Kazimierz Wrobel

A new series of bis-2,5-aryl-1,3,4-oxadiazoles attached to bis-1,2,3-triazoles (4a-4i) was chemically upcycled from precursors obtained from the aminolysis of polyethylene terephthalate (PET) waste. This important progress in the functionalization of 1,2,3-triazoles was achieved by the very efficient copper-catalyzed azide-alkyne cycloaddition reaction (CuAAC). The resulting compounds were fully characterized by 1H and 13C NMR, mass spectrometry, and infrared spectroscopy. The present synthesis was obtained by sequential reactions; the initial reaction was chemical depolymerization of polyethylene terephthalate via aminolysis reaction using hydrazine as the amine component to obtain terephthalohydrazide (1) followed by upcycling to novel via cyclocondensation reaction with p-amino benzoic acid to obtain 4,4'-(1,4-phenylenebis(1,3,4-oxadiazole-5,2-diyl)) dianiline (2), which is further subjected to Sandmeyer reaction condition followed by nucleophilic aromatic substitution (SNAr) by sodium azide under aqueous medium to obtain 1,4-bis(5-(4-azidophenyl)-1,3,4-oxadiazol-2-yl)benzene (3) is crucial reactant for copper catalyzed azide alkyne reaction results the bis-2,5-aryl-1,3,4-oxadiazoles attached to bis-1,2,3-triazoles (4a-4i) in good to excellent yields.

The antioxidant properties of Se nanoparticles (SeNPs) have been frequently observed in biological systems. Reduced levels of hydrogen peroxide have been reported, but it remains unclear whether this effect is due to the increased activity of antioxidant enzymes caused by SeNPs or may be the result of their direct involvement in the reduction process. This work demonstrates the ability of SeNPs to reduce H ₂ O ₂ with concomitant oxidation of elemental Se to Se(VI) at physiological pH and in the presence of the major serum protein. SeNPs (96 ± 8 nm) were obtained from sodium selenite by addition of cysteine and bovine serum albumin. In a quantitative approach nanoparticles were added to the solution of hydrogen peroxide (5:1 molar excess of H ₂ O ₂ ) or to a solution where peroxide was continuously generated in the glucose–glucose oxidase system. During the reaction time of 60 min, oxidatively dissolved selenium and H ₂ O ₂ were determined by hydride generation‐microwave plasma‐atomic emission spectrometry and by UV–vis spectrophotometric assay, respectively. The results obtained indicate the conversion of SeNPs to Se(VI) in both systems. Within one hour, 5.9% of initial H ₂ O ₂ concentration was removed and when peroxide was enzymatically generated from glucose, its expected content was decreased by 17.2%.

The role of glyoxylic acid (GA) as a potential precursor of N^ε-carboxymethyl lysine (CML) at physiological pH was studied. A plausible reaction mechanism is proposed.

Tanned leather needs to be protected against microorganisms which is why various biocides are currently used. To evaluate the effectiveness of leather treatment and to control the concentrations of potentially harmful compounds, simple and reliable analytical procedures are required. In this work, two such procedures are proposed for the determination of eight fungicides in leather, consisting of acetonitrile extraction and liquid chromatography with electrospray ionization – mass spectrometry or diode array spectrophotometric detection (HPLC-ESI-ITMS and HPLC-DAD, respectively). According to the elution order, the analyzed compounds were: 2-bromo-2-nitropropane-1,3-diol (BNPD), methyl 1H-benzimidazol-2-yl-carbamate (CBZ), 2-mercaptobenzothiazole (MBT), 4-chloro-3-methylphenol (PCMC), 2-phenylphenol (OPP), 2-(thiocyanomethylthio)-benzothiazole (TCMTB), 2-n-octyl-4-isothiazolin-3-one (OIT), 1-[[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl]methyl]-1,2,4-triazole (PRO) and 2,5-diphenyloxazole (PPO) as an internal standard. For accuracy testing, three-point standard addition was performed with the percentage recoveries in the ranges 75.0–115% and 91.9–117% for HPLC-ESI-ITMS and HPLC-DAD, respectively. The chemical composition of acetonitrile leather extract had a minor effect on the IS-normalized signal magnitude within the calibration range of each fungicide, as demonstrated by signal suppression/enhancement factors of 84.1–112% and 93.6–102%. The detection power of HPLC-ESI-ITMS was better for all compounds compared to that of HPLC-DAD; however, in real-world samples both procedures consistently detected and quantified individual fungicides. The averaged quantification difference between the two procedures was evaluated yielding σ_N% values in the range 7.28–16.4%. It is concluded that the two procedures can be used interchangeably for the quantification of eight fungicides declared for use in the leather industry and that PPO is suitable as an internal standard in both.

Rollover iridacycle were easily obtained via a C–H bond activation on the remote position of the 2-(6-bromopyridin-2-yl)imidazo[1,2- a ]pyridine ligand. DFT calculations suggest that C–H bond activation occurs during the complexation of the second ligand.

The feasibility of raw data acquired by liquid chromatography – high resolution mass spectrometry for the separation of four tequila corresponding to different maturation stages was demonstrated using partial least squares regression (PLS). Five samples of silver, rested, aged, and extra-aged tequilas from different manufacturers were analyzed each in two technical replicates. Prior to the analysis, the samples were four-fold diluted with 0.1% trifluoroacetic acid. Rectangle bucketing was performed for raw data, with a retention time width of 60 s and m/z width of 1. The prepared dataset was submitted to principal component analysis (PCA) which allowed for the detection of tequila contaminants identified to be N-lauryl diethanolamine and phthalate esters. Next, PLS was performed on depurated data, annotating tequila categories as follows: 0 - silver, 1 - rested, 2 - aged and 3 - extra aged. In the computed model, two principal components accounted for 64% and 98% of X-data and Y-data variability, respectively. Cross-validation revealed similar analytical performance in calibration and in prediction with root mean square errors of 0.1851 and 0.2082, respectively. The assignation of category’s numerical value (0-3) was attained for eight randomly selected tequilas (two per category). Statistical differences between predicted values were obtained for each pair of categories except for the aged versus extra-aged liquors (ANOVA, p < 0.05). Overall, the assignation of tequila category was achieved with no need for the detection/identification nor quantification of individual compounds.