Journal of Analytical Chemistry最新文献

Singly charged background argide ions ArH⁺, ArN⁺, ArO⁺, and Ar²⁺ create strong spectral interferences in elemental and isotopic analysis by inductively coupled plasma mass spectrometry (ICP MS). In this study, we experimentally investigated the behavior of these ions depending on variations in high-frequency plasma power and argon carrier gas flow rate. Theoretical analysis was performed using thermodynamic modeling to predict the behavior of these argide ions on changes in plasma temperature and argon flow rate. Common patterns in the intensity of these major background ions and changes in their formation efficiency at different working parameters of the ICP are noted. A good agreement between the observed experimental dependences and those derived from thermodynamic models is noted.

This work was devoted to a study of the composition of protein concentrates from amaranth grain (Amaranthus hypochondriacus L.) of variety Voronezh. Amaranth protein concentrates were obtained by alkaline extraction of proteins and neutralization of the solution followed by ultrafiltration, by separating the starch fraction with amylolytic enzymes, and by alkaline extraction of proteins and their precipitation at pH 4.5. Conditions for the extraction of proteins followed by chromatography–mass spectrometric analysis and identification were selected. It was found that proteins from amaranth grain were more effectively extracted with a buffer with urea at protein concentrations of 1.7, 1.9, and 2.9 mg/cm³ in solution, respectively, while a buffer with detergents was more effective for the extraction of low-molecular-weight proteins at protein concentrations of 4.9, 2.9, and 9.0 mg/cm³ in solution, respectively. As a result of HPLC–MS/MS analysis followed by identification and search in the UNIPROT database, it was established that the main protein of amaranth grain is 11S-globulin, which acts as a reserve protein of amaranth seeds. In amaranth concentrates, 14 unique proteins belonging only to A. hipochondriacus L. were identified, and also proteins that did not belong to this species were reliably identified. Based on the results of semiquantitative analysis of the peptide profile of amaranth grain protein concentrates, a high frequency of occurrence of the main 11S-globulin proteins was established in all samples. The frequency of occurrence of other proteins in samples obtained by different methods differed significantly due to the peculiarities of protein isolation from amaranth grain. The results obtained can be used to prepare plant protein concentrates with a given protein composition.

In this brief review, we consider various characterizations of “monomeric” reversed phases for elucidating the interactions governing adsorbate retention in liquid chromatography. Conventional methods related to the assessment of retention capacity and hydrophobicity (specifically methylene selectivity) using single mobile phase compositions are discussed with a focus on dispersion interactions, along with their inherent strengths and limitations. An alternative approach involving separation maps through relative retention analysis is proposed. It is noted that, in real reversed-phase adsorbents, the density of the attached alkyl chains is typically one half of that of solid n-alkanes. In this case, adsorbate molecules to penetrate into the attached phase, and the process depends on the molecular shape. Consequently, conventional “monomeric” reversed phases exhibit specific selectivity towards substances with specific structures. The review also notes that current analytical methods often do not pay sufficient attention to the difference between the substance retention mechanisms, absorption and adsorption, because the predominant parameters of these mechanisms are quite different. Moreover, in the two most widely used very interesting and informative methods, linear solvation energy relationships (LSERs) and the hydrophobic-subtraction model, this characteristic has not received due attention. Taking into account that the method does not distinguish adsorbates retained by different mechanisms, absorptive versus adsorptive, to the obtained significant discrepancies between the calculated and experimental data do not seem extraordinary. The interpretation of the results of an LSER analysis is also complicated by uncertainties in the contributions of partial properties of adsorbates in both mobile and stationary phases to the total solvation energy, as only their difference is typically calculated. Nonetheless, a comparison of different columns in identical mobile phases can yield informative insights. A drawback of the second approach is the necessity of using multiple columns with substantial qualitative differences in the adsorbate retention among them. Furthermore, a possibility of the decomposition of all interactions into distinct types seems questionable, because the method does not involve any orthogonal (independent of the applied calculation method) properties.

The application of composite films consisting of crosslinked polyvinyl alcohol and magnetite as sensitive elements in the determination of the composition of aqueous solutions by digital colorimetry is described. A novel approach to fabricating composite materials of the composition hydrophilic polymer–magnetite is proposed; it involves the precipitation of Fe₃O₄ particles in ammonia vapors. The sensor films produced by this method were employed for determining the volume fraction of alcohol in products characterized by high alcohol content. The limit of detection for ethanol was determined at 63 vol %, while for isopropanol, it 24 vol %. The efficacy of the proposed sensor materials was assessed through in an analysis of liquid hand sanitizers.

The microelemental composition and isotope ratios Pb/U, Pb/Th, and Pb/Pb in apatite were determined by inductively coupled plasma and laser ablation mass spectrometry with on a NexION 300S spectrometer with an NWR 213 laser ablation (LA) attachment; the procedure for processing the experimental data was described. The optimal operation parameters of the mass spectrometer and the LA attachment were determined, also in determining the trace element composition and U/Pb dating from one crater of a size of 50 μm or more. In determining the microelemental composition of apatite, standard synthetic glasses NIST SRM-612, -610 were used; in measuring isotope ratios, reference samples (RS) were used—Durango, Mun Mad, and Mud Tank apatites, analyzed in laboratories in different countries. Using scanning electron microscopy data, the shape of laser ablation craters in RS apatite grains was analyzed; a significant heterogeneity of grains in the matrix and impurity elements was shown. The performance characteristics of the procedures for the measurement period 2021−2023 are presented. The repeatability of measuring the isotope ratios ²⁰⁶Pb/²³⁸U and ²⁰⁸Pb/²³²Th is 0.54 and 0.72, 7.5 and 14.3, 1.5 and 4.4% for Mun Mad, Durango, Mud Tank, respectively. Variations in the REE content of the reference samples (RSD) are 11−24, 5−13, 0.3−7% for Mun Mad, Durango, Mud Tank, respectively. The dating of the RS of apatite, within the limits of uncertainty, corresponds to those obtained in world laboratories. The methods were tested in the analysis of a number of apatite samples from Ural sites.

A rapid method is developed for the determination of bisphenol A (BPA) in ethanolic extracts by gas chromatography–mass spectrometry (GC–MS). The GC–MS method has acquired reference status in accredited analytical laboratories in identifying contaminant impurities in food and alcohol products. Bisphenol A is used as a monomer in the production of a number of plastics and epoxy resins; in its free form, it can be contained in quantities exceeding the permissible level in food containers. Bisphenol A can accumulate in a human body and cause harmful health effects. The studies were performed on an Agilent 8890 gas chromatograph equipped with a mass selective detector model 5977B and a 30 m long Ultra ALLOY^®-5 UA5-30M-0.25F capillary column. Optimal modes for the determination of bisphenol A in ethanolic extracts were selected. The direct determination of BPA in ethyl solutions without derivatization using GC–MS can be recommended for the development of procedures for monitoring the quality and safety of food packaging, monitoring BPA in alcohol-containing liquids, as well as in forensic medical examination as a reference procedure to confirm the reliability of BPA identification.

Effective solid-phase extractants (SPE) based on multi-walled carbon nanotubes (CNT) of various structures modified with an organic reagent, 2-mercaptobenzothiazole, were developed. Using scanning and transmission electron microscopy, the morphological and structural features of SPE samples and their elemental composition were determined. It was shown that the specific surface area of the modified CNT is approximately two times lower compared to the original CNT. It was revealed that the modified materials are CNT coils coated with a uniform organic shell 10−15 nm thick. The sorption capacity of the original nanotubes in 1.0 M HCl and of their modified forms (in 0.1−3.0 M HCl) at room temperature and at 80°C was determined. It was found out that in strongly acidic media, SPE based on G-183 CNT and 2-mercaptobenzothiazole, effectively sorbs Pt, Pd and Au at room temperature, and Ru and Rh at the temperature of 80°C. A possibility of the selective extraction of platinum group metals and gold with this sorbent in the presence of macroquantities of Al, Fe, Cu, Ca and Mg was assessed.

The aim of this work was to the obtaining novel mixed-mode stationary phases with increased hydrophilicity and applying them in ion and hydrophilic interaction liquid chromatography. The resins were obtained by the sequential covalent attachment of branched polyethylenimine and polyelectrolytes synthesized from diepoxide and a secondary amine on the surface of epoxidized polystyrene–divinylbenzene. To increase the shielding degree of the polymer substrate, an additional polymerization of glycidol was carried out in the functional layer of the sorbent at an increased pH of the reaction medium. The synthesized phases possessed increased hydrophilicity compared to most resins based on a styrene–divinylbenzene copolymer with covalently attached layers. This was evidenced in the ion chromatography mode by a decrease in the relative retention of polarizable anions, weakly hydrated oxyhalides (up to a change in the elution order of the bromate), and haloacetic acids. In the hydrophilic interaction liquid chromatography mode, an increased hydrophilicity of the phases was confirmed by an increase in the retention factors of polar analytes, as well as by the reversal of the elution order of ascorbic and nicotinic acids as compared to the phases based on polystyrene–divinylbenzene presented in the literature. The low efficiency of the obtained stationary phases in the ion chromatography mode was noted, which is associated with slow mass transfer in the bulk polymer functional layer. The negative impact of the polymer layer on efficiency in hydrophilic interaction liquid chromatography is less pronounced due to the presumably smaller thickness of the part of the functional layer involved in this mode. The proposed method for the synthesis of resins ensures an increase in the efficiency, selectivity, and separation ability of sorbents in the hydrophilic interaction liquid chromatography mode as compared to phases based on a styrene–divinylbenzene copolymer described previously in the literature. The resulting highly hydrophilic resins makes it possible to separate a mixture of 9 nitrogenous bases and nucleosides in 18 min, 6 vitamins in 24 min, and 8 sugars in 11 min. Thus, the method of substrate hydrophilization proposed in this work is promising for improving the chromatographic characteristics of phases in the hydrophilic interaction liquid chromatography mode and can be used to create sorbents with increased selectivity and efficiency.

In recent years, microRNAs have been used as cancer markers in clinical testing. In this study, an electrochemical biosensor was developed based on nanomaterials and the hybridization chain reaction (HCR) for highly sensitive and selective detection of the target miR-378 using K₃Fe(CN)₆/K₄Fe(CN)₆ as a redox indicator. MiR-378 is located on human chromosome 5q32 and serves as an important gene regulatory locus. Recent studies have found that aberrant expression of miR-378 is associated with cervical cancer, breast cancer, lung cancer, and other diseases. HCR is a simple and efficient isothermal amplification technique that does not require enzyme mediation and can be performed at room temperature. Evaluations of the specificity, stability, and sensitivity of the developed sensor revealed its ability to rapidly and specifically detect miR-378 in two hours with a detection limit as low as 100 cells in a volume of 400 µL, thereby indicating that this device could provide a novel approach for clinical diagnosis.

In this study, the composition and antibacterial activity of essential oil from the flower of Nyctanthes arbor-tristis were determined. The extraction was carried out utilizing the microwave-assisted extraction technique with a short extraction time of 60 min, yielding 0.342% (w/w). Separation and characterization were performed by gas chromatography-mass spectrometric analysis, identifying a total of 34 constituents, including major compounds: phenyl ethyl alcohol (26.1%), eucarvone (18.7%), furfural (10.7%), benzaldehyde (4.8%), phytol (4.7%), and methyl hexadecanoate (3.1%). In the next step, an agar disk diffusion assay was performed to assess the antimicrobial activity of the oil against four different bacterial strains, namely Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa, resulting in zones of inhibition measuring 9, 12, 11, and 9 mm, respectively. However, the broth macrodilution method was carried out against Staphylococcus aureus and Klebsiella pneumoniae, revealing minimum inhibitory concentrations of 2.5 and 5 mg/mL, respectively.