Chemické listy

Essay on Nobel Prizes

Václav Pačes — 2024-12-15

Commercial

2024-12-15

Commercial

2024-12-15

Issue Contents & Masthead

2024-12-15

Volume Contents 118 (2024)

2024-12-15

Author Index 118 (2024)

2024-12-15

Volume Identifiers 118 (2024)

2024-12-15

Persistent Organic Pollutants PFAS: Challenges, Impacts and Legislative Measures

Lenka McGachy — 2024-12-15

In February 2023, the European Chemicals Agency (ECHA) announced that it has an expected detailed proposal for the restriction of more than 10,000 per- and polyfluoroalkyl substances (PFAS) under the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Regulation. The national authorities of Denmark, Germany, the Netherlands, Norway and Sweden submitted the proposal after identifying risks in the production, marketing and use of PFAS. In their view, the substances are not sufficiently controlled and need to be addressed at EU level. This article focuses on the implications of the proposed restriction of PFAS for consumers and markets, analysing the possible impacts on industry and everyday life. It also discusses the occurrence of PFAS in the environment and the impact of these persistent compounds on human health and the environment.

Enzymatic Synthesis and Its Use in Cladribine Production

Zdeňka Čížková — 2024-12-15

Enzymatic synthesis is an alternative to chemical synthesis and provides new possibilities in the preparation of pharmaceutically active substances. The aim is to minimize the inefficiency of the chemical method of preparation and increase its effectiveness. Despite advances, biotechnological processes in nucleoside synthesis using catalysis by nucleoside phosphorylases are not actively applied industrially. The development of an enzymatic synthesis route could bring benefits in terms of improved efficiency, process simplicity, and minimization of organic solvent consumption and thus environmental impact. The use of enzymatic synthesis in the production of cladribine provides a simple and rapid way of producing this active substance in high purity without the formation of undesirable by-products.

Useful Synthetic Polymer of N-vinylpyrrolidone, Its Properties and Applications

Jiří Michálek — 2024-12-15

This contribution summarizes the present-state of knowledge on vinylpyrrolidone, its (co)polymers, crosslinked structures based on it, and offers a rich survey of various applications, with a special focus on (bio)medicine. A brief history of this material is also given. Methods of preparation and technical parameters of both vinylpyrrolidone monomer and its various polymers are described. Important data are presented in tables.

Polymeric Nanofibers and Microfibers: New Formats of Materials Used in Chromatography for Sample Preparation Using Solid Phase Extraction

František Švec — 2024-12-15

For traditional sample preparation by solid phase extraction prior to HPLC separation, plastic or metal pre-columns filled with sorbent particles or, more recently, monolithic columns are commonly used. To a much lesser extent, fibrous sorbents are used for this purpose. This article aims at introducing the reader to the possibilities offered by fibrous sorbents in the field of analytical chemistry. Methods for the production of nanofibers and microfibers using electrospinning, meltblown, and their combination are described. These are also presented with a brief look at the history of their development. Examples of the polymers which the fibers are prepared from and their characteristics, which must be considered when selecting the polymer for extraction of the desired analytes, are also listed. Finally, some examples of extraction of substances presented in our publications are described, with a particular focus on samples that are complex in nature, such as the environmental and biological samples.

Migration of Micro-, Macroelements and Heavy Metals in the Trophic Chain of Bees

Nicolae G. Eremia — 2024-12-15

This study investigates the migration of microelements (iron, zinc, copper, manganese), macroelements (calcium, potassium, magnesium, sodium, phosphates) and heavy metals (cadmium, lead, nickel, chromium) through the trophic chain from soil to honey plants, bees, and their products (honey, propolis) across various soil-climatic zones of the Republic of Moldova over 2020–2023, employing standardized analytical methods. The findings highlight selective migration and bioaccumulation patterns, which are crucial for understanding element distribution in ecosystems.

Full text English translation is available in the on-line version.

Possibilities of Using a Virtual Source Model to Refine the Prediction of the Impact of Injurious Effects in Massive Releases of Toxic Gases

Jakub Marek — 2024-12-15

Massive leaks of toxic substances occur not only during accidents connected with the operation of industrial enterprises, but also during their transfers by the means of transport. These events pose a serious threat to both people and the environment. Particularly dangerous are situations where dense gas clouds are formed after the release of the given substance. These spread very quickly, while they tend to remain at the earth's surface for a relatively long time and flow into various depressions. In a few minutes, the toxic gas can reach a large area, as confirmed by the conclusions from the Jack Rabbit field tests. Knowledge of the behavior of heavy gas, as well as knowledge of events influencing its dispersion in real conditions, thus provide important information needed for effective management of the resulting accident. The key data is the extent of the harmful effects of the given hazardous substance, which can be obtained by simulating the predicted emergency situation using modeling software (e.g. ALOHA). However, the fundamental shortcoming of this approach is that these software usually generate overestimated results. The fact that dangerous concentrations in the real environment do not reach such distances from the source of leakage has been repeatedly proven by past accidents. The reason for this discrepancy is that the computer programs used do not allow to model with sufficient accuracy all the simultaneous physico-chemical processes that are applied during the dispersion of dense gas clouds. This task is far too complicated and only a part of it can be solved with the necessary precision. However, for the needs of emergency planning, these inaccuracies represent a relatively fundamental limitation. One way how to deal with this problem is to use a virtual resource (sometimes called a virtual point) model. It is successfully used in various areas where it is necessary to simplify the otherwise demanding physical modeling of the temporal and spatial distribution of matter emitted from a surface or volume source. The main idea of a virtual source is that the real primary emission source is approximated to an imaginary source that is located at a different location but acts and appears outwardly as if it were a real source of leakage. The key task of this solution is to determine the parameters of this source, because this is the only way to obtain results with significantly higher reliability during the subsequent simulation of the considered accident scenario.

Chemické listy

Essay on Nobel Prizes

Commercial

Commercial

Issue Contents & Masthead

Volume Contents 118 (2024)

Author Index 118 (2024)

Volume Identifiers 118 (2024)

Advertisement

Advertisement

Persistent Organic Pollutants PFAS: Challenges, Impacts and Legislative Measures

Enzymatic Synthesis and Its Use in Cladribine Production

Useful Synthetic Polymer of N-vinylpyrrolidone, Its Properties and Applications

Polymeric Nanofibers and Microfibers: New Formats of Materials Used in Chromatography for Sample Preparation Using Solid Phase Extraction

Migration of Micro-, Macroelements and Heavy Metals in the Trophic Chain of Bees

Possibilities of Using a Virtual Source Model to Refine the Prediction of the Impact of Injurious Effects in Massive Releases of Toxic Gases