Journal of Analytical Chemistry最新文献

In this study, a highly sensitive electrochemical sensor for the detection of bisphenol A (BPA) was developed by modifying a screen-printed carbon electrode (SPCE) with silver nanoparticles (AgNPs) and graphene oxide (GO) composites. The electrochemical properties of the modified electrode interface were meticulously investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy, employing 1.0 mM [Fe(CN)₆]^3–/[Fe(CN)₆]^4– as a redox probe. The findings demonstrate that the AgNPs/GO/SPCE composite exhibits superior electrical conductivity and facilitates rapid electron transfer compared to both GO/SPCE and SPCE alone. The electrochemical behavior of BPA on the AgNPs/GO/SPCE electrode was comprehensively studied using CV, revealing exceptional electrocatalytic properties for BPA oxidation. To assess the analytical performance, differential pulse voltammetry was employed. Results unequivocally show a significant improvement in the electrochemical responses when using AgNPs/GO/SPCE. Calibration curves exhibited linear ranges of 0.25–2.19 μM with a remarkable limit of detection of 0.046 μM for BPA. Furthermore, the established method was applied for the determination of BPA in plastic products, achieving satisfactory reproducibility and recovery. This novel AgNPs/GO/SPCE-based sensor holds promise for the sensitive and reliable detection of BPA in various environmental and industrial applications.

Cholelithiasis (gallstone disease) is a multifactorial condition characterized by the formation of gallstones. Investigation of the composition of gallstones is essential for understanding the mechanisms of their formation and addressing various practical issues. Currently, it remains unclear which protein components are involved in gallstone formation and how they are related to other components of the stones. This study demonstrates a potential for the qualitative and quantitative determination of amino acids in gallstones of men and women of different ages using gas chromatography (GC-17A chromatograph, Shimadzu, Japan). The analysis of the amino acid composition of gallstones involves the acid hydrolysis of the samples in 6 M HCl at 105°C for 12 h, followed by purification, derivatization of the isolated amino acids, and their determination by gas chromatography. This method allows for the identification of both D- and L-forms of amino acids. A statistical analysis of the obtained data was performed using the STATISTICA 6.0. The study found that cholesterol gallstones in women under the age 50 have the lowest amino acid content. In the amino acid composition of cholesterol gallstones, glycine, along with the L-forms of serine, alanine, and glutamic acid, predominates. Cholesterol gallstones with a mineral component are typical in elderly women (over 60 years old) and middle-aged men (from 37 years old) and exhibit higher amino acid contents than pure cholesterol gallstones. In this type of stones, glycine and the L-forms of leucine, glutamic acid, and aspartic acid predominate. The highest amino acid content was found in pigment stones, both in men and women over the age 55. The amino acid composition of pigment-type stones is dominated by glycine and the L-forms of glutamic acid, aspartic acid, leucine, and alanine. D-amino acids were not detected in cholesterol gallstones. However, D-aspartic acid was found in cholesterol stones with a mineral component and in pigment gallstones. These findings suggest that gas chromatography is a suitable method for studying the amino acid composition of gallstones.

Sepsis is a life-threatening organ dysfunction caused by a disorder in the regulation of a body’s response to infection. If sepsis is not recognized at an early stage and treatment is not started, it can lead to septic shock, multiple organ failure, and death. Sepsis diagnostics, traditionally based on the clinical picture and the detection of etiologically significant microorganisms in the blood and foci, has been improved in recent years through the search for and the implementation of various biomarkers. One of promising sepsis biomarkers is 3-(4-hydroxyphenyl)lactic acid (4-HPLA). In this work, an amperometric sensor modified with a molecularly imprinted polymer (MIP) of hydroxyphenyllactic acid is developed, and a fundamental possibility of determining 4-HPLA in model aqueous solutions using this sensor is demonstrated. Molecularly imprinted polymers are widely used in substance separation processes and in the fabrication of selective sensors. Among a variety of selective materials, polyimides are of particular interest. In this regard, MIP sensors with imprints of 4-hydroxyphenyllactic acid were developed based on a copolymer of 1,2,4,5-benzenetracarboxylic acid with 4,4'-diaminodiphenyl oxide. The sensors are obtained in two stages (stage I at 80°C, stage II at 180°C) using the non-covalent imprinting method. The high selectivity of the MIP sensors with respect to the target molecules was established. The analytical range of the acid is 0.0002−0.2 mg/L. The experimentally established limit of detection for 4-hydroxyphenyllactic acid is 4.5 × 10^–5 mg/L.

Glutathione persulfide (GSSH) is an important cellular metabolite involved in redox regulation and a potential therapeutic agent. Due to its instability and the lack of commercial GSSH standards, the development of procedures for its generation in situ and quantitative determination in various test systems is a problem of considerable current interest. In this work, conditions for the generation of GSSH in a reaction of oxidized glutathione with sodium sulfide with the fluorescent monitoring of released hydrogen sulfide were optimized. To derivatize the generated GSSH and reduced glutathione (GSH) with the formation of both derivatives in similar amounts, the reaction was carried out in the presence of an excess of N-ethylmaleimide. A procedure for the determination of GSSH based on the level of GSH in a model reaction using HPLC–mass spectrometry in the multiple reaction monitoring mode was described. The contribution of the GSH impurity in a solution of oxidized glutathione to the determined amount of GSSH and the detection limit of GSSH in the reaction mixture were found. The results are of interest for the preparation and mass spectrometric analysis of biologically relevant persulfides using various derivatizing agents.

The production, social, and ecological requirements for maintaining the quality of inland waters necessitated establishing a network of hydrochemical observation posts. The variability in the monitored indicators required implementing regular chemical and analytical studies. Conventional rigid statistical methods in analytical chemistry often fail to address the specifics of studying fuzzy experimental data, such as series of impurity concentration values in a river flow over space and time. In this context, alternative soft computing tools, particularly those based on neuro fuzzy hybrid algorithmic structures related to the ANFIS architecture, are more suitable. An analysis of chemicoanalytical data arrays for copper and zinc in the Volga River, considering water flow at various distances from the shore and depths, revealed a complex oscillatory behavior in the concentrations of both substances. This analysis concluded that the neuro-fuzzy processing scheme of the monitoring results enables a more in-depth study of the poorly understood processes of hydrochemical dynamics in systems far from thermodynamic equilibria, such as natural watercourses.

The composition of solid solutions in the KNd(SO₄)₂·H₂O–SrSO₄·0.5H₂O system, synthesized from aqueous solutions of KCl, NdCl₃, SrCl₂, and H₂SO₄, was studied by X-ray fluorescence spectrometry. Coefficients of calibration dependences for intensity vs. element concentrations were calculated for Nd, Sr, and K by the least-squares technique. A linear approximation function was used in determining potassium and a parabolic approximation function was recommended in determining neodymium and strontium. The obtained dependences are characterized by low (<1%) relative approximation errors. In the analytical ranges (wt %) for K 0.863−8.892, Sr 8.41−38.03, and Nd 5.296−29.30, the standard deviations were 0.012−0.028, 0.008−0.098, and 0.05−0.27 respectively.

The study demonstrates the potential for monitoring the dynamics of chocolate glaze aroma formation during conching using an artificial olfactory system based on an “electronic nose” with polymer- modified piezoelectric gas sensors. The samples were collected from an actual production environment, and mandatory quality control of their standard properties was conducted throughout the chocolate glaze conching process. The digitization and objective monitoring of the aroma development and maturation process were performed using a data matrix (recorded and calculated signals) from a piezoelectric sensor array. The sensor array, the responses of which correlate with specific physicochemical quality indicators of both semifinished products and final goods, was optimized beforehand. Correlations between the results of sensorometric analysis and the physicochemical quality indicators of confectionery glaze were revealed. Informative sensors were selected, with responses enabling the rapid assessment of standard characteristics, such as moisture content (based on the crown ether sensor with a Pearson correlation coefficient of R = 0.91) and acidity (based on the Tween-40 sensor with a Pearson correlation coefficient of R = 0.90–0.91). The most valuable information comes from monitoring the decrease in the amount of nonvolatile compounds, particularly in the total sugar content during conching, using signals from the Triton X-100 sensor (with a Pearson correlation coefficient of R = 0.89). As a criterion for the reproducibility of the qualitative and quantitative composition, we proposed a new digital characteristic of aroma—a set of binary sensitivity parameters from the “electronic nose” sensors—and developed a novel chemometric method for processing data sets for the test samples. The study demonstrates a potential for integrating an “electronic nose” into production for technological control, ensuring compliance with and optimization of recipes, and monitoring the conching process of chocolate glaze based on physicochemical indicators and digital characterization of the most unstable property—aroma. This approach allows for objective and reproducible quality assessment of confectionery products.

To study the physicochemical (including adsorption) properties of nanodiamond, it is necessary to reproducibly obtain a carbon surface of an individual particle without metallic impurities of an unknown composition. Such a surface can be obtained through an additional procedure of the deep purification of a commercially available sample. This work is devoted to a study of the composition of non-combustible impurities of detonation diamond nanopowder. Using inductively coupled plasma mass spectrometry, iron and titanium are identified as the main metallic components of the non-combustible residue, the presence of Cr, Ni, Zr, As, and Sb is qualitatively established. The expected composition of the main molecular ions formed on the surface of the non-combustible residue under laser desorption/ionization mass spectrometry conditions is presented. Based on the results of the mass spectrometric analysis, a version of two-stage chemical treatment of detonation diamond nanopowder is proposed, which made it possible to reduce the mass fraction of non-combustible impurities during annealing in air from 2.0 to 0.1%.

The study focuses on the specific features of zinc determination in dust emissions from gas cleaning systems used in an electrometallurgical plant used to process scrap metal. X-ray powder diffraction, energy-dispersive X-ray fluorescence spectrometry (EDXRF), and inductively coupled plasma atomic emission spectrometry (ICP–AES) were employed to identify the elemental and phase compositions of the dust emissions, including zinc oxide, zinc ferrite, halite, sylvite, and magnetite. Based on these compositions, an analytical procedure was developed. The proposed rapid energy-dispersive X-ray fluorescence spectrometry method for zinc determination in dust emissions involves constructing a calibration curve with matrix effect corrections. The relative deviation for zinc determination using EDXRF with matrix correction was 2.1%, while for ICP–AES it was 2.5%. The zinc determination method was tested on real samples of gas cleaning dust emissions.

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed to determine organic impurities in a combination drug containing levodopa and benserazide, frequently used in the treatment of Parkinson’s disease. The determination of impurities holds significant importance in combination products, as their higher occurrence impacts both the quality and bio-efficacy of the drug products. Thus, the current RP-HPLC method aims to identify organic impurities, providing simplicity, effectiveness, and reproducibility. A Zorbax SB C18 column (4.6 × 250 mm, 5 μm) was utilized, with a flow rate of 1.0 mL/min and a detection wavelength of 220 nm. The analysis was conducted in isocratic mode with an ambient (25°C) column temperature and a 5°C autosampler temperature. Further, enhanced peak resolution was achieved by employing an iron pair agent. All impurities were effectively separated, and peak purity analysis confirmed the absence of interference for levodopa and benserazide. Accuracy, precision, and linearity were well within acceptable criteria, with the method signifying a correlation coefficient above 0.995 for known impurities of levodopa and benserazide. The method validation, following ICH quality guidelines, exhibited the specificity of the developed method, while the robustness study confirmed its reliability under diverse conditions. Thus, mutual results indicate the pragmatism and applicability of the developed method, reinforcing safe and efficacious therapeutics for patients.