1. Periodic arrays of chiral domains generated from the self-assembly of micropatterned achiral lyotropic chromonic liquid crystalGeonhyeong Park, Simon Čopar, Ahram Suh, Minyong Yang, Uroš Tkalec, Dong Ki Yoon, 2020, izvirni znanstveni članek Opis: Achiral building blocks forming achiral structures is a common occurrence in nature, while chirality emerging spontaneously from an achiral system is usually associated with important scientific phenomena. We report on the spontaneous chiral symmetry-breaking phenomena upon the topographic confinement of achiral lyotropic chromonic liquid crystals in periodically arranged micrometer scale air pillars. The anisotropic fluid arranges into chiral domains that depend on the arrangement and spacing of the pillars. We characterize the resulting domains by polarized optical microscopy, support their reconstruction by numerical calculations, and extend the findings with experiments, which include chiral dopants. Well-controlled and addressed chiral structures will be useful in potential applications like programmable scaffolds for living liquid crystals and as sensors for detecting chirality at the molecular level. Ključne besede: physical chemistry, atmospheric chemistry, chromatography, deformation, silicon, symmetry breaking, chiral domains, liquid crystal Objavljeno v DKUM: 03.04.2025; Ogledov: 0; Prenosov: 1
Celotno besedilo (11,64 MB) Gradivo ima več datotek! Več... |
2. A review of analytical techniques for the determination of e-liquid and electronic cigarette aerosol compositionMatjaž Rantaša, David Majer, Matjaž Finšgar, 2025, pregledni znanstveni članek Opis: Since the introduction of electronic cigarettes (ECs) to the global market, the composition of e-liquids has been a controversial topic. While some consider ECs to be an effective tool for quitting smoking, their primary criticism lies in the uncertain and varied composition of e-liquids. Manufacturers create the desired formulations by mixing different ratios of humectants, flavorings, nicotine, cannabinoids, and cooling agents. However, the health effects of inhaling these compounds are still not well understood. Regular analytical control of e-liquids and aerosols is crucial to gain valuable insights into e-liquid composition, generating new compounds during aerosolization, and the potential impact on human health. This work presents an overview of the analytical techniques used for the qualitative and quantitative determination of e-liquid and aerosol compounds, including a description of the methods used for aerosol collection. Gas and liquid chromatography are the most used analytical techniques for compound determination, followed by nuclear magnetic resonance spectroscopy. Additionally, inductively coupled plasma-mass spectrometry and inductively coupled plasma-optical emission spectroscopy are the most frequently used analytical techniques for elemental determination in e-liquids and their aerosols. Ključne besede: electronic cigarettes, e-liquids, aerosol, gas chromatography, high-performance liquid chromatography, inductively coupled plasma mass spectrometry Objavljeno v DKUM: 21.03.2025; Ogledov: 0; Prenosov: 2
Celotno besedilo (2,11 MB) |
3. |
4. |
5. Resveratrol food supplement products and the challenges of accurate label information to ensure food safety for consumersMaja Bensa, Irena Vovk, Vesna Glavnik, 2023, izvirni znanstveni članek Opis: The food supplement market is growing as many consumers wish to complement their nutrient intake. Despite all the regulations in place to ensure food supplements safety, there are still many cases of irregularities reported especially connected to internet sales. Twenty resveratrol food supplement products sold on the Slovenian market were evaluated on their compliance of declared vs. determined resveratrol content, as well as the compliance of labels with the European Union (EU) and Slovenian regulatory requirements. Both the ingredient contents and food information are important parts of food safety. Analyses of 20 food supplements performed using high-performance thin-layer chromatography (HPTLC) coupled with densitometry showed that 95% of products had contents different from what was declared and 55% of products contained higher contents than declared. In 25% of the products the determined content per unit exceeded the maximum level (150 mg/day) specified in EU novel food conditions for food supplement with trans-resveratrol. Evaluation of the 20 food supplement labels included mandatory and voluntary food information, food supplement information, novel food information, health claims and nutrition claims. Most labels contained the necessary information, but multiple errors were observed ranging from typos to misleading practices. From a food safety perspective there is still a lot of improvement needed in the field of food supplements. Ključne besede: trans-resveratrol, dietary supplements, food safety, regulation, labels, health claims, nutrition claims, novel foods, high-performance thin-layer chromatography, HPTLC Objavljeno v DKUM: 15.04.2024; Ogledov: 199; Prenosov: 15
Celotno besedilo (4,06 MB) Gradivo ima več datotek! Več... |
6. |
7. A comparison of analytical techniques for the determination and monitoring of charge variants in therapeutic proteins : master's thesisEva Kropušek, 2023, magistrsko delo Opis: Charge variants of therapeutic proteins are considered to be drug product variants and process-related impurities. To monitor charge heterogeneity, the development of a new analytical method is needed. Imaged capillary isoelectric focusing, capillary zone electrophoresis, and cation exchange chromatography assays were evaluated as candidate assays to support the early development of two new biological drug candidates. These are the analytical techniques most frequently used in the pharmaceutical industry for monitoring charge heterogeneity. We compared the advantages and disadvantages of these analytical techniques for monitoring charge variants in two innovative monoclonal antibodies. The results obtained revealed similarities and differences in the various analytical techniques. However, there is only a short time-frame dedicated to analytical method development when developing new biological drugs. With this in mind, imaged capillary isoelectric focusing showed a perfect balance between the quality and speed of analysis. Ključne besede: Imaged capillary isoelectric focusing, capillary zone electrophoresis, cation exchange chromatography, charge variants, biological drug Objavljeno v DKUM: 03.10.2023; Ogledov: 638; Prenosov: 43
Celotno besedilo (3,02 MB) |
8. Simultaneous GC-MS determination of free and bound phenolic acids in Slovenian red wines and chemometric characterizationMilena Ivanović, Maša Islamčević Razboršek, Mitja Kolar, 2016, izvirni znanstveni članek Opis: Several phenolic acids (PAs), caffeic, vanillic, syringic, p-coumaric and ferulic acid, found in Slovenian red wines were studied using gas chromatography and mass spectrometry (GC-MS). For isolation of the PAs from wine samples, solid phase extraction (SPE) using hydrophilic modified styrene - HLB cartridges was used. The bound PAs were extracted after basic hydrolysis and o-coumaric acid was used as the internal standard (ISTD). The method developed was validated and the linear concentration range for all analytes was from 1 to 100 mg L$^{-1}$ with correlation coefficients above 0.999. We show that the method is repeatable (RSD<2%), recoveries were above 96%, and LOD and LOQ values were acceptable.
In all of the wine samples tested, caffeic and p-coumaric acid were determined to be the predominant PAs (17-72 mg L$^{-1}$), while other compounds were found in lower concentrations. Principal Component Analysis (PCA) and Cluster Analysis (CLU) were used to study differences between wines related towards varieties and Slovenian wine regions. The results demonstrate that variety has more influence on PAs content than wine regions in Slovenian red wines. Ključne besede: phenolic acids, Slovenian red wines, gas chromatography, mass spectrometry, PCA, CLU Objavljeno v DKUM: 25.08.2017; Ogledov: 2231; Prenosov: 388
Celotno besedilo (222,27 KB) Gradivo ima več datotek! Več... |
9. Determination of topiramate in human plasma using liquid chromatography tandem mass spectrometryTanja Vnučec, Lea Cvitkovič-Maričič, Helena Prosen, Darinka Brodnjak-Vončina, 2013, izvirni znanstveni članek Opis: The LC-MS/MS method for determination of the anti-epileptic drug topiramate (TPM) in human plasma was developed and validated for pharmacokinetic and bioequivalence study purposes. For quantitative determination of TPM values the method with deuterated internal standard (topiramate-d12) and liquid chromatography with tandem mass spectrometry was used. TPM was extracted from the human plasma using the solid-phase extraction procedure on a Strata X extraction column. Negative ions were monitored in the selected reaction monitoring mode (SRM) and transitions m/z 338.2 > 78.2 and m/z 350.3 > 78.2 were used for the quantitative evaluation of TPM and the internal standard, respectively. The results obtained from validation were statistically evaluated according to the requirements of European Medicines Agency (EMA) and Food and Drug Administration (FDA) regulatory guidelines. The linearity of the method was checked within a concentration range from 10 to 2000 ng/mL. Successful validation confirmed that this method is precise, accurate, sensitive and therefore suitable for determination of topiramate plasma levels in pharmacokinetic and bioequivalence studies. Ključne besede: topiramate, liquid chromatography tandem mass spectroscopy, human plasma, bioequivalence study Objavljeno v DKUM: 18.08.2017; Ogledov: 1609; Prenosov: 103
Celotno besedilo (189,19 KB) Gradivo ima več datotek! Več... |
10. Determination of candesartan in human plasma with liquid chromatography - tandem mass spectrometryVanja Forjan, Lea Cvitkovič-Maričič, Helena Prosen, Darinka Brodnjak-Vončina, 2016, izvirni znanstveni članek Opis: A sensitive, specific and rapid liquid chromatography - tandem mass spectrometry method was developed and validated for the determination of candesartan in human plasma. Analyte was separated from endogenous components present in plasma by solid phase extraction. Chromatographic separation was performed on Gemini C18 analytical column using mobile phase acetonitrile – 5 mM ammonium formate pH 2 (90:10, v/v) at flow rate of 0.3 mL/min. For detection, tandem mass spectrometry in SRM mode with positive electrospray ionization was used. The mass transitions m/z 441.1 > 263.1 and 445.1 > 267.1 were used to determine candesartan by using candesartan-d4 as an internal standard. After development, the method was validated according to the requirements of EMA regulatory guidelines in the concentration range 1 - 400 ng/ml in human plasma. Limit of quantification (LLOQ) was 1 ng/ml. The developed and validated method proved to be very fast and reproducible and was therefore successfully implemented in pharmacokinetic and bioequivalence studies with large number of study samples. Ključne besede: candesartan, liquid chromatography, tandem mass spectrometry, human plasma Objavljeno v DKUM: 17.08.2017; Ogledov: 1548; Prenosov: 391
Celotno besedilo (215,54 KB) Gradivo ima več datotek! Več... |