Chemotherapeutics are among the most frequently prescribed medications in modern medicine. They are widely prescribed; however, problems with organisms developing resistance to these drugs means that ...their efficacy may be lost, so care should be taken to avoid unnecessary prescription. It is therefore of great interest to study the detailed metabolism of these biologically active compounds. This study aimed at developing an efficient analytical protocol for the determination of in-vitro electrochemical products of selected antibiotic drugs (amoxicillin, cefotaxime, fluconazole, linezolid, metronidazole and moxifloxacin). Combination of electrochemistry (EC) and mass spectrometry (MS) was applied for the in-vitro determination of the studied antibiotics and their electrochemical products. To identify the structure of the detected electrochemical products, MS/MS experiments were performed. This was one of the first applications of the EC system for generation of electrochemical products produced from antibiotic drugs. Adjustment of appropriate conditions and such parameters as the potential value, mobile phase (pH), working electrode and temperature had significant influence on electrochemical simulations and the creation of selected derivatives. Consequently, several working electrodes were evaluated for this purpose. In most of the studied cases, mainly two types of products were observed. One corresponded to an increase in mass by 14Da, which can be explained by a process consisting of oxidation (+16 m/z) and dehydrogenation (−2 m/z); The second in turn showed mass reduction by 14Da, which can be attributed to the loss of -CH2 as a result of N-demethylation. The performed experiments consisted of two stages: electrochemical oxidation of the analyzed samples (phase I of metabolic transformation), and addition of glutathione (GSH) for follow-up reactions (phase II conjunction). The electrochemical results were compared to in-vivo experiments by analyzing urine samples from patients after antibiotic drugs have been administered.. Overall, the comparison of electrochemistry to in-vivo experiments shows the high potential of EC-MS as a fast analytical tool in the prediction of electrochemical conversion that could be applied to therapeutic drug monitoring and pharmacokinetic studies as well.
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•EC-MS was applied for generation of metabolites produced from antibiotic drugs.•EC-MS technique provides an analytical tool to simulate both phase I and phase II.•Comparison of EC-MS to in-vivo experiment shows potential of an analytical tool.
The vials used for the preparation of breath samples for automated solid-phase microextraction-gas chromatography-mass spectrometry analysis are crimped with septa. These septa often emit specific ...volatile organic compounds (VOCs) confounding the measurement results of breath samples. In the current paper, 14 different brands of magnetic caps with silicone-polytetrafluoroethylene (PTFE), butyl-PTFE, or butyl rubber septa were tested. The total emission of septa over a 4 h period was also evaluated. The tested septa emitted 39 different compounds, which are mainly hydrocarbons, alcohols, and ketones. Acetone and toluene are the most abundant out-gassing products. The concentration of acetone was in the range from 55 to 694 ppb for butyl-PTFE septum (brand 14) and butyl rubber (brand 10), respectively. The measured toluene amount was 69-1323 ppb for the septum brand 14 and brand 8 (silicone-PTFE), respectively. Generally, the butyl rubber septa released higher amounts of contaminants in comparison to the silicone ones.
Differences in the surface charges of bacteria can be exploited for their separation by capillary electrophoresis. Because of their low electrophoretic mobility, the separation is not always easy to ...perform, especially in the presence of the electroosmotic flow. Elimination of electroosmotic flow by capillary wall modification with γ‐(trimethoxysilyl)propyl methacrylate followed by acrylamide bonding permits separation over a distance of 8.5 cm.
The present research emphasizes the use of safe, inexpensive, and available whey using Lactobacillus paracasei as a source in silver nanocomposite synthesis as an alternative bioactive agent for ...dairy and biomedical applications. Through the multiinstrumental approach used in this study based on spectroscopic and microscopic methods as well as spectrometric techniques, the characterization and evaluation of silver composites and their antimicrobial and antiradical properties were enabled. Synthesized silver nanocomposites have been found in form of nanocrystals, naturally coated by an organic surface with high antimicrobial and antiradical properties. Furthermore, this work also presents an innovative approach regarding the organic surface (naturally secreted by the bacteria isolated from whey) of the core of nanoparticles, which has already been explored and therefore is starting to supplement the scientific approach concerning biologically synthesized nanoparticles. This work also presents a general frame on the resistance subject by performing the trial interaction of commercially available antibiotics (kanamycin and ampicillin) with new bioactive compounds that can create novel knowledge on complementing their action. Moreover, synthesized silver nanocomposites have shown great antioxidant and antimicrobial effects against various foodborne pathogens from dairy products and drug resistance pathogens found in the medical area to rank on the top of mortality rate.
A study was carried out on the sorption of the herbicide linuron in podzolic soil (one of the typical soils of Poland), the sorption isotherms being obtained using batch equilibrium studies. ...Modelling sorption phenomena involving the interactions of chemicals and particularly herbicides is very difficult because of the strong heterogeneity of the soil matrix. The present work presents the results of applying the most common models, i.e. Freundlich and Linear, as well as the newer concept of the Dual Reactive Domain model. The data obtained were validated using various statistical and chemometric methods.
The results suggest that applying the non-linear least-squares method to obtain isotherm parameters gave a much better description of the sorption phenomena than often obtained using linear transformations of the adsorption equations. The study also showed that appropriate weighting schemes should be included in any model calculations. To test the goodness-of-fit of the model to the experimental data both the correlation coefficient and the Residual Root Mean Square Error were obtained. The models were also compared using the Extra Sum of Squares Principle statistical test.
Combined effects of temperature and mobile phase on the reversed phase chromatographic behavior of alkylbenzenes and simple substituted benzenes were investigated on a Blaze C₈ polydentate ...silica-based column, showing improved resistance against hydrolytic breakdown at temperatures higher than 60°C, in comparison to silica-based stationary phases with single attachment sites. For better insight into the retention mechanism on polydentate columns, we determined the enthalpy and entropy of the transfer of the test compounds from the mobile to the stationary phase. The enthalpic contribution dominated the retention at 80% or lower concentrations of methanol in the mobile phase. Entropic effects are more significant in 90% methanol and in acetonitrile-water mobile phases. Anomalies in the effects of mobile phase on the enthalpy of retention of benzene, methylbenzene and polar benzene derivatives were observed, in comparison to regular change in enthalpy and entropy of adsorption with changing concentration of organic solvent and the alkyl length for higher alkylbenzenes. The temperature and the mobile phase effects on the retention are practically independent of each other and - to first approximation - can be described by a simple model equation, which can be used for optimization of separation conditions.
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