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Macrolides are a group of compounds used to treat bacterial infections in humans and animals. Their widespread use results in the contamination of the water environment, which, on the one hand, has a detrimental effect on aquatic organisms and, on the other hand, can lead to the emergence of resistant strains of microorganisms. All of the above determines the need for monitoring of these compounds in the environment, particularly, in water objects. Usually, the high‐performance liquid chromatography combined with tandem mass spectrometry method is used to solve this problem, however, this work shows the possibility of using the supercritical fluid chromatography‐tandem mass spectrometry method. An approach for the determination of four common macrolides, namely erythromycin, clarithromycin, midecamycin, and josamycin, was developed. The use of solid‐phase extraction allowed to achieve limits of quantification at 0.57–6.8 ng/L. The presented approach was validated and tested on a real object—a sample of municipal wastewater. [ABSTRACT FROM AUTHOR]

This article discusses the use of lignocellulose, a renewable source of chemical products, for the production of high-value compounds. The authors focus on the nitration of lignin-derived monomeric products, such as vanillin, to produce 5-nitrovanillin. They explore the use of acetyl nitrate as a nitrating agent and highlight its advantages over other methods. The study demonstrates that the nitration of vanillin is highly selective and can be carried out in a simple and efficient manner. The authors hope that this research will contribute to the practical applications of lignin-derived structures and enhance our understanding of their reactivities. [Extracted from the article]

Unsymmetrical dimethylhydrazine (UDMH) based rocket fuel, when released into the soil, undergoes oxidative transformations to form a variety of toxic nitrogen‐containing products (TPs). Loamy soils containing aluminosilicates (clay) are capable of strong binding and retention of UDMH TPs due to a combination of polar sorption and cation‐exchange properties, posing challenges for their extraction and quantification. To overcome this problem, the present study proposes direct thermal desorption (TD) of analytes from loam facilitated by the addition of modifiers competing with UDMH TPs for sorption centers and ensuring their conversion into molecular form. Among tested additives, the mixture of potassium chloride and hydroxide demonstrated the best performance and provided recoveries of the most UDMH TPs exceeding 70% under optimized TD conditions (200°C, 30 min). The online combination of TD with gas chromatography‐tandem mass spectrometry allowed for the development of a method for the determination of 15 UDMH TPs in loamy soils with limits of detection in the range of 0.2–15 µg/kg. The use of matrix‐matched calibration and deuterated internal standards ensured high accuracy (80%–100%) and precision (relative standard deviation < 18%) of the analysis. The developed method was validated and successfully tested in the analyses of real loamy soil samples polluted with rocket fuel. [ABSTRACT FROM AUTHOR]

Water treatment for most public pools involves disinfection with active chlorine leading to the formation of disinfection by-products (DBPs). Among them, nitrogen-containing compounds (N-DBPs) having increased toxicity and adverse effects on human health are of the greatest concern. Being the major component of various body washers for swimmers, cocamidopropyl betaine (CAPB) represents a potential and still underestimated anthropogenic precursor of N-DBPs in pool water. The purpose of this study was to investigate CAPB transformation pathways and mechanisms under the aqueous chlorination conditions. High-performance liquid and two-dimensional gas chromatography hyphenated with high-resolution mass spectrometry were used for the search and tentative identification of the primary and final CAPB transformation products. A wide range of DBPs containing up to five chlorine atoms including these in combination with hydroxyl and additional carbonyl groups has been revealed in model chlorination experiments for the first time. The proposed mechanism of their formation involves nucleophilic substitution of the secondary amide hydrogen atom at the first stage with subsequent free radical and electrophilic addition reactions resulting in non-selective introduction of halogen atoms and hydroxyl groups in the alkyl chain. The deep transformation products include short-chain chlorinated hydrocarbons and their oxidation products as well as dimethylcarbamoyl chloride possessing high toxicity and carcinogenic properties. Targeted analysis of real swimming pool water samples confirmed the results of model experiments enabling semi-quantitative determination of CAPB (0.8 µg L–1) and 18 primary DBPs, including 10 chlorine-containing compounds with the total concentration of 0.1 µg L–1. Among them, monochloro (50%) and hydroxydichloro (25%) derivatives predominate. The toxicity and health of the main DBPs has been estimated using QSAR/QSTR approach. Thus, the possibility of formation of new classes of potentially toxic chlorine-containing DBPs associated with the widespread use of detergents and cosmetics was shown. [ABSTRACT FROM AUTHOR]

Lignans constitute a large group of phenolic plant secondary metabolites possessing high bioactivity. Their accurate determination in plant extracts with a complex chemical composition is challenging and requires advanced separation techniques. In the present study, a new approach to the determination of lignans in coniferous knotwood extracts as the promising industrial-scale source of such compounds based on comprehensive two-dimensional liquid chromatography separation and UV spectrophotometric detection is proposed. First and second-dimension column screening showed that the best results can be obtained using a combination of non-polar and polar hydroxy group embedded octadecyl stationary phases with moderate (~40%) "orthogonality". The optimization of LC × LC separation conditions allowed for the development of a new method for the quantification of the five lignans (secoisolariciresinol, matairesinol, pinoresinol, 7-hydroxymatairesinol, and nortrachelogenin) in knotwood extracts with limits of quantification in the range of 0.27–0.95 mg L−1 and a linear concentration range covering at least two orders of magnitude. Testing the developed method on coniferous (larch, fir, spruce, and pine) knotwood extracts demonstrated the high selectivity of the analysis and the advantages of LC × LC in the separation and accurate quantification of the compounds co-eluting in one-dimensional HPLC. [ABSTRACT FROM AUTHOR]

Lignans are widespread polyphenolic secondary plant metabolites possessing high biological activity. One of the most promising industrial-scale sources of such compounds is coniferous knotwood, containing a large number of polyphenolic compounds. Their use in pharmaceutical and other industries is limited by the difficulty in obtaining high-purity preparations from plant material and the requirement of advanced separation techniques. In this study, supercritical fluid chromatography on polar stationary phases was proposed for the efficient separation and identification of spruce, pine, fir, and larch knotwood extractives. Among the six tested sorbents, the best results were shown by silica with grafted diol and 2-ethylpyridine groups under conditions of gradient elution with a carbon dioxide–methanol mobile phase, which ensured the efficient retention and separation of analytes due to donor–acceptor interactions. Scaling up the method on a DIOL stationary phase provided a semi-preparative separation of extractives within 30 min to obtain 14 individual compounds with a purity of 90–99% and yields from 0.3 to 51% of the dry extract. These included eight lignans (nortrachelogenin, matairesinol, oxomatairesinol, α-conidendrin, 5-hydroxymatairesinol and its isomer, lariciresinol, and secoisolariciresinol), two oligolignans, three stilbenes (pinosylvin and its methyl ester, pterostilbene), and flavonoid taxifolin. The developed approach is distinguished with low operational costs, low consumption of organic solvents, environmental safety, and it is fully consistent with the principles of green chemistry. [ABSTRACT FROM AUTHOR]

A knotwood of coniferous trees containing large amounts of polyphenolic extractives is considered a promising industrial-scale source of lignans possessing antioxidant properties and other bioactivities. The present study is aimed at a detailed characterization of the chemical composition and antioxidant activity of lignan-rich extractives obtained from the knotwood of the Norway spruce, Scotch pine, Siberian fir, and Siberian larch growing in the European North of Russia as a region with a highly developed forest industry. To achieve this, a comprehensive approach based on a combination of two-dimensional NMR spectroscopy with high-performance liquid chromatography—high-resolution Orbitrap mass spectrometry, and the determination of antioxidant activity by the three complementary methods were proposed. The studied knotwood samples contained from 3.9 to 17% of extractive substances and were comparable to Trolox's antioxidant activity in the single-electron transfer processes and superoxide radical scavenging, which is associated with the predominance of polyphenolic compounds. The latter was represented by 12 tentatively identified monolignans and 27 oligolignans containing 3–5 phenylpropane units in their structure. The extracts were characterized by an identical set of lignans and differed only in the ratios of their individual compounds. Other components of the knotwood were flavonoids taxifolin, quercetin (Siberian larch), and three stilbenes (pinosylvin, its methyl ester, and pterostilbene), which were identified in the Scotch pine extractives. Sesquiterpene juvabione and its derivatives were found in extracts of Siberian larch knotwood. [ABSTRACT FROM AUTHOR]