In recent years, human impact on the Earth’s ecological environment has become increasingly visible, with serious negative consequences. One of the most important pollutants are heavy metals which can easily bind to sediments. Due to their toxic behavior, persistence, lack of biodegradability and bioaccumulation, they are considered key river pollutants that need to be controlled. This study examined two rivers: the Liwiec and Muchawka rivers located in south-eastern Poland. The mouth of the Liwiec River is the Bug River, which is partly the border between Poland and Belarus. In turn, the mouth of the Muchawka River is the Liwiec River. The objectives of the study were the following: (1) To complete a qualitative analysis of heavy metals (Cd, Pb, Cu, Ni, Zn) in the waters and bottom sediments of the Liwiec and Muchawka rivers; (2) To assess the degree of heavy metal contamination; (3) To identify the sources of contamination. The analysis included samples of surface water and bottom sediments collected (16 water and 16 bottom sediment samples were taken from the Muchawka River and 32 water and 32 bottom sediment samples were taken from the Liwiec River) in June and September 2022. The variability of characteristics, such as temperature, precipitation and humidity, contributes to seasonal changes in the distribution characteristics and sources of heavy metals. The study showed that only a small part of the heavy metals entering rivers are present in the water depth in the dissolved state, and most of them enrich the sediment, resulting in much higher concentrations of heavy metals in the sediment than in the water column. The differences in the distribution of some elements in water and sediment are due to the fact that surface sediments retain long-term records. Therefore, sediment can be considered a potential source of heavy metals in the aquatic environment. In general, the content of heavy metals determined in bottom sediments was not high but indicative of anthropogenic human activity. There is a possibility of re-release of heavy metals from the sediment into the water when hydrodynamic conditions or environmental factors (pH, redox potential, etc.) change, which could lead to secondary water pollution. The data obtained will be of great importance to both researchers studying river systems and the population living in the area.

Stilbene and its derivatives belong to the group of biologically active compounds. Some derivatives occur naturally in various plant species, while others are obtained by synthesis. Resveratrol is one of the best-known stilbene derivatives. Many stilbene derivatives exhibit antimicrobial, antifungal or anticancer properties. A thorough understanding of the properties of this group of biologically active compounds, and the development of their analytics from various matrices, will allow for a wider range of applications. This information is particularly important in the era of increasing incidence of various diseases hitherto unknown, including COVID-19, which is still present in our population. The purpose of this study was to summarize information on the qualitative and quantitative analysis of stilbene derivatives, their biological activity, potential applications as preservatives, antiseptics and disinfectants, and stability analysis in various matrices. Optimal conditions for the analysis of the stilbene derivatives in question were developed using the isotachophoresis technique.

Due to their toxicity, lack of bioaccumulation and biodegradability, and ease of binding to sediments, heavy metals are considered the main pollutants of rivers. It is, therefore, necessary to control and monitor these pollutants. The present study analyzed the Krzna River, which flows in southeastern Poland and has an outlet to the Bug River. Over much of its length, the Bug River forms Poland’s border with Belarus, while its origin is in Ukraine. The main purpose of the conducted research was a qualitative and quantitative analysis of selected heavy metals, i.e., Ni, Pb, Zn, Cd, and Cu, in bottom sediments and surface waters of the Krzna River. The secondary objectives were to evaluate the level of contamination of the studied matrices and identify the sources of pollution. Eighty samples of water and bottom sediments from the Krzna River were collected for the analysis. Due to the varying distribution of metals under the influence of changes in temperature, precipitation, and humidity, the samples were collected in May and August 2023. The average cadmium content in the sediments studied was the same in both May and August, at 0.6 mg/kg. In contrast, the nickel content of the sediments ranged from 4.6 to 6.1 mg/kg in May and from 4.8 to 6.8 in August. Only nickel and cadmium of the five heavy metals tested were present in amounts exceeding the geochemical background value. Analysis of the results indicates that only a minimal amount of heavy metals remain dissolved in the surface waters, and the remainder contaminates the sediments. The average concentrations of metals in the studied bottom sediments and surface waters were as follows: zinc > lead > nickel > copper > cadmium. The content of metals in the studied sediments was not high, but at the same time, their presence above the geochemical background indicates anthropogenic human activity. Any changes in hydrodynamic conditions and various environmental factors may result in the re-release of heavy metals contained in sediments into surface waters.

The paper presents results of the research on the dynamics of changes in the concentration of mercury in surface waters. The importance of mercury as an environmental pollutant results from specific properties of this metal, many sources of contamination, volatility, mobility, stability and high toxicity of its specific chemical forms. Samples of surface water collected from three rivers: the Bug, the Liwiec and the Muchawka were analysed. The Muchawka River flows into the Liwiec River, which in turn is a tributary of the Bug River. The technique of isotachophoresis was employed, using a solution of a biodegradable and environmentally non-toxic derivative of electrostatically stabilised silanates as the terminating electrolyte. The highest average mercury concentration of 0.89 μg/dm³ was determined in water samples collected from the Bug River in January, whereas the lowest concentration of 0.42 μg/dm³ was recorded in water collected from the Muchawka River in September.

The paper presents optimum conditions for separation and determination of three dimethyl derivatives of ES-silanates by capillary isotachophoresis. The following were considered in the study: 1-[(N,N-dimethyl)aminiomethyl]-spirobi(1-sila-2,5-dioxacyclopentan-3-on)at, 1-[(N,N-dimethyl)aminiomethyl]-spirobi(1-sila-2,5-dioxa-4-methylcyclopentan-3-on)at, and 1-[(N,N-dimethyl)aminiomethyl]-spirobi(1-sila-2,5-dioxa-4,4-dimethylcyclopentan-3-on)at. An aqueous solution of 4,4'-bis{1-[(N,N-dimethyl)aminiomethyl]spirobi(1-sila-2,5-dioxacyclopentan-3-on)at} was proposed as a terminating electrolyte in the determination process. The optimum time of analysis did not exceed 7 min. The limit of identification of ES-silanates was 2.0 µg · L⁻¹ and the limit of quantification was 6.6 µg · L⁻¹. The newly developed method allows for a more extensive research on the biological activity of hypercoordinated compounds belonging to ES-silanates and increases their applicability (e.g., as terminating electrolytes). Graphical Abstract

Fully effective antimalarial drugs are yet to be isolated or synthesized, hence the search them continues. The study was aimed at establishing the most suitable conditions for the separation and determination of six biologically active alkaloids, quinoline derivatives, using high performance liquid chromatography with UV/Vis detection. The experiments involved the following derivatives: quinine, quinidine, cinchonine, cinchonidine, acetylcinchonine and acetylquinidine. Of the six stationary phases used, only the naphthylpropyl column enabled the separation of all alkaloids. The octadecyl column, considered by many analysts as a reference, did not provide successful separation. The naphthylpropyl column had also very good validation parameters, including a wide range of linearity, high values of correlation coefficients (0.9990‒0.9998) and low standard measurement uncertainty (1.8‒2.3 µg L^‒1). The newly developed method was employed to evaluate the content of quinine in tonic-like beverages. The naphthylpropyl stationary phase provided ≤5% repeatability of quinine determination. GRAPHICAL ABSTRACT