Ana Kroflič

National Institute of Chemistry

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Irena Grgić

National Institute of Chemistry

MŠ

Martin Šala

National Institute of Chemistry

Sanja Frka

Rudjer Boskovic Institute

Marija Bešter‐Rogač

University of Ljubljana

Matej Huš

National Institute of Chemistry

Kristijan Vidović

National Institute of Chemistry

Miha Grilc

National Institute of Chemistry

Blaž Likozar

National Institute of Chemistry

Irena Ciglenečki

Rudjer Boskovic Institute

Monika Ogrizek

National Institute of Chemistry

Cooperative Institutions

University of Ljubljana

National Institute of Chemistry

Leibniz Institute for Tropospheric Research

Centre National de la Recherche Scientifique

Jožef Stefan Institute

Paul Scherrer Institute

University of Nova Gorica

Jožef Stefan International Postgraduate School

Rudjer Boskovic Institute

University of California, Berkeley

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Influence of the alkyl chain length, temperature, and added salt on the thermodynamics of micellization: Alkyltrimethylammonium chlorides in NaCl aqueous solutions

The Journal of Chemical Thermodynamics (2011)

Ana Kroflič Bojan Šarac Marija Bešter‐Rogač

Isothermal Titration Calorimetry

Thermodynamics of micellization

Isothermal process

Cationic polymerization

10.1016/j.jct.2011.05.015

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Citations (36)

Acute toxicity of emerging atmospheric pollutants from wood lignin due to biomass burning

Journal of Hazardous Materials (2017)

Maryline Pflieger Ana Kroflič

Guaiacol

10.1016/j.jhazmat.2017.05.023

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Citations (37)

Selective Glucose Oxidation to Glucaric Acid Using Bimetallic Catalysts: Lattice Expansion or Electronic Structure Effect?

Žan Lavrič Janvit Teržan Ana Kroflič Janez Zavašnik Joanna Elżbieta Olszowka

Our study presents a comprehensive approach for the selective oxidation of glucose to glucaric acid (GA) by heterogeneous catalysis. We have synthesized and characterized Au/ZrO2, AuCu/ZrO2 and AuPt/ZrO2 catalysts using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and oxygen pulse chemisorption (OPS) techniques. Combining experimental observations with in-depth density functional theory (DFT) studies, we found that bimetallic catalysts form alloys, which exhibit different characteristics than monometallic counterparts for the given reaction. We performed batch reactions, varying temperature and oxygen pressure, and used the data to construct a predictive microkinetic model. As it turned out, AuPt/ZrO2 showed the highest selectivity, yielding 32 % of GA at 100 °C and 30 barg O2. Our results provide valuable insights for the developing of efficient catalysts and point out the bottlenecks for the oxidation of glucose to GA.

Bimetallic strip

Lattice (music)

10.2139/ssrn.4584995

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Critical review on the development of analytical techniques for the elemental analysis of airborne particulate matter

Trends in Environmental Analytical Chemistry (2022)

Monika Ogrizek Ana Kroflič Martin Šala

Among all environmental pollutants, particulate matter (PM) poses the major threat to our health. These tiny airborne particles vary in shape and composition, which is reflected in their hazardous potential. The particles are small enough to penetrate deep into the lungs and even enter the bloodstream, causing severe diseases. Therefore, their regular monitoring is required. Toxic metals and other elements are often measured by regulatory agencies as well as in research laboratories, either to compare ambient concentrations with prescribed limit values or to study provenance of air pollution sources in order to target PM pollution mitigation strategies. The most established method for the determination of regulated Pb, Cd, As, Ni and other elements in PM is microwave digestion inductively coupled plasma mass spectrometry (MW/ICPMS), whereas X-ray fluorescence (XRF) techniques have also often been used, especially in research. In this review paper we critically assess these two and three other analytical techniques (i.e., LA-ICPMS, PIXE and INAA) for element determination in PM deposited on filter media. All aspects from sample treatment to measurement range and limitations, costs and waste management are considered. In conclusion we identify XRF and LA-ICPMS as two promising surface techniques for the analysis of a PM deposit on a filter, which could replace the laborious wet MW/ICPMS method, which is – considering its wide use, very incriminating to the environment. In short, EDXRF is the cheapest, simplest for use and already customized for PM samples, whereas LA-ICPMS is promising, but still needs some development in the direction of autosamplers and matrix-matched standards for calibration.

10.1016/j.teac.2022.e00155

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Citations (24)

Kinetics and product identification of water-dissolved nitroguaiacol photolysis under artificial sunlight

Frontiers in Chemistry (2023)

Ajda Delić Urša Skube Martin Šala Ana Kroflič

Nitroguaiacols are typical constituents of biomass-burning emissions, including absorbing aerosols which contribute to climate change. Although they are also harmful to humans and plants, their atmospheric fate and lifetimes are still very speculative. Therefore, in this work, the photolysis kinetics of aqueous-phase 4-nitroguaiacol (4NG) and 5-nitroguaiacol (5NG), and the resulting photo-formed products were investigated under artificial sunlight, observing also the effect of sunlight on the absorption properties of the solutions. We found the photolysis of 5NG slower than that of 4NG, whereas the absorbance in the visible range prevailed in the 5NG solutions at the end of experiments. Although we identified dinitroguaiacol as one of the 4NG photolysis products, which increased light absorption of 4NG-containing solutions, considerably more chromophores formed in the 5NG photolyzed solutions, implying its stronger potential for secondary BrC formation in the atmosphere. In general, denitration, carbon loss, hydroxylation, nitration, and carbon gain were characteristic of 4NG phototransformation, while carbon loss, hydroxylation, and carbon gain were observed in the case of 5NG. The photolysis kinetics was found of the first order at low precursor concentrations (<0.45 mM), resulting in their lifetimes in the order of days (125 and 167 h illumination for 4NG and 5NG, respectively), which suggests long-range transport of the investigated compounds in the atmosphere and proposes their use as biomass-burning aerosol tracer compounds.

Absorbance

Carbon fibers

10.3389/fchem.2023.1211061

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Nighttime Aqueous-Phase Formation of Nitrocatechols in the Atmospheric Condensed Phase

Environmental Science & Technology (2018)

Kristijan Vidović Damjan Lašič Jurković Martin Šala Ana Kroflič Irena Grgić

Yellow-colored methylnitrocatechols (MNC) contribute to the total organic aerosol mass and significantly alter absorption properties of the atmosphere. To date, their formation mechanisms are still not understood. In this work, the intriguing role of HNO2 (catalytic and oxidative) in the dark transformation of 3-methylcatechol (3MC) under atmospherically relevant aqueous-phase conditions is emphasized. Three possible pathways of dark 3-methyl-5-nitrocatechol and 3-methyl-4-nitrocatechol formation, markedly dependent on reaction conditions, were considered. In the dominant pathway, HNO2 is directly involved in the transformation of 3MC via consecutive oxidation and conjugated addition reactions (nonradical reaction mechanism). The two-step nitration dominates at a pH around the pKa of HNO2, which is typical for atmospheric aerosols, and is moderately dependent on temperature. Under very acidic conditions, the other two nitration pathways, oxidative aromatic nitration (electrophilic) and recombination of radical species, gain in importance. The predicted atmospheric lifetime of 3MC according to the dominant mechanism at these conditions (2.4 days at pH 4.5 and 25 °C) is more than 3-times shorter than that via the other two competitive pathways. Our results highlight the significance of a catechol oxidation-conjugated addition reaction in a nighttime secondary nitroaromatic chromophore formation in the atmosphere, especially in polluted environments with high NOx concentrations and relatively acidic particles (pH around 3).

Aqueous two-phase system

Chromophore

Catechol

10.1021/acs.est.8b01161

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Citations (90)

Selective Glucose Oxidation to Glucaric Acid Using Bimetallic Catalysts: Lattice Expansion or Electronic Structure Effect?

Žan Lavrič Janvit Teržan Ana Kroflič Janez Zavašnik Joanna Elżbieta Olszowka

Our study presents a comprehensive approach for the selective oxidation of glucose to glucaric acid by heterogeneous catalysis. We have synthesised and characterised Au/ZrO2, AuCu/ZrO2 and AuPt/ZrO2 catalysts using XRD, TEM, XPS and oxygen pulse chemisorption techniques. Combining experimental observations with in-depth DFT studies, we found that bimetallic catalysts form alloys and AuCu exhibits oxygen scission leading to overoxidation of C6 compounds. We performed batch reactor experiments at temperatures of 60-120 °C and pressures of 18-30 barg O2. Using the data, we constructed a predictive microkinetic model, which showed that the AuPt catalyst exhibited the highest selectivity, yielding 32% glucaric acid at 100 °C and 30 barg O2. However, at higher temperatures, over-oxidation led to increased formation of tartaric acid, tartronic acid, glycolic acid, oxalic acid and formic acid. Our results provide valuable insights for the development of efficient catalysts for the oxidation of glucose to glucaric acid.

Bimetallic strip

Lattice (music)

10.2139/ssrn.4505479

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Citations (0)

Seasonal variability of nitroaromatic compounds in ambient aerosols: Mass size distribution, possible sources and contribution to water-soluble brown carbon light absorption

Chemosphere (2022)

Sanja Frka Martin Šala Helena Brodnik Bogdan Štefane Ana Kroflič

Levoglucosan

Seasonality

10.1016/j.chemosphere.2022.134381

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Citations (25)

Thermodynamic Characterization of 3-[(3-Cholamidopropyl)-dimethylammonium]-1-propanesulfonate (CHAPS) Micellization Using Isothermal Titration Calorimetry: Temperature, Salt, and pH Dependence

Langmuir (2012)

Ana Kroflič Bojan Šarac Marija Bešter‐Rogač

A systematic investigation of the micellization process of a biocompatible zwitterionic surfactant 3-[(3-cholamidopropyl)-dimethylammonium]-1-propanesulfonate (CHAPS) has been carried out by isothermal titration calorimetry (ITC) at temperatures between 278.15 K and 328.15 K in water, aqueous NaCl (0.1, 0.5, and 1 M), and buffer solutions (pH = 3.0, 6.8, and 7.8). The effect of different cations and anions on the micellization of CHAPS surfactant has been also examined in LiCl, CsCl, NaBr, and NaI solutions at 308.15 K. It turned out that the critical micelle concentration, cmc, is only slightly shifted toward lower values in salt solutions, whereas in buffer media it remains similar to its value in water. From the results obtained, it could be assumed that CHAPS behaves as a weakly charged cationic surfactant in salt solutions and as a nonionic surfactant in water and buffer medium. Conventional surfactants alike, CHAPS micellization is endothermic at low and exothermic at high temperatures, but the estimated enthalpy of micellization, ΔHM0, is considerably lower in comparison with that obtained for ionic surfactants in water and NaCl solutions. The standard Gibbs free energy, ΔGM0, and entropy, ΔSM0, of micellization were estimated by fitting the model equation based on the mass action model to the experimental data. The aggregation numbers of CHAPS surfactant around cmc, obtained by the fitting procedure also, are considerably low (nagg ≈ 5 ± 1). Furthermore, some predictions about the hydration of the micelle interior based on the correlation between heat capacity change, Δcp,M0, and changes in solvent-accessible surface upon micelle formation were made. CHAPS molecules are believed to stay in contact with water upon aggregation, which is somehow similar to the micellization process of short alkyl chain cationic surfactants.

Isothermal Titration Calorimetry

Thermodynamics of micellization

Aggregation number

10.1021/la302133q

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Citations (51)

Evaluation of 213-nm laser as an affordable alternative for the green elemental characterization of particulate matter on quartz fibre filters by laser ablation ICPMS

Air Quality Atmosphere & Health (2023)

Monika Ogrizek Ana Kroflič Tomáš Vaculovič Markéta Holá Martin Šala

Laser Ablation

Breath gas analysis

10.1007/s11869-023-01338-9

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Citations (0)