Karakterizacija interakcije metala u tragovima s organskim ligandima UV/Vis spektrometrijom

master's thesis

• Title (english): Characterization of interaction between trace metals and organic ligands by UV/Vis spectrometry
• Author: Saša Marcinek
• Mentor: Tomislav Bolanča (mentor)
• Committee member: Tomislav Bolanča (predsjednik povjerenstva)
• Committee member: Šime Ukić (član povjerenstva)
• Committee member: Ema Horak (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2017-07-10, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry; Analytic Chemistry

Abstract

Metali u tragovima su u prirodnim vodama raspodijeljeni u različite kemijske vrste (specije). Određivanje njihove raspodjele (specijacija) ključno je za bolje razumijevanje biogeokemijskog ciklusa i utjecaja u vodenom ekosustavu. Mnogi metali su većinom vezani u vrlo stabilne komplekse s organskim ligandima. U ovom radu interakcija metala u tragovima s organskim ligandima ispitana je UV/Vis spektrometrijom, na primjeru interakcije bakra s EDTA kao poznatim sintetskim organskim ligandom, s kromofornom otopljenom organskom tvari (CDOM) iz izoliranih frakcija riječne i morske vode, te s prirodnim organskim ligandima iz uzorka vode rijeke Save. Prilikom obrade spektara korištene su gotovo sve metodologije za određivanje specifičnih parametara koje su danas raspoložive u literaturi, a koje su implementirane u posebno za tu svrhu razvijeni program (ASFit). Pokazana je važnost izbora komponenata koje se dodaju u otopinu za mjerenje apsorbancije te utjecaj promjene pH vrijednosti na topljivost bakra, apsorpciju same organske tvari kao i interakciju bakra s ispitivanom organskom tvari. Povećanjem koncentracije bakra u otopini došlo je do promjena u apsorpcijskim spektrima svih ispitivanih organskih tvari s apsorpcijskim maksimumima (odnosno minimumima kod riječne huminske kiseline) na različitim valnim duljinama. Parametri određeni obradom apsorpcijskih spektara dobivenih titracijom dinatrijeve soli EDTA i diferencijalnih apsorpcijskih spektara modelnih otopina pokazali su statistički vrlo značajnu linearnu ovisnost o koncentraciji nastalog kompleksa procijenjenu pomoću Visual MINTEQ programa, dok uzorak rijeke Save nije bio u korelaciji s procijenjenim vrijednostima. Istraživanja su pokazala da se derivativni i diferencijalni spektri, te karakteristični parametri obrade spektara (maksimum prve derivacije, diferencijalni apsorpcijski koeficijent na valnoj duljini apsorpcijskog maksimuma, diferencijalni spektralni nagib, omjer diferencijalnih spektralnih nagiba i visina Gaussovih krivulja) mogu uspješno koristiti za istraživanje interakcije metala u tragovima s organskim ligandima. Međutim, moguću primjenu UV/Vis spektrometrije u tu svrhu, u realnim prirodnim uzorcima, potrebno je detaljnije istražiti.

Abstract (english)

Trace metals in natural waters are distributed in different chemical forms. Measurements of individual form are required to understand and predict their fate and effect on aquatic species. Major fraction of many trace metals are present as complexes with ligands from natural organic matter. In this work UV/Vis spectrometry was used to examine interactions of copper with known synthetic ligand (EDTA), with chromophoric dissolved organic matter (CDOM) isolated from river and marine water and with natural organic ligands from Sava River. For characterization of obtained absorbance spectra were used different methods and parameters that are implemented in all-in-one computer program (ASFit) designed for this purpose. It was shown that careful selection of components added to the solution for absorbance measurements is of great importance, same as maintaining constant pH value since copper solubility, its interactions with organic matter and absorption of organic matter itself is strongly pH dependent. All absorbance measurements of copper interactions with organic ligands have shown differences in the spectral signals between the original spectra and those changed upon the increase of copper concentrations, with peaks located at different wavelengths. Parameters derived from absorbance measurements of copper interactions with organic ligands were compared with bound copper estimated based on Visual MINTEQ calculations. This examination have shown that parameters derived from EDTA derivative spectra and model solutions differential spectra strongly correlate with concentration of bound copper, unlike the parameters derived from changes in absorbance spectra of Sava River sample. This study have shown that derivative and differential spectra, along with the characteristic spectral parameters (maximum of first derivation, differential absorption coefficient at absorption peak wavelength, differential spectral slope, differential spectral slope ratio and Gaussian curve height) can be used to generate information concerning the nature of interaction of trace metals with organic ligands. However application of UV/Vis spectrometry for this purpose in real natural samples needs to be further explored.

• Keywords: UV/Vis spektrometrija; apsorpcija; metali u tragovima; organski ligandi; kompleksiranje; ASFit; Visual MINTEQ
• Keywords (english): UV/Vis spectrometry; absorbance; trace metals; organic ligands; complexation; ASFit; Visual MINTEQ
• Language: croatian
• URN:NBN: urn:nbn:hr:149:899776
• Study programme: Title: Environmental Engineering - Graduate study; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka ekoinženjerstva (magistar/magistra inženjer/inženjerka ekoinženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-11-07 09:28:09