Journal of Analytical Chemistry最新文献

Complex compounds of Cu, Ag, Pd, Pt, and Au with dithizone (diphenylthiocarbazone) were studied by surface-assisted laser desorption/ionization from nanocrystalline silicon. The study demonstrated that all investigated complexes ionize efficiently in the negative ion mode, forming molecular ions and one or more types of fragment ions. The limits of detection for the metal dithizonates were determined. A possibility of coupling laser desorption/ionization mass spectrometry with single drop microextraction for metal detection was explored. Factors affecting the concentration factor were examined, and the optimal conditions for performing single drop microextraction in gold determination were found. The limit of detection for gold is 5 pg/mL.

A contactless method is proposed for determining the mass fraction of milk fat in bottled milk by the diffuse reflectance LED at the wavelengths 365, 390, 850, and 880 nm using a smartphone and a specialized device. The analytical signal was recorded using OnePlus 10 Pro and iPhone 14 smartphones, equipped with PhotoMetrix PRO®, ColorGrab, and RGBer applications, as well as using an FTIR spectrometer for the near-IR region (4000–10 000 cm^–1). Specialized software, including TQ Analyst, The Unscrambler X, and XLSTAT, was used to process the experimental data. It was found that using all LEDs with different wavelengths simultaneously yielded results with the smallest relative deviation compared to using individual LEDs. Additionally, a slight change in the diffuse reflectance of milk through polyethylene terephthalate-based packaging was identified, which enabled contactless analysis without opening the packaging. The milk fat content of the test milk samples was evaluated using a multivariate calibration data algorithm—partial least squares regression. The relative standard deviation of the analysis results did not exceed 8%. The consistency of the analysis results was confirmed by FTIR spectroscopy in the near-IR region.

Thallium (Tl), a heavy metal, has potentially harmful effects on human health due to its extreme toxicity. The determination of Tl is critical, and thus, there is a need for the development of electrochemical sensors that can swiftly identify its presence in the environment. A one-step hydrothermal synthesis of Prussian blue (PB) was utilized to adsorb thallium and electrochemically activate PB. The structure and morphology of PB were characterized through a scanning electron microscope, X-ray energy spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The PB-modified electrode’s determination performance was optimized using the square wave voltammetry method. This included the optimization of support electrolyte, pH, deposition potential, and deposition time. Under optimal experimental conditions, the electrode demonstrated a favorable electrochemical response to thallium concentrations between 10 and 500 μg/L, with a detection limit of 1.94 μg/L. In summary, this sensor’s outcomes are satisfactory and enhance the utility of PB nanomaterials in electrochemically detecting the heavy metal Tl.

Stable electrospray generation from fused silica tips is critical for mass spectrometry, but these tips can degrade, leading to droplet formation and poor spray. A quick, cost-effective method has been developed to rejuvenate these tips, extending their usability and reducing expenses. The protocol involves sequentially rinsing pulled fused silica emitters for electrospray ionization (ESI) with acetone, water, an aqueous sodium hydroxide solution, water, and acetone again, followed by air drying. Next, the tip is dipped into a hydroxy-terminated polydimethylsiloxane solution and air dried. A final acetone rinse completes the process, which does not require disassembling the fluidic flow system or removing the nESI tip from its mount. This reconditioning not only prevents droplet formation but also restores the correct spray pattern, ensuring stable electrospray for 1–2 weeks. Tips can undergo multiple reconditionings. Although the protocol may lead to transient contaminant peaks, these diminish over 24 hours, and a list of potential contaminants is provided.

A procedure is developed for determining acetone acylhydrazones based on the formation of a colored complex with copper(II) ions of the composition Cu : reagent = 1 : 2 in ammonia solutions, its subsequent extraction with chloroform, and measurements of the absorbance of the extracts at 553 nm (ε = 128 L/(mol cm)); the analytical range is 80.0–590.0 mg/L; the relative error is <2.80%. Using acetone heptanoylhydrazone as an example, it was shown that the reagent in the complex compound is quantitatively extracted in the pH range 7−10 with a single extraction for 3 min; for its complete extraction, a twofold excess of copper(II) is sufficient. The spectra of the homologue complexes of the studied series of acetone acylhydrazones are similar. The high hydrolytic stability of the reagents in a narrow pH range of 9‒10 is established by the spectrophotometric method. The procedure is tested on solutions obtained in the study of the adsorption of reagents on chalcopyrite. The precision of the analysis results is verified by the addition method.

A colorimetric device is proposed for identifying and detecting the adulteration of various types of starch and flour by diffuse reflection of UV and IR radiation from LEDs. The color characteristics of the samples (RGB channel values) were determined using cameras on OnePlus 10 Pro and iPhone 14 smartphones with installed applications PhotoMetrix PRO, ColorGrab, and RGBer. Near-infrared spectra (4000–10 000 cm^–1) were recorded on a Fourier-transform infrared spectrometer. Specialized software packages, including TQ Analyst 9, The Unscrambler X, and XLSTAT, processed the dataset of colorimetric and spectral characteristics. The identification features included clustering patterns for different types of starch and flour in principal component analysis and hierarchical cluster analysis. Optimal wavelengths for determining the quality of adulteration of the tested samples were identified: for starch, the simultaneous use of all LEDs (365, 390, 850, and 880 nm); for flour, LEDs with wavelengths of 365 and 390 nm. The qualitative adulteration was assessed using graphs of the dependence of the F1 component on the mass fraction of the added foreign substance in the starch or flour. The effectiveness of the colorimetric method was confirmed by Fourier-transform infrared spectroscopy in the near-infrared region.

Sodium alkylbenzene sulfonates (ABS), or linear alkylbenzene sulfonates (LAS), are among the most common synthetic anionic surfactants and water pollutants, capable of causing both acute and chronic toxic effects on aquatic organisms. The selective determination of sodium alkylbenzene sulfonates as a distinct class of anionic surfactants in complex natural matrices is feasible by gas chromatography with mass spectrometric detection (GC–MS) in the form of linear alkylbenzenesulfonic acid methyl esters (LABSA ME). The behavior of LAS and LABSA ME was studied under ascending high-performance thin-layer chromatography (HPTLC) using Kieselgel 60 F₂₅₄ and Sorbfil plates to purify extracts and preconcentrate analytes. A mixture of n-hexane with methanol (23 : 1, v/v) is proposed as a mobile phase. Under these conditions, sodium alkylbenzene sulfonates remain at the start line, while their derivatives (LABSA ME), obtained by methylation with trimethyl orthoformate in the presence of trifluoroacetic acid (yield η = 98%), form zones characterized by retention factors R_f of 0.62–0.71 on Kieselgel 60 F₂₅₄ and Sorbfil plates, respectively. The repeatability of R_f values is characterized by a relative standard deviation of 6.1 and 5.9%, respectively (n = 16). The completeness of the extraction (95.0–100.0%) of analytes from the plates is noted using descending HPTLC with acetonitrile. The applicability of the HPTLC method for preconcentrating analytes and purifying extracts is demonstrated using real water samples. Using GC–MS with electron impact ionization, concentrations of sodium alkylbenzene sulfonates were found in water sampled from the southern basin of Lake Baikal at a depth of 400 m (0.24 ± 0.02 µg/L) and in water obtained from melting snow collected from the ice of the Krestovka River at its mouth near the settlement of Listvyanka (31.1 ± 1.0 µg/L).

The work focuses on the development of a fluorimetric version of the fingerprint method based on conducting indicator reactions in the presence of a test sample. Observation of these reactions over time provides a more detailed information compared to batch methods, thereby improving sample recognition and enabling quantitative analysis. The proposed indicator reaction utilizes a commercial carbocyanine dye and 4-dimethylaminobenzaldehyde, whose interaction results in a decrease in fluorescence intensity and changes in absorbance over time. Three fluoroquinolones—moxifloxacin, levofloxacin, and ofloxacin—selectively change the signal in concentrations of 1 μM or higher, while other drugs, including different fluoroquinolones, do not interfere with the determination. Ofloxacin was detected in human urine samples at various times post-drug intake. A potential of using the same indicator reaction for sample recognition was demonstrated on examples of apple juices, soil extracts, and meat of varying freshness. Chemometric methods, including linear discriminant analysis, were used for data processing. The method achieved 97% accuracy in discriminating fifteen apple juice samples, 94% accuracy for ten apple juices from 2022 and 2023, 99% accuracy for ten soil samples, and successfully determined the freshness of five meat samples.

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.