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2. TLS Detection in Liquid Chromatography, Flow Injection Analysis and Microfluidic Systems for Food Quality Control and Biomedical DiagnosticsMladen Franko, 2023, invited lecture at foreign university Abstract: The basics of thermal lens spectrometry (TLS) and TLS microscopy (TLM) will be explained considering in particular the dependence of the thermal lens signal on the excitation power, thermo-optical properties of the sample, as well as sample flow and photostability of the analyte, with particular focus on the TLS enhancement factor, sensitivity and sample throughput of TLS and TLM measurements.
Examples of applications will include most notable achievements of TLS and TLM measurements in liquid chromatography (detection of bilirubin and biliverdin in blood plasma, bilirubin in vascular endothelial cells), flow injection analysis (organophosphate insecticides and allergens in foodstuffs) and microfluidics (high throughput determination of Cr(VI), microcystin, HPV virus antibodies, and biomarkers of acute kidney injury).
Before the concluding remarks, recent progress in multi-pass mode-mismatched TLS instrumentation and applications of incoherent light sources will be presented s part of the future outlook for TLS and TLM techniques.
Keywords: Spektrometrija TLS, TLM, chromatography, microfluidics, FIA
Published in RUNG: 14.11.2023; Views: 1874; Downloads: 8
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3. Effects of Photodegradation in TLS Measurements: Troubleshooting and Applications in Photochemistry and PhotocatalysisMladen Franko, 2023, published scientific conference contribution abstract (invited lecture) Abstract: Most analytical applications of thermal lens spectrometry (TLS) and related theoretical models consider absorbance of the sample constant during a single excitation by the pump laser beam. For photolabile analytes intensive excitation light can cause photodegradation, which significantly affects the results of TLS measurements.
Theoretical models have been developed to account for changes in concentration and consequent changes in absorbance, caused by chemical reactions of different orders. Furthermore, abnormal TLS signal transients were observed for fast photochemical reactions on millisecond time scale, and the contributions of photodegradation as well as molecular diffusion were analyzed in detail. It has also been demonstrated that such effects can be reduced by performing TLS measurements in flowing systems such as in the case of flow injection analysis (FIA) or microfluidics.
These findings were utilized to study the kinetics of chemical reactions, processes such as photostability of the soybean oil and thermal stability of biodiesel, or to improve the sensitivity of TLS detection in case of photolabile analytes. Furthermore, in combination with the concept of biomolecular recognition, FIA-TLS was exploited to study the efficiency of photocatalytic degradation of some neurotoxic substances such as organophosphate insecticides and revealed the formation of even more toxic degradation products. High sensitivity of TLS has enabled discrimination between photocatalytic and photosensitization mechanisms in photocatalytic degradation of textile dyes as well as between photodegradation and photocatalysis as will be demonstrated by the results of latest research in this field.
Keywords: Spektrometrija TLS, fotolabilnost, CrIVI), fotokataliza, fotorazgradnja
Published in RUNG: 23.10.2023; Views: 2572; Downloads: 0
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4. Recent Progress and Applications of Thermal Lens Spectrometry and Photothermal Beam Deflection Techniques in Chemical Analysis and Materials' CharacterizationMladen Franko, 2023, invited lecture at foreign university Abstract: Initially the theoretical background relevant to recent developments of thermal lens spectrometry (TLS) which include TLS detection in liquid chromatography and in microfluidic flow injection analysis (μFIA) and to non-contact and non-destructive characterization of composite materials by beam deflection spectrometry (BDS) is presented. The advantages and basic characteristics of the TLS and BDS techniques are illustrated by presenting applications such as the determination of free bilirubin in endothelial cells by HPLC-TLS, studies of diffusion in Taylor-type microfluidic flows by thermal lens microscopy (TLM), μFIA-TLM detection of microcystin-LR and Cr(VI) in waters, and by the dept profiling of multi-layered coatings of orthopaedic implants.
In the main part of the presentation the results of joint MU-UNG research are presented with emphasis on BDS and TLS characterisation of biocomposite materials from cellulose and chitosan or keratin with added Ag nanoparticles, sporopollenin capsules or antibiotics. The focus is on BDS determination of thermal parameters including thermal diffusivity and related properties relevant for medical applications, such as porosity and surface roughness, as well as on the TLS detection of Ag and other nanoparticles applied in studies of nanoparticle leaching from biocomposites.
Keywords: Optotermična spektrometrija, TLS, BDS, kemijska analiza, karakterizacija materialov, biokompoziti
Published in RUNG: 23.10.2023; Views: 1583; Downloads: 6
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6. Trajnostni biokompozitni materiali iz naravnih polimerov in njihova neporušna karakterizacija z optotermičnimi tehnikamiMladen Franko, other performed works Abstract: Predstavljene so osnove zelene sinteze novih biokompozitnih materialov iz kombinacij celuloze s hitosanom ali keratinom in sporopoleninom ter njihove protimikrobne lastnosti in adsorpcijske sposobnosti za čiščenje vode. Pomembna lastnost biokompozitov z vidika njihove uporabnosti je tudi poroznost, ki jo lahko določamo neporušno in nekontaktno s tehniko optotermičnega odlkona. Ta omogoča določevanje toplotne difuzivnosti materialov ter preko nje poroznosti, kot tudi globinske porazdelitve v material vgrajenih snovi, ki izboljšujejo njegove lastnosti.
Keywords: Biokompoziti, celuloza, hitosan, keratin sporopolenin, toplotna difuzivnost, poroznost, optotermična spektrometrija
Published in RUNG: 11.05.2023; Views: 2677; Downloads: 0
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7. Določevanje železa v naravnih vodah s tehniko FIA-TLSGaja Tomsič, 2019, master's thesis 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)
Published in RUNG: 19.02.2019; Views: 5955; Downloads: 146
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8. Hemichrome Determination by Thermal Lensing with Polyethylene Glycols for Signal Enhancement in Aqueous SolutionsViktoriya Galimova, Mladen Franko, Mikhail Proskurnin, Mingqiang Liu, 2018, original scientific article Abstract: The thermal lens technique is proposed for the determination of total hemoglobin in the form of reversible hemichrome. The conditions were optimized (concentration of sodium dodecyl sulfate, 2 mM) to attain the maximum sensitivity with the use of polyethylene glycols as signal enhancers. For polyethylene glycols with molecular weights 1500–35000 Da in a concentration range of 5–15% w/w (5–25 mM), the influence on thermal lens signal enhancement was estimated. It is shown that the use of 5% w/w polyethylene glycol 2000 provides the maximum increase in the thermal lens enhancement factor (by 40%) in comparison with unmodified aqueous solutions. The detection limit of iron(II) tris(1,10-phenanthrolinate) as a model system is 60 nM. Under these conditions, the thermal lens detection limit of hemichrome is 10 nM, which shows a 15-fold enhancement compared to spectro- photometry. Modification of the medium with polyethylene glycols decreases the limit of detection of hemichrome determination by 15% in comparison with unmodified aqueous solutions due to better reproducibility for the range of concentrations from 0.02 to 0.9 μM.
Keywords: Hemoglobin, hemikrom, optotermična spektroskopija, etilenglikol, spektrometrija s toplotnimi lečami
Published in RUNG: 16.04.2018; Views: 4996; Downloads: 0
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9. Priprava in izvedba preizkušanja v okviru razvoja novega drsnega obroča : Diplomsko deloSimon Majnik, 2018, undergraduate thesis Abstract: Razvoj na področju avtomobilske industrije in transporta je v zadnjem desetletju usmerjen predvsem v zamenjavo pogonskega agregata, torej motorja z notranjim izgorevanjem, z okolju prijaznejšimi elektromotorji. Uporaba elektrike kot vira energije pa zahteva ustrezne rešitve prenosa elektrike, za kar skrbijo drsni obroči. Tudi drsni obroči morajo za ustrezno opravljanje svoje funkcije prenosa elektrike med gibanjem izpolnjevati materialne, trdnostne in funkcionalne zahteve. Vsebina diplomske naloge je tako vezana na opis delovanja drsnih obročev in preučitev zahtev kupca o potrebnih lastnostih na novo razvitega drsnega obroča za pogon električnega osebnega avtomobila. Na podlagi teh zahtev je potrebno nato definirati in izvesti preizkuse lastnosti, s katerimi zagotovimo izpolnjevanje zahtev izdelka. Namen diplomskega dela je bil predstaviti teoretične osnove delovanja in izvedb drsnih obročev, opisati preizkuse lastnosti in funkcionalnosti drsnih obročev ter predstaviti rezultate preizkušanja na novo razvitega drsnega obroča vključno z alternativno tehnologijo tesnjenja kontaktne žice. V diplomskem delu so tako predstavljeni rezultati preizkusov tesnosti žice z uporabo različnih materialov žice in s primerjavo različnih tehnologij tesnjenja žice ter rezultati preizkušanja tesnosti po izpostavljenosti agresivnim medijem. V drugem delu so prestavljeni rezultati preizkušanja zvarov na zvarjencih, ki so sestavni del drsnega obroča, z uporabo dveh različnih testnih metod. Rezultati diplomskega dela kažejo, da je nova tehnologija izdelave tesnil iz tesnilne mase primerna za uporabo v primeru drsnih obročev, medtem ko na mestu zvara električnih kontaktov najboljšo trdnost, določeno z dvema različnima testnima metodama, dosežemo z uporabo spajkalne paste in časa varilnega pulza 125 ms.
Keywords: Drsni obroč, električni kontakti, test tesnosti, masna spektrometrija, uporovno varjenje, o-tesnilo, x-tesnilo
Published in RUNG: 26.02.2018; Views: 5479; Downloads: 269
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