Journal of Analytical Chemistry最新文献

A procedure is developed for determining gluten in commercial food products using ultra-high-performance liquid chromatography−tandem mass spectrometry. A key feature of the procedure is minimizing the impact of variations in the gluten protein content and composition on the result of quantitative analysis, achieved by summing the responses of several marker peptides. The results show that the overall limit of detection by the developed procedure is 10 mg/kg of gluten proteins in food products. It is shown that an increase in the number of marker peptides improves the reliability of the method in analyzing food products with varying gluten protein compositions. This approach ensures an improvement in the accuracy of the control of gluten content, which is important for the products labeled “gluten-free.”

This article addresses a key aspect of direct current (DC) arc atomic emission spectrometry—the influence of chemically active additives on the performance characteristics of the determination of refractory elements in refractory matrices. To achieve this goal, the authors critically reviewed a series of their previously published results and compared them with relevant published data concerning both the mechanisms of additive action and their applications. Drawing on more than 25 years of research, the authors identified general trends and demonstrated advantages of fluorinating agents, such as AlF₃, AgF, BaF₂, SrF₂, and ZnF₂. These studies showed that the listed additives serve as universal modifiers in the analysis of refractory matrices and significantly enhance selectivity, sensitivity, and analytical accuracy of DC arc methods. Among them, zinc fluoride proved to be the most effective fluorinating agent for all matrices studied. Its use allowed us to lower the limits detection for refractory elements. The effect of fluorine-containing additives—AlF₃, AgF, BaF₂, SrF₂, and ZnF₂—on the the selectivity of the evaporation of a number of low-volatility elements from refractory matrices, including zirconium oxide, aluminum oxide, and graphite powder, in a DC arc was studied. It was found that the additives promoted the formation of highly volatile fluorides of the studied impurity elements, resulting in their fractional evaporation from the electrode crater relative to the base element. This behavior led to a marked increase in the intensity of spectral lines of impurity elements, a decrease in the continuous spectral background, and, consequently, lower limits of detection for low-volatility elements. Among all additives, zinc fluoride exhibited the highest efficiency. Its application lowered limits of detection by two to three orders of magnitude and improved the reproducibility of the results by approximately a factor of two compared to the analyses performed without additives. Moreover, the use of zinc fluoride eliminated systematic errors due to differences in composition between the analyte and reference samples, thereby further improving the accuracy of the analysis results.

A method for the preconcentration of trace mercury in water has been proposed, utilizing ammonium pyrrolidinedithiocarbamate (APDC) as the chelating agent and the non-ionic surfactant Triton X-114 as the extractant. The trace mercury present in the water is concentrated into the surfactant phase via cloud point extraction (CPE), and is determined by hydride generation atomic fluorescence spectrometry (HGAFS). The optimal determination conditions were successfully obtained by optimizing the cloud point extraction conditions and atomic fluorescence test conditions, such as pH, chelating agent dosage, extractant dosage, equilibrium temperature and time, carrier solution (HCl), and reducing solution (KBH₄). Under the optimal extraction conditions, it was demonstrated that the detection limits of the APDC-CPE-HGAFS method can reach 0.002 μg/L, which is one order of magnitude lower than that of the current standard method. The standard addition method was employed for recovery experiments, with recovery rates ranging from 92.5 to 98.5%. The relative standard deviation of the measured values (n = 6) ranged from 4.2 to 8.1%. This indicates that the method possesses the advantages of a low detection limit, good precision, and high accuracy.

Common juniper (Juniperus commúnis L.), Cypress family (Cupressaceae), is a promising source of biologically active substances for the treatment and prevention of chronic diseases. Extracts of juniper needles and fruits are analyzed by high-resolution HPLC–MS and thermal desorption (TD) GC–MS. Six hydroxybenzoic acids and four hydroxycinnamic acids were identified on the chromatograms of the extracts recorded in the full scan mode. The content of salicylic, p-hydroxybenzoic, gallic, coumaric, and ferulic acids was estimated at 0.03–17 mg/L. In the TD-GC–MS mode, peaks of substances were recorded in the range of retention times 9–25 min (by retention indices from 900 to 1700). For a more reliable identification, experimental retention indices were calculated and compared with those presented in the literature. It was suggested that the presence of substances such as cosmene, pinocarveol, and 2-pinen-4-one in the chromatograms can serve markers of the presence of juniper berries in the dietary supplement of juniper needles.

This article describes a rapid, simple, and highly selective gold nanoparticle (AuNP)-based colorimetric approach to isocarbophos detection. When isocarbophos is absent, AuNPs in a solution containing the water-soluble polyelectrolyte polydiallyldimethylammonium chloride (PDDA) and an isocarbophos nucleic acid aptamer, PDDA and the aptamer bind electrostatically, and the AuNPs do not aggregate. When isocarbophos is present, it specifically binds to the aptamer, which does not bind PDDA. The free PDDA then induces AuNP aggregation. Effects of buffer solution, pH value, storage time, cationic polymer PDDA concentration, and aptamer concentration on this assay were analyzed, and under optimized conditions, an isocarbophos detection limit of 5.76 nmol/L was achieved, with a linear detection range of 70–480 nmol/L. Recovery tests on lake water samples demonstrated that this method offers good selectivity and anti-interference properties.

Medicinal plants are a valuable source of biologically active substances used to prevent and treat diverse diseases. The major classes of these compounds—alkaloids, glycosides, flavonoids, essential oils, tannins, polyphenols, and polysaccharides—exhibit broad pharmacological activities, including antimicrobial, anti-inflammatory, antiseptic, and antioxidant effects. Phytochemical screening of plant extracts plays a crucial role in identifying these compounds and supporting the development of new therapeutic agents. In this study, a spectrophotometric phytochemical screening was performed to evaluate alkaloids, tannins, flavonoids, phenolic compounds, steroid cardiac glycosides, and polysaccharides and the antioxidant activity of extracts from three medicinal plants from different families, milk-ripened oats (Avena sativa L.), madder root (Rubia tinctorum L.), and Scotch heather (Calluna vulgaris L.), was assessed. High-performance liquid chromatography was used to achieve a more detailed chemical profile. Both conventional solvents (methanol, ethanol, water-alcohol mixtures, water, acetonitrile) and a new class of solvents, deep eutectic solvents, were used as extractants. Ultrasound-assisted extraction proceeded at 40–80°C for 10–60 min. The optimal extraction conditions were found for the major compound groups: 80°C for 60 min with conventional solvents, 50°C for 30 min for Calluna vulgaris L. with deep eutectic solvents, and 60°C for 30 min for madder root and oats with deep eutectic solvents. The results demonstrate that deep eutectic solvents effectively extract the target bioactive substances under milder conditions, underscoring their potential as environmentally sustainable extractants in phytochemical research.

Simultaneous determination of acetaminophen and uric acid in biological samples was performed using differential pulse voltammetry (DPV) on a glassy carbon electrode coupled with orthogonal signal correction-partial least squares (OSC-PLS). The optimum parameters were set at pH 8.0, a scan rate of 10 mV/s, and a pulse height of 50 mV. Both analytes showed peaks at about 390 mV. OSC-PLS was performed to solve the interference problem in the voltammograms. DPV calibration showed broad dynamic ranges of 10.0–220.0 and 10.0–210.0 µmol/L for acetaminophen and uric acid, respectively. The method was successfully applied to human plasma and urine samples without any pretreatment.

Currently, the most common method of detecting lithium ions in salt lake water and oilfield production water is instrumental analysis, such as atomic emission spectroscopy, atomic absorption spectroscopy, ion chromatography, ultraviolet spectrophotometry, and complexometric titration. However, for instrumental analysis, the equipment is expensive, the operation is complicated, and the samples require complex pre-processing, which makes it difficult to detect lithium on-site. For complexometric titration, the operation steps are cumbersome during the production process, which limits its suitability for on-site inspection. As lithium’s position in industrial production gradually increases, the demand becomes increasingly large, and fluorescent probe detection technology, with simple operation and high selectivity, is gradually entering the field of view. Studies have shown that crown ether compounds have a complexing effect on alkaline earth metals. Among them, crown ether compounds such as 12-crown-4, 14-crown-4, and dibenzo-14-crown-4 show excellent selectivity in lithium ion recognition experiments because their internal pore size matches the size of lithium ions. Other cations are difficult to form complexes with them. Therefore, crown ether compounds can be used as recognition groups for lithium ion fluorescent probes. This article will introduce the existing instrumental analysis and titration methods for detecting Li⁺, explain the current research progress of fluorescent probes based on crown ether compounds, and put forward goals and prospects regarding their poor solubility.

A method for determining the carbon content of carbonate–aluminosilicate glasses by electron probe microanalysis is proposed and implemented. To take into account the CK_α signal arising due to the conductive carbon coating and beam-induced carbon contamination, we used a calibration approach with carbonate reference samples of different carbon concentrations. The analytical signal was determined as the area under the first CK_α peak in the recorded X-ray spectrum, which ensured the account of the effects of carbon–oxygen bonding and interactions with other elements on the CK_α peak shape and position. Optimal conditions for recording spectra in the CK_α region were found for accurate carbon determination. Linear calibration curves obtained at 5 kV using carbonate standards were highly reproducible, with relative standard deviations of 1–3%. The method ensures limits of detection of 0.2–0.4 wt % and limits of quantification of 0.6–1.2 wt %.

Nickel-titanium-palladium shape memory alloys show broad application prospects due to their shape memory effect and superelasticity in high-temperature environments. Nickel serves as the pivotal constituent in the material system, with its concentration and spatial distribution critically governing the phase transition temperature, mechanical performance, and high-temperature stability, thereby dictating the alloy’s functional behavior. A gravimetric method was developed for nickel determination in Ti–Ni–Pd shape memory alloys. Key analytical parameters, including dissolution conditions, interference effects from matrix elements, dimethylglyoxime concentration (optimized at 30 mL of 10 g/L solution), and precipitation incubation (90 min at a controlled 70°C), were systematically investigated. Method validation demonstrated excellent precision (RSD < 0.5%, n = 7) and accuracy (99.4–100.4% recovery rates) through spike recovery experiments. A key advancement lies in elucidating the competitive coordination mechanism between palladium and nickel complexes with dimethylglyoxime, which enabled the development of a masking protocol to mitigate Pd interference. These optimizations significantly improved methodological robustness, achieving above 99% recovery rates for nickel in complex matrices while maintaining operability under routine laboratory conditions.