Journal of Analytical Chemistry最新文献

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.

A straightforward procedure is developed for the selective determination of alpha-tocopherol acetate (vitamin E) in oil-based cosmetic products, focusing on the evaluation of the sorptive capacity of human skin and the uniformity of the distribution of the preparation on its surface. The procedure is designed to determine vitamin E after application as an oil solution, relying solely on the analyte’s absorption without additional reagents, such as ascorbic acid or an alkali. The procedure involves vitamin E extraction with isopropanol and measuring an analytical signal by UV spectrophotometry. The calibration curve exhibits linearity within the range 0.02–0.1 mg of vitamin E/mL. The limit of detection for vitamin E, calculated from the calibration curve equation and its slope, is 0.5 µg/mL. This procedure has demonstrated reproducibility, selectivity, rapidity, and simplicity.

A method for the determination of phthalates in water is validated. It includes the sorption of hydrophobic components of a sample on a liquid chromatography column and the separation of analyte concentrated by online reversed-phase HPLC: for the quantitative determination of priority phthalates (PPhs) in surface waters at a trace level; qualitative assessment of the ratio of stable carbon isotopes ¹³C/¹²C in the PPh composition. It is shown that there is no contribution of PPhs from the laboratory background to the measurement results. The limits of determination (0.15−0.22 μg/L) and the accuracy of the determination (±δ = 10−20%) are found using online reversed-phase HPLC and the UV detection of the analytes. The boundary values for the ¹³C/¹²C isotope ratio are substantiated for a qualitative assessment of the results of measuring the Δ¹³C value in the structure of di(2-ethylhexyl) phthalate and its ingress into waters of Lake Baikal from biogenic and abiogenic sources is revealed. A procedure for determining PPhs by reversed-phase HPLC with online UV detection is tested in the field using a portable liquid chromatograph; the concentration ranges for di-n-butyl phthalate (from <0.15 to 1.6 μg/L) and di(2-ethylhexyl) phthalate (from <0.22 to 1.6 µg/L) in the coastal zone of Lake Baikal are evaluated.

A simple, rapid, and sensitive procedure is developed for the determination of hydroxylated polycyclic aromatic hydrocarbons (2-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 3-hydroxyphenanthrene, 2-hydroxyphenanthrene, 1-hydroxypyrene, and 6-hydroxychrysene) in urine by gas chromatography–mass spectrometry. Sample preparation is based on dispersive liquid–liquid microextraction with trichloromethane in an acidic medium. Derivatization is carried out in a heated injector port using the reagent N,O-bistrimethylsilyltrifluoroacetamide. The type of dispersing solvent is experimentally selected and the optimal ratio of the following factors, i.e., pH value, volume of dispersing solvent, and extraction time, is found using a three-factor experiment. A high-temperature capillary column NT-8 is used in a temperature gradient mode for analysis by gas chromatography–mass spectrometry. The linearity range of the calibration function is found to be 0.5–100 ng/mL. The developed procedure for determining hydroxylated PAH in urine is tested on urine samples from aluminum production workers.

A facile kinetic spectroscopic technique was devised and validated for the precise estimation of memantine hydrochloride. This method depends upon the measurement of various kinetic characteristics of the reaction between the drug and 1-chloro-2,4-dinitrobenzene in an alkaline medium at 70°C. The resultant memantine-dinitrobenzene complex exhibits a distinctive absorbance maximum at 290.5 nm. Spectroscopic analysis was conducted by scanning the complex within the 200 to 800 nm range using a Shimadzu UV-1900 spectrophotometer. Experimental conditions, including reagent concentration, base quantity, order of addition, and reaction temperature, were optimized. The reaction mechanism and stoichiometric ratio of the drug with the reagent were elucidated. Employing various kinetic methodologies such as initial rate, fixed time, and fixed absorbance under optimal conditions enabled the construction of calibration curves and accurate estimation of memantine hydrochloride. The method demonstrated linearity within the concentration range of 3.0 to 7.0 μg/mL. Precision assessment yielded satisfactory relative standard deviations of 2.05 for intra-day and 1.96 for inter-day precision studies. Accuracy studies revealed mean recoveries ranging between 98.55–102.34%. Moreover, the proposed method effectively determined memantine hydrochloride in a commercial formulation.

The adsorption of toxic ions Be(II), Bi(III), Cd(II), Cr(III), and Pb(II), and also noble metals Ag(I), Au(III), and Pd(II), from aqueous solutions is studied using carbon nanotubes (CNTs), a magnetic nanosorbent composed of CNTs and magnetic nanoparticles (CNT@MNP), and activated carbon (AC). An advantage of CNT-based adsorbents over AC in terms of capacity was demonstrated, with an increase of approximately 1.5–2 times. The adsorption capacity of the synthesized magnetic adsorbent depends on the morphology of CNTs grown on iron subgroup catalysts: nickel (CNT(Ni)), cobalt (CNT(Co)), and iron (CNT(Fe)). CNT@MNP exhibited superior performance over other carbon adsorbents in magnetic solid-phase extraction, effectively separating solid and liquid phases. Additionally, composite adsorbents containing CNT(Co) and CNT(Fe) were noted for their cost-effectiveness, as they yielded satisfactory results, surpassed those obtained with the individual CNT-based adsorbents. Procedures were developed using these carbon adsorbents and their performance in the determination of elements in aqueous solutions by arc atomic emission spectrometry was estimated.

A brief overview of chromatographic methods for determining free bisphenol A (BPA) in technical and food products is presented. Bisphenol A is used as a monomer in the production of some plastics and epoxy resins. The concentration of free BPA may exceed the permissible level in food plastic containers and in food products packaged in these containers. The maximum permissible concentration of BPA in water, in water bodies of domestic and drinking water and in cultural and household water use is 0.1 mg/dm³. In European countries, the migration value of BPA for plastics in contact with food products is 0.6 mg/kg. Gas chromatography with preliminary derivatization by the silylation or acylation of the analyte is most often used to determine BPA in plastics, food products, and biological fluids. Direct determination methods have been developed using gas-liquid chromatography on heat-resistant columns. Flame ionization, fluorometric, and mass-selective detectors are used as detection devices. HPLC with optical and mass-selective detectors is used to determine BPA. Thin-layer chromatography has also been used for determining BPA. Solid-phase extraction, liquid−liquid extraction, dispersive liquid−liquid microextraction, and a combined extraction method with separation in acetonitrile (QuEChERS) are used in BPA sample preparation.