp; foto-Fentonovog&nbsp; (Fe²⁺,&nbsp; H ₂O₂,&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 ₂O₂ ,&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 ₂O₂ 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 />²⁺ i H ₂O₂, redom) nakon 10 min H ₂O₂je 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 ₂O₂ 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 />₂O₂ 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 ₂O₂ primenom&nbsp; Pt-C/CPE&nbsp; u&nbsp; model&nbsp; sistemima, zadovoljavajuća linearnost je postignuta u koncentracionom opseguH₂O₂od 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 ₂O₂ 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 />₂O₂deklarisanim&nbsp; od&nbsp; strane proizvođača (3%) u oba ispitivana uzorka. Pt-C/CPE je takođe testirana za praćenje koncentracije H₂O₂ 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 ₂O_{2 ,} &scaron;to je ispod dozvoljene<br />H₂O₂koncentracije 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 ₂O₂u 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 ₂O₂i&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 />₂O₂ 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 ₂O₂ 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 ₂O₂ . Pd-MWCNT-SPCE i Pd-MWCNT/SPCE su se pokazale&nbsp; pogodnim&nbsp; za&nbsp; određivanje&nbsp; H ₂O₂ 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 ₂O₂ 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 ₂O₂</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>₂<span id="cke_bm_571E" style="display: none;">&nbsp;</span>O₂ 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>₂<span id="cke_bm_577E" style="display: none;">&nbsp;</span>O₂in 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>₂<span id="cke_bm_583E" style="display: none;">&nbsp;</span>O₂consumption&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 ²⁺and H ₂O₂ ) and Fenton-&nbsp; like (Fe ³⁺and H ₂O₂ ) reagents to remove natural organic matter (NOM) at&nbsp; differentinitial concentrations of iron species, and of their molar ratios to the initial concentration of H₂O₂ . It was found that the form of Fe (Fe ²⁺ or Fe ³⁺ )and the molar&nbsp; ratio to H ₂O₂influenced the degree of the H₂O₂ decomposition in the groundwater with high NOM content. Besides, in the case of the Fenton-like process, for all initial doses of Fe ³⁺ and H<span id="cke_bm_604S" style="display: none;">&nbsp;</span>₂<span id="cke_bm_604E" style="display: none;">&nbsp;</span>O₂, 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>₂<span id="cke_bm_610E" style="display: none;">&nbsp;</span>O₂ 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;₂ 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>₂<span id="cke_bm_617E" style="display: none;">&nbsp;</span>O₂ content&nbsp; during&nbsp; the&nbsp; Fenton&nbsp; (Fe ²⁺ ,&nbsp; H <span id="cke_bm_624S" style="display: none;">&nbsp;</span>₂<span id="cke_bm_624E" style="display: none;">&nbsp;</span>O₂)&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 ^2+&nbsp; ,&nbsp; H <span id="cke_bm_631S" style="display: none;">&nbsp;</span>₂<span id="cke_bm_631E" style="display: none;">&nbsp;</span>O₂ ,&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>₂<span id="cke_bm_637E" style="display: none;">&nbsp;</span>O₂showed&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>₂<span id="cke_bm_643E" style="display: none;">&nbsp;</span>O₂&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, Fe²⁺ and H <span id="cke_bm_650S" style="display: none;">&nbsp;</span>₂<span id="cke_bm_650E" style="display: none;">&nbsp;</span>O₂, 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>₂<span id="cke_bm_656E" style="display: none;">&nbsp;</span>O₂ 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>₂<span id="cke_bm_662E" style="display: none;">&nbsp;</span>O₂ 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>₂<span id="cke_bm_668E" style="display: none;">&nbsp;</span>O₂declared 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>₂<span id="cke_bm_674E" style="display: none;">&nbsp;</span>O₂ 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>₂<span id="cke_bm_680E" style="display: none;">&nbsp;</span>O₂was&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 MnO₂-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>₂<span id="cke_bm_687E" style="display: none;">&nbsp;</span>O₂in 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 ₂ 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>₂<span id="cke_bm_694E" style="display: none;">&nbsp;</span>O₂ 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 MnO₂-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>₂<span id="cke_bm_701E" style="display: none;">&nbsp;</span>O₂oxidation 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>₂<span id="cke_bm_707E" style="display: none;">&nbsp;</span>O₂was&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>₂<span id="cke_bm_713E" style="display: none;">&nbsp;</span>O₂determination.&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 ₂O₂ 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 H₂O₂.</p>

Soil that is heavily contaminated with polycyclic aromatic hydrocarbons (PAHs) is often found at the sites of former gasworks and wood-impregnation plants. Since PAHs are toxic these sites represent a hazard to human health and the environment, and therefore they need to be treated, preferably by a method that destroys the contaminants, and thus eliminates the problem permanently. However, during biological and chemical degradation of PAHs other toxic compounds may be formed. If these transformation products are sufficiently persistent they could potentially accumulate during remedial processes. In the work underlying this thesis the degradation and transformation of PAHs were studied in three remedial processes: viz. a pilot-scale bioslurry reactor, microcosms with wood-rotting fungi and lab-scale treatments with Fenton's reagent. A group of transformation products referred to as oxygenated-PAHs (oxy-PAHs) was found to be particularly important, as these compounds are toxic and were shown to be relatively persistent in the environment. The oxy- PAHs were, for instance, found at significant concentrations in the gasworks soil used in most of the studies. This soil was highly weathered and had therefore been depleted of the more readily degradable compounds. In addition, experiments in which earthworms were exposed to the gasworks soil showed that the oxy-PAHs were more easily taken up in living organisms than PAHs. To facilitate the studies, new extraction and fractionation methods were developed. For instance, pressurized liquid extraction (PLE) was investigated for its reliability and efficiency to extract PAHs and oxy-PAHs from soil. Furthermore, a selective PLE-method was developed that can simultaneously extract and separate the PAHs and oxy-PAHs into two different fractions. This was accomplished by adding a chromatographic material (silica or Florisil) to the extraction cell. Under certain conditions all three remedial processes resulted in increasing amounts of oxy- PAHs in the soil. For example, 1-acenaphthenone and 4-oxapyrene-5-one accumulated in the bioslurry reactor. Similarly, in the soil inoculated with a white-rot fungus 9-fluorenone, benzo[a]anthracene-7,12-dione, 4-hydroxy-9-fluorenone and 4-oxapyrene-5-one accumulated. Finally, in an ethanol-Fenton treatment the concentration of some PAH-quinones increased in the soil. The results show that it might be necessary to monitor oxy-PAHs as well as PAHs during the remediation of PAH-contaminated sites. Otherwise, the soil may be considered detoxified too early in the process. In the long term it would be desirable to include analyses with sufficient marker compounds to follow the possible production and elimination of the oxy-PAHs. However, until such compounds can be identified it is suggested that contaminated soil should be screened for oxy-PAHs in general. The selective PLE-method presented in this thesis could be a useful tool for this.