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Title:Določevanje železa v naravnih vodah s tehniko FIA-TLS
Authors:Tomsič, Gaja (Author)
Franko, Mladen (Mentor) More about this mentor... New window
Korte, Dorota (Mentor) More about this mentor... New window
Files:.pdf Gaja_Tomsic.pdf (2,30 MB)
 
Language:Slovenian
Work type:Master's thesis (m2)
Tipology:2.09 - Master's Thesis
Organization:FZO - Faculty of Environmental Sciences
Abstract:Vodni organizmi potrebujejo železo za bistvene metabolne procese. Vendar pa se večina raztopljenega železa v vodi, ki ni vezana na organske molekule ali kompleksirana z anorganskimi ligandi, oksidira v železove ione Fe(III) in tvori oborino Fe(OH)3. Zato je aktivnost biomase na vodni gladini pogosto omejena z razpoložljivostjo raztopljenega železa, ki je lahko nižja od 1 nM. To dejstvo lahko vpliva tudi na širše okolje, saj ima vpliv na hitrost fiksiranja CO2 zaradi fotosinteze avtotrofne biomase. Določanje elementov v sledovih, med katerimi je tudi železo, predstavlja zaradi kompleksnosti naravne vode izziv. Določitev koncentracije železa je v preteklosti zahtevala predhodno koncentracijo vzorca z ekstrakcijo s topilom. V tem delu poročamo o rezultatih spektrometrije s toplotnimi lečami s pretočno injekcijsko analizo, ki ne potrebuje predkoncentracije železa v vzorcu. Koncentracije železa v različnih redoks oblikah smo določali s pretočno injekcijsko analizo (FIA) z uporabo 1,10 - fenantrolina, ki kompleksira železove Fe(II) ione v stabilen kompleks z absorpcijskim maksimumom pri 508 nm. Skupno količino raztopljenega železa (Fe(II) in Fe(III)) smo določili po redukciji Fe(III) iona v Fe(II) z askorbinsko kislino. V sistemu FIA smo za detekcijo uporabili spektrometer s toplotnimi lečami (TLS); tipalni žarek je imel valovno dolžino 633 nm, vzbujevalni pa 450 nm ali 530 nm. Posledica absorpcije svetlobe vzbujevalnega žarka je segrevanje vzorca zaradi neradiacijske relaksacije absorbirane energije. Tvori se toplotna leča (TL). Detekcija temelji na razprševanju tipalnega žarka na TL. Analize vzorcev smo izvajali v »šaržnem« in »on-line« načinu. Z »on-line« konfiguracijo (1,10 - fenantrolin je sestavljal nosilno raztopino za FIA) smo lahko injicirali vzorce brez kakršnekoli predhodne priprave ali dodajanja reagentov, razen askorbinske kisline pri določevanju skupnega železa. V tem magistrskem delu smo primerjali spodnje meje detekcije (LOD) različnih tehnik in pogojev (valovne dolžine laserske svetlobe in koncentracija nosilne raztopine v pretočnem sistemu) s ciljem, da bi dosegli najboljšo občutljivost za železove ione. FIA-TLS je primerna tudi za tehniko standardnega dodatka. Uporabnost in pravilnost FIA-TLS smo preverili z določevanjem koncentracij železa v rečni vodi.
Keywords:železove zvrsti, pretočna injekcijska analiza (FIA), spektrometrija s toplotnimi lečami (TLS)
Year of publishing:2019
Source:Nova Gorica
COBISS_ID:5329147 Link is opened in a new window
URN:URN:SI:UNG:REP:PCBPBMCO
Views:418
Downloads:27
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Secondary language

Language:English
Title:Determination of iron in natural waters by FIA-TLS
Abstract:Aquatic organisms need iron as a vital requisite for essential metabolic processes. However, most of the dissolved iron in seawater, that is not bonded to organic molecules or complexed with inorganic ligands, is oxidised to ferric ions Fe(III) and precipitates as Fe(OH)3. For that reason, water surface productivity is often limited by dissolved iron availability, which can be lower than 1 nM. This fact can furthermore have consequences on broader environment; it can affect the rates of CO2 fixation during photosynthesis of the autotrophic biomass. The determination of trace elements, among which there is also iron, is due to the complexity of natural water challenging. The determination of iron concentration historically required preconcentration of the sample with solvent extraction. In this work we report on results of thermal lens spectrometry coupled with flow injection analysis, a method that does not depend upon preconcentration of iron in the sample. The concentrations of iron redox species was determined by flow injection analysis (FIA) using 1,10 - phenanthroline, that binds ferrous Fe(II) ions to form a stable complex with an absorption maximum at 508 nm. The total amount of dissolved iron (ferric and ferrous ions) was analysed after the reduction of Fe(III) ions to Fe(II) with ascorbic acid. In FIA system the detection was performed by a thermal lens spectrometer TLS using a 633 nm probe laser and 450 or 530 nm pump laser beam. As the consequence of the absorption of the pump beam the sample is heated because of non-radiative relaxation of the absorbed energy. A so called thermal lens (TL) is formed. The detection is based on defocusing the probe beam by TL. The analysis was performed both in a batch mode and in an on-line mode. With the on-line configuration we were able to inject the samples without any preparation or addition of reagents (1,10 - phenanthroline was the carrier for FIA), except for ascorbic acid for the determination of total iron. In this work we compared the limits of detection (LOD) of different techniques and their different versions (laser wavelength, concentration of carrier in the online mode) to reach the best sensitivity towards iron species. FIA-TLS is suitable also for standard addition technique. Its usability and reliability were checked by determining the concentrations of iron in river water.
Keywords:iron species, flow injection analysis (FIA), thermal lens spectrometry (TLS)


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