Journal of Analytical Chemistry最新文献

Drift ion mobility spectrometry (DIMS) is a well-recognized method for studying the structure of matter. It is widely used for the identification of narcotic and explosive substances, as well as in biomedical research as part of hybrid mass-spectrometric techniques. An experimental method based on signal multiplexing with the Hadamard transform has a significant impact on the quality of the data obtained. However, artifacts in the decoded multiplexed signal remain a major obstacle to the expansion of this method. A number of scientific groups have proposed a variety of approaches to suppress artifacts, but the reasons for the artifact formation remain controversial. Along with the search for and development of applied methods for reducing the effect of artifacts, the authors consider it advisable to develop a theoretical basis for the appearance of modulation errors, which will ensure a mathematically correct elimination of these errors from the results of Hadamard transformations. In this work, using an ion mobility spectrometer with a Faraday plate detector, we investigated possible reasons for the systematic signal modulation error. The two proposed reasons include the Coulomb repulsion of ion packets and the heterogeneity of the contributions of individual sections of pseudorandom sequences. We also described a mathematical procedure for artifact formation, which takes into account the effect of the second reason. A comparison of mathematically calculated artifacts with the experimentally observed ones was done for a statistically significant number of modulating sequences, on the basis of which we concluded that the heterogeneity of the contributions of individual sections of pseudo-random sequences has a predominant effect.

The formation of positive and negative ions in the homologous series of trinitrobenzene, trinitrotoluene, and trinitroxylene was studied by mass spectrometry. Positive and negative ion mass spectra were acquired through electron ionization and resonant electron capture methods on a quadrupole mass spectrometer within a GC–MS system. The ionic compositions of the opposite-sign spectra display both similarities and complementary differences that aid in compound identification. These features are interpreted through quantum chemical calculations of the thermal effects associated with molecular ion fragmentation. For trinitrobenzene, close correspondence between the composition of positive and negative ion peaks in the spectra reflects comparable energy requirements for nitro group elimination via the simple C–N bond cleavage and the nearly equal exothermicity of NO release through the nitro–nitrite rearrangement. In contrast, the methyl-substituted compounds, trinitrotoluene and trinitroxylene, exhibit pronounced differences: their positive ion spectra are dominated by products of multistage decays initiated by the exothermically favorable release of a hydroxyl group due to the ortho effect, whereas the analogous processes in negative ions demand additional energy input. The observed abundance of exothermic fragmentation pathways provides insight into the relative stability of molecular ions and suggests parallels with the mechanisms of explosive transformations.

Atmospheric pressure laser plasma ionization technique is studied in application to the problem of tea classification according to the composition of volatile compounds without sample preparation. Tea leaf samples from nine different trade names were studied. The obtained mass-spectrometric data were clustered using chemometric methods without detailed component-by-component interpretation of the mass spectra. A comparative study of six methods, i.e., principal component analysis, K-means, and hierarchical clustering (unsupervised methods), as well as support vector machine, logistic regression, and multilayer perceptron neural network (supervised methods), was performed. It was shown that the most effective method for classifying tea samples is logistic regression combined with recursive feature elimination with cross-validation.

The possibilities of GC–MS identification of the products of free-radical chlorination of cyclic ethers, namely, tetrahydrofuran, 2H-tetrahydropyran, and 1,4-dioxane directly in reaction mixtures (without isolation) are considered. The number of chlorine atoms in these products can be determined unambiguously using electron ionization mass spectra. The complexity of this problem is explained by the large number of possible congeners and isomers (e.g., in the case of 2H-tetrahydropyran, their number is 234), as well as insignificant informational maintenance. The absence of gas chromatographic retention indices (RIs) on standard nonpolar polydimethylsiloxane stationary phases even for simplest chloro derivatives of mentioned cyclic ethers makes impossible the calculation of increments, which allow interpretation of data for more chlorinated products. As a result, the data for compounds of other series (including alicyclic ones, having different conformations) should be used as a rough approximation. Nevertheless, by this way, some simplest products of tetrahydrofuran and 1,4-dioxane chlorination were identified. Besides that, the joint interpretation of mass spectrometric and gas chromatographic data allowed us to identify three from four isomeric hexachloro-1,4-dioxanes.

This study presents a new highly sensitive approach to the determination of eight steroidal sapogenins—hecogenin, neoruscogenin, ruscogenin, gitogenin, diosgenin, sarsapogenin, yamogenin, and tigogenin—by comprehensive 2D high-performance liquid chromatography coupled with tandem mass spectrometry in the multiple reaction monitoring mode. The ionization characteristics of sapogenins were studied under atmospheric pressure chemical ionization with positive ion detection. Tandem mass spectra of the selected precursor ions were analyzed, and the main pathways of their collision-activated dissociation were identified. Combining 2D chromatographic separation with mass-spectrometric detection enabled the development of a method for the simultaneous quantification of steroidal sapogenins, achieving limits of detection from 0.7 to 2.9 μg/L. The approach was validated and successfully applied to the analysis of plant extracts rich in steroidal saponins, including Yucca gloriosa, Yucca treculeana, Yucca filamentosa, and Yucca aloifolia.

The search for biomarkers for the noninvasive diagnosis of diseases, in particular, immunoglobulin A nephropathy (IgAN) is an urgent task. Urine samples from patients with a confirmed IgAN and from healthy volunteers were analyzed by high-performance liquid chromatography—high-resolution mass spectrometry. A number of native peptides found only in IgAN samples were identified using the Mass Frontier and PEAKS Studio software.

This study presents the results of the identification and quantification of polycyclic aromatic hydrocarbons (PAHs) in atmospheric aerosol particles. Suspended particulate matter (PM_2.5) was collected in Arkhangelsk, a major city in the Arctic zone, using glass fiber membrane filters with a pore size of 1.6 μm. PAHs were extracted from the particle surfaces by ultrasonic extraction in methanol. Gas chromatography coupled with high-resolution mass spectrometry (GC–HRMS) employing an Orbitrap analyzer enabled limits of detection for the target analytes ranging from 0.020 to 1.5 ng/m³ (per 1.8 m³ of air). Concentrations of individual PAHs varied from 1.2 to 4.0 ng/m³, with total concentrations of the 18 target PAHs being 17 and 32 ng/m³ for samples 2 and 1, respectively. Diagnostic ratios of PAH isomers indicated that pyrogenic sources, including incomplete fuel combustion and biomass burning, were the dominant contributors. Non-targeted screening identified 31 compounds, including oxygenated derivatives of phenanthrene and anthracene, nitrogen-containing PAHs, and high-molecular-weight PAHs, such as benzo[j]fluoranthene, benzo[e]pyrene, and perylene. These environmentally significant pollutants were present in concentrations of approximately 1–2 ng/m³.

This study presents a rapid and a highly sensitive method for determining seven major biologically active lignans—lyoniside, ssioside, hydroxymatairesinol, secoisolariciresinol, nortrachelogenin, pinoresinol, and matairesinol—in plant extracts by ultrahigh-performance liquid chromatography coupled with tandem mass spectrometry in the multiple reaction monitoring mode. Analytes ionization under electrospray ionization and atmospheric pressure chemical ionization conditions was studied. We analyzed tandem mass spectra of selected precursor ions and identified the main pathways of their collision-induced dissociation (CID). The optimization of reversed-phase HPLC separation parameters and mass spectrometric detection enabled the development of a method for the simultaneous determination of the analytes in plant extracts, achieving an analysis time of less than 6 min and detection limits ranging from 0.72 to 9.0 μg/L. The developed approach was validated and tested using extracts from compression wood of coniferous and deciduous trees, stems of wild rosemary, and above-ground parts of several berry plants.

Bisphenol A (BPA) is widely used as a hardener in the plastics industry. However, its release and circulation in ecosystems lead to contamination of drinking water, which negatively impacts the human endocrine system. Therefore, there is a need for simple and efficient tools for monitoring BPA. This study presents a combination of two approaches for this purpose: the use of magnetic particles (MP) as antibody carriers and immunochromatographic test strips for detecting labeled immune complexes. The visual limit of detection (LOD) of BPA was 10 μg/mL, the instrumental LOD was 55 ng/mL, and the working range of detectable concentrations was 0.1–10 μg/mL. The efficacy of using the MP conjugate for analyte concentration was demonstrated, resulting in an approximately 200-fold reduction of the LOD. The developed immunochromatographic assay (ICA) is suitable for the qualitative monitoring and quantitative determination of BPA in drinking and natural water samples (with 94–106% recoveries).