doktorska disertacija
Barbara Petovar (Author), Matjaž Finšgar (Mentor)

Abstract

V doktorski disertaciji so predstavljene nove metode za določevanje težkih kovin v sledovih. Kot alternativa živosrebrni elektrodi sta bili v zadnjem desetletju predstavljeni bizmutova in antimonova elektroda, mehanizem delovanja teh elektrod pa do sedaj še ni bil pojasnjen. V doktorskem delu je predstavljena študija delovanja elektrod pri različnih pogojih elektroanalize s tehniko elektrokemijske impedančne spektroskopije (EIS). Uporabili smo nemodificirano elektrodo iz steklastega ogljika (GCE) in modificirano elektrodo z različnimi in situ pripravljenimi prevlekami na njeni površini (prevleka iz bizmuta BiFGCE in prevleka iz antimona SbFGCE) za določanje Zn(II), Cd(II) in Pb(II). Metode smo pred EIS analizo delno validirali (meja zaznavnosti, meja določljivosti, linearnost, občutljivost, točnost, natančnost). Za pripravo BiFGCE smo uporabili dve različni koncentraciji 0,5 mg/L in 1,0 mg/L Bi(III) v elektrolitu 0,1 M acetatnem pufru, za pripravo SbFGCE pa 0,5 mg/L Sb(III) v elektrolitu 0,1 M acetatnem pufru ali 0,01 M HCl. Z EIS-analizami BiFGCE pri različnih potencialih smo ugotovili, da se prevleka, nastala pri določenem potencialu elektronalaganja, enako obnaša v svojem naravnem stanju, zato je primerna za elektroanalizo. Z uporabo modelov ekvivalentnih električnih vezij (EEC) smo pridobili parametre za opis delovanja BiFGCE. Ugotovili smo, da različni dodatki težkih kovin v raztopino z elektrolitom nimajo signifikantnega vpliva na delovanje BiFGCE oziroma na kapacitivnost in polarizacijsko upornost BiFGCE. Za različne sisteme smo uporabili različne EEC in ugotovili, da delovanje BiFGCE pri določanju težkih kovin pri različnih pogojih analize (na primer potencialih elektronalaganja) ni enaki proces. Ugotovili smo, da so sistemi z 1,0 mg/L Bi(III) pri različnih potencialih elektronalaganja kinetično in difuzijsko kontrolirani procesi, sistemi z 0,5 mg/L Bi(III) so kinetično in difuzijsko kontrolirani pri potencialih, bolj negativnih od –0,6 V, pri potencialu elektronalaganja –0,6 V in bolj pozitivnih potencialih pa gre za kinetično kontrolirane procese. S SbFGCE smo v 0,01 M HCl določali Cd(II) in Pb(II), v 0,1 M acetatnem pufru pa zraven le teh še Zn(II). Z metodo EIS smo preučevali delovanje SbFGCE. Ugotovili smo, da na delovanje oziroma polarizacijsko upornost SbFGCE v acetatnem pufru koncentracija dodanih analitov nima signifikantnega vpliva pri vseh različnih potencialih EIS-analize in v HCl pri potencialih EIS-analize enakih potencialom elektronalaganja. Z uporabo EEC modelov smo ugotovili, da so pri najbolj negativnih potencialih elektronalaganja (–1,1 V za SbFGCE v HCl in –1,2 V za SbFGCE v acetatnem pufru) sistemi pod kinetično kontroliranimi procesi ne glede na prisotnost in koncentracijo analitov. Zaradi dobrih analitskih lastnosti BiFGCE in SbFGCE smo razvili nove elektrode z različnimi kombinacijami bizmutove in antimonove prevleke na GCE (BiSbFGCE) ter skupno masno koncentracijo Bi(III) in Sb(III) 0,5 mg/L ali 1,0 mg/L. 22 različnih metod smo delno validirali za določanje Zn(II), Cd(II) in Pb(II) v 0,1 M acetatnem pufru. Ugotovili smo, da imajo določene metode širše linearno območje in boljšo občutljivost za določanje analitov v primerjavi z drugimi kombiniranimi BiSbFGCE ali samo BiFGCE ali SbFGCE. Večina metod je za določanje Cd(II) in Pb(II) v okviru izbranih kriterijev točnosti in natančnosti. Potem smo optimizirali še čas elektronalaganja prevleke na GCE in ponovno delno validirali izbrane metode z optimiziranim časom elektronalaganja. Z optimizacijo smo dosegli nižje meje zaznavnosti in določljivosti ter boljšo občutljivost za določanje analitov. Na GCE smo razvili tudi nov senzor za detekcijo vodikovega peroksida. Gre za nov pristop priprave tovrstnega senzorja. Na GCE smo nanesli nov material iz nanodelcev grafena (GNP) brez uporabe encimov. Z amperometrično analizo pripravljenega senzorja smo potrdili, da je redukcija H2O2 difuzijsko kontroliran proces in da je GNP/GCE selektivna za H2O2.

Keywords

anodna striping voltametrija;elektrokemijska impedančna spektroskopija;vodikov peroksid;amperometrija;BiFGCE;SbFGCE;BiSbFGCE;GNP/GCE;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [B. Petovar]
UDC: 544.6.076.32:542.87:543.42(043.3)
COBISS: 22683926 Link will open in a new window
Views: 1675
Downloads: 240
Average score: 0 (0 votes)
Metadata: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Other data

Secondary language: English
Secondary title: Developement of modified glassy carbon electrodes for trace heavy metal detection and hydrogen peroxide analysis
Secondary abstract: In the doctoral dissertation new methods for trace heavy metal detection are presented. In the last decade bismuth and antimony electrodes as an alternative to mercury electrode were presented, but the mechanism and working of these electrodes was not yet explained. In the doctoral thesis, a study of electrode behavior under various electroanalysis conditions by electrochemical impedance spectroscopy (EIS) is presented. An unmodified glassy carbon electrode (GCE) and in situ modified glassy carbon electrodes (bismuth modified BiFGCE or antimony modified SbFGCE) for Zn(II), Cd(II) and Pb(II) determination were used. Before the EIS analysis the methods were partially validated (limit of detection, limit of quantification, linear concentration range, sensitivity, accuracy, precision). For BiFGCE preparation, two different Bi(III) concentrations 0.5 mg/L and 1.0 mg/L in an electrolyte of 0.1 M acetate buffer were used. For the SbFGCE preparation the Sb(III) concentration was 0.5 mg/L in the electrolyte of 0.1 M acetate buffer or 0.01 M HCl. By using EIS for BiFGCE at different potentials it was found, that the films on the GCE prepared at certain deposition potentials have the same behaviour in their natural state, therefore they are suitable for electroanalysis. Using the equivalent electrical circuit (EEC) models the parameters for descripting the working of BiFGCE are obtained. We found out, that various additions of heavy metals in the electrolyte solution do not have a significant effect on the BiFGCE behaviour or on the capacitance and resistance of BiFGCE. Different EEC were used for fitting the results of different systems. We found out, that the behaviour of BiFGCE for heavy metal determination at different electroanalysis conditions (e.g. different deposition potentials) is not the same process. The systems with 1.0 mg/L Bi(III) at different deposition potentials are kinetic and diffusion-controlled processes and systems with 0.5 mg/L Bi(III) are kinetic and diffusion-controlled at potentials more negative than –0.6 V and only kinetic-controlled processes at deposition potential –0.6 V and more positive potentials. SbFGCE was used for Cd(II) and Pb(II) determination in 0.01 M HCl and also Zn(II) in 0.1 M acetate buffer. The behaviour of SbFGCE was studied using EIS. It was found out, that the concentration of analytes does not affect the resistance of SbFGCE in acetate buffer at different EIS potentials and in HCl at EIS potentials that are the same as deposition potentials. Using EEC we found out that the systems are under kinetic-controlled processes regardless of the presence and concentration of analytes at the most negative deposition potentials (–1.1 V for SbFGCE in HCl and –1.2 V for SbFGCE in acetate buffer). Due to the good analytical performances of BiFGCE and SbFGCE new electrodes, modified with combinations of bismuth and antimony film on GCE (BiSbFGCE) were developed. The total mass concentration of Bi(III) and Sb(III) in different films was 0.5 mg/L or 1.0 mg/L. 22 different methods were partially validated for Zn(II), Cd(II) and Pb(II) determination in 0.1 M acetate buffer. It was found that certain methods have wider linear concentration range and better sensitivity for analytes determination compared with other combined BiSbFGCE or pure BiFGCE or pure SbFGCE. Most of the developed methods for Cd(II) and Pb(II) determination are within the desired criteria for accuracy and precision. The deposition time was optimized and the certain methods were partially validated with the optimized deposition time. With deposition time optimisation lower limits of detection and quantification and better sensitivity were achieved. On GCE substrat a new non-encimatic sensor for hydrogen peroxide detection was developed. This is a new approach to prepare such sensor. A new material from graphene nanoparticles (GNP) was applied on the GCE surface. It was confirmed that the GNP/GCE is selective for H2O2.
Secondary keywords: anodic stripping voltammetry;electrochemical impedance spectroscopy;BiFGCE;SbFGCE;BiSbFGCE;GNP/GCE;hydrogen peroxide;amperometry;Težke kovine;Disertacije;Določanje;Elektrode;
Type (COBISS): Doctoral dissertation
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: XVII, 110 str.
ID: 11151424