Journal of Analytical Chemistry最新文献

The sorption of ion associates of acidic azo dyes, sulfonazo and Congo red, with Dimedrol on polyurethane foams is studied depending on pH, phase contact time, and component ratio. A method for determining Dimedrol in medicinal products is developed based on its sorption as ion associates with dyes and subsequent detection on the sorbent surface by diffuse reflectance spectroscopy.

The chromatographic retention of neutral polar compounds (alcohols, ketones, carboxylic acids, carbohydrates, and sweeteners) and compounds in the ionized form (mono- and dibasic organic acids) on cation exchange columns packed with sulfonated poly(styrene-divinylbenzene) having crosslinking degrees of 8% (Nautilus-IE) and 10% (Sevko AA) is studied in ion exclusion chromatography. Using 5 mM sulfuric acid, the retention parameters of the compounds are determined and new patterns are obtained, clarifying the mechanism of retention of organic acids in ion-exclusion chromatography. It is found that the retention of all the studied compounds (logk') is directly proportional to hydrophobicity values (log P_exp). In this case, the electrostatic repulsion of organic acids from the sulfo groups of the cation exchanger shifts the log k'–log P_exp dependences by a constant value, proportional to the number of carboxyl groups. A possibility of using the Sevko AA column not only for amino acid analysis, but also for the determination of organic acids and alcohols in complex samples by ion exclusion chromatography with spectrophotometric and refractometric detection is shown.

Coatings for the inner walls of quartz capillaries were obtained using cationic high-molecular-weight chitosan with a degree of deacetylation of 95%. The dependence of the electroosmotic flow velocity on the pH of the background electrolyte was studied and the stability of the coatings under the influence of various solvents was assessed. The results were compared with those for another cationic coating based on poly(diallyldimethylammonium chloride) (PDADMAC). In separating amino acids, catecholamines, and organic acids, the chitosan-based coatings showed slightly lower efficiency compared to PDADMAC coatings, but provided higher resolution for the biologically active analytes studied. Chitosan on the inner walls of the quartz capillary enhanced enantioselectivity in the separation of enantiomers of β-blockers (carvedilol, propranolol, and sotalol) in the presence of (2-hydroxypropyl)-β-cyclodextrin in the background electrolyte, as well as nonsteroidal anti-inflammatory substances (ketoprofen and ketorolac) using vancomycin as a second chiral selector.

The study demonstrates that the interaction of dopamine with fluorescamine can serve as a basis for a fluorescence assay for dopamine using a camera, as the product formed in this interaction exhibits a fluorescence peak in the visible spectral region (485 nm). Fluorescence can be excited with a light-emitting diode emitting in the near-ultraviolet spectral region (395 nm). The reaction should be carried out at pH 8–8.5 in a phosphate buffer solution for 5 min, with fluorescamine being added to the reaction mixture last. The performance characteristics of the camera-based assay were evaluated and compared with those of a similar dopamine assay using a professional spectrofluorometer and a spectrophotometer. The limits of detection for dopamine using a camera, a spectrophotometer, and a spectrofluorometer were 1.8, 1.6, and 0.5 µM, respectively, while the analytical ranges were 5.4–50, 4.8–100, and 1.5–100 µM. The presence of common inorganic ions in concentrations 10 times higher than that of dopamine does not interfere with the assay. The proposed method for dopamine determination can be used for the quality control of pharmaceutical products.

A method is developed for immobilizing a binary gold–palladium (Au–Pd) system on the surface of a glassy carbon (GC) electrode coated with reduced graphene oxide (rGO). Using rGO as a matrix for the inclusion of the Au–Pd binary system significantly enhanced its catalytic activity for the electrooxidation of tetracycline. This improvement is attributed to an increased dispersity of the deposit and the formation of metal nanoparticles in the nanometer range, with an average particle size of 50 nm. The optimal conditions for immobilizing the Au–Pd binary system were identified to maximize the electrocatalytic effect. The feasibility of the amperometric detection of tetracycline on the GC electrode modified with the Au–Pd and rGO composite was demonstrated under flow-injection analysis conditions. The proposed method exhibits high sensitivity (with a detection limit of 5 nM), rapidity, and high throughput (60 samples/h). The developed flow-injection amperometric method for tetracycline determination was successfully applied to analyze flower honey samples from different regions of the Volga area.

A procedure is proposed for separating trace amounts of gallium from the macrocomponents Cr, Mo, W, Ni, and Co to determine gallium using inductively coupled plasma atomic emission spectroscopy in alloys based on nickel and iron (precision nickel alloys, alloyed and high-alloyed steel). Sodium fluoride was used as a precipitant. Optimal conditions for the coprecipitation of gallium on the precipitate during separation from the considered macrocomponents were determined. The limit of detection for gallium in separation from the macro quantities of Cr, Mo, W, Ni, and Co was 5 × 10^–4 wt %.

A new approach has been proposed to determining dibenzothiophenes in diesel fuels by HPLC-MS/MS with electrospray ionization. The developed method is based on the preliminary derivatization of the target compounds through their interaction with aliphatic alcohols in the presence of trifluoromethanesulfonic acid, resulting in the formation of fixed-charge derivatives. These derivatives undergo predictable fragmentation processes, involving the elimination of an alkene from the resulting cation, which allows for their detection by selected reaction monitoring. It has been demonstrated that this analytical method provides low limits of detection for the target compounds, making it suitable for analyzing fuels meeting Euro 5 standards.

Amphibian skin secretion provides the primary defense for frogs against various threats, including predators and pathogens. The composition of this secretion, which is rich in peptides, is unique to each amphibian species and may serve as a taxonomic biomarker, not only for frog species but also for their populations. In this study, we sequenced the components of the skin peptidome of frogs from the Novosibirsk population of Rana arvalis using a range of tandem mass spectrometry techniques, including CID, HCD, ETD, and EThcD. For the first time, we applied an alternative method for collecting secretion in field conditions, which involved manual stimulation to release the secretion. We also evaluated the applicability of the Novor.Cloud program for automatic peptide sequencing in Ranid frogs, focusing on the Novosibirsk population of R. arvalis. The skin peptidomes of the Novosibirsk, Moscow, and Central Slovenian populations of moor frogs were compared. Brevinin 1AVa, brevinin 1AVb, and the melittin-related peptide FQ-22-1, found in the skin secretion of all three populations, may serve as biomarkers for the moor frog, Rana arvalis.

The isotopic composition of pedogenic carbonates offers valuable insights into the paleoenvironments in which they formed. However, the analysis of these carbonates is complicated by the simultaneous presence of soil organic matter (SOM) alongside inorganic carbon (IC), the removal of which is a labor-intensive process. Previous research into the influence of organic matter on the isotope analysis of carbonates has yielded contradictory results, and some authors attributed the discrepancies to the properties and quantity of the organic matter. Some researchers suggested that sample preparation methods—such as thermal treatment, plasma ashing, the use of chemical reagents to remove organic matter, and the digestion of samples with phosphoric acid—affect the resulting δ¹³C and δ¹⁸O values more than the organic matter itself. There is no consensus about the necessity of removing SOM before the isotope analysis of carbonates. To assess the impact of SOM on the results of the isotope analysis of carbonates from peat soils, we conducted a series of experiments aimed to select the optimal sample preparation procedure for analysis by continuous-flow isotope ratio mass spectrometry. The study involved two horizons of Sapric Drainic Histosol the histic horizon (TE₂), with 41.67% soil organic carbon (SOC) content and a lower degree of decomposition, and the organogenic horizon (TT), with 4.45% SOC content and a higher degree of decomposition. For the δ¹³C analysis, the best results, comparable to those obtained by removing organic matter with H₂O₂, were achieved using 105% H₃PO₄ to decompose air-dried samples from the TT horizon, with an IC/SOC ratio up to 1 : 10. However, applying this approach to samples with an IC/SOC ratio of 1 : 20, or to soil from the TE₂ horizon with a higher SOC content and lower degree of decomposition, led to a significant depletion of ¹³C in the resulting CO₂. The use of 98% H₃PO₄, thermal treatment of samples at 90°C, and substantial reductions in equilibration time also caused deviations in the δ¹³C values towards a lighter isotopic composition. Deviations from the true values of δ¹⁸O were observed in all experiments. The best results were obtained when samples were digested with 105% H₃PO₄ without thermal treatment or the use of chemical reagents, regardless of the initial SOC content or the IC/SOC ratio.