Analytical Sciences最新文献

Polyunsaturated fatty acids (PUFAs) are essential dietary components. However, they must be obtained from food because the human body cannot synthesize them in sufficient quantities. Furthermore, PUFA content can vary slightly depending on the type of food and storage conditions, making it necessary to establish accurate and highly sensitive methods for their quantification. However, their sensitive determination remains challenging because of the poor ionization efficiency of conventional liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-MS analyses. In this study, we developed a highly sensitive LC with tandem mass spectrometry (LC-MS/MS) method for PUFA analysis based on permanently charged derivatization using TPP-AEP. This derivatization reagent has a quaternary ammonium structure, which is required for efficient ionization under mild electrospray ionization (ESI)-MS conditions. Consequently, the [M]⁺ ions of PUFAs derivatized with TPP-AEP were detected with high sensitivity. Solid-phase extraction (SPE) was used for sample preparation to remove impurities. Furthermore, a C18 column was used for LC separation with an acidic mobile phase to achieve good peak shapes and stable detection sensitivity in PUFA analysis. The developed method exhibited excellent linearity (r² ≥ 0.9983) and achieved a low limit of quantification in the range of 2.80-3.29 ng/mL for the examined PUFAs (5,8,11,14,17-eicosapentaenoic acid, 4,7,10,13,16,19-docosahexaenoic acid, arachidonic acid, and linoleic acid). Application of the method to PUFAs extracted from muscle tissues of four marine fish species demonstrated that the combination of lipid extraction, alkaline hydrolysis, derivatization, SPE, and LC-MS/MS allowed for the quantification of both free and total PUFA content with high sensitivity.

In this study, we demonstrate that the nanoscale morphology of BiVO₄ photoanodes can be quantitatively translated into optical absorption features, and further into PEC behavior, through a combined convolutional neural network (CNN) and Gaussian Mixture Regression (GMR) framework. CNN models successfully predicted UV-Vis spectra directly from SEM images, showing that multiscale morphological information-especially subsurface contrast captured by BEI-is correlated with two major interband transitions (Bi 6s → V 3d, O 2p → V 3d). Using these spectra as descriptors, the GMR model reconstructed full J-V curves with high accuracy, enabling PEC performance prediction from optical data alone. Scrutinizing the relation between the J-V and UV-Vis curves further identified a single spectral descriptor: the inflection point near ~ 360 nm, which consistently distinguished high- and low-performing samples in the spectra and corresponds to the O 2p → V 3d transition. This trend was also confirmed in the experimentally measured spectra of newly prepared samples. This feature is tentatively attributed to oxygen-related electronic structure perturbations associated with morphology-dependent variations in local coordination and disorder. Although the descriptor was identified for BiVO₄ photoanodes prepared by a single MOD route, this work shows that UV-Vis spectra, despite their simplicity, contain sufficient encoded morphological information to act as a fast, nondestructive probe for PEC measurements.

In this work, a flexible and environmentally compatible thin film, consisted of cellulose and polypyrrole, was prepared and used as a new thin film microextraction sorbent for adsorption and determination of trace amount of methylnaphthalene, anthracene and pyrene from aqueous samples. Analytes were determined by gas chromatography equipped with a flame ionization detector. polypyrrole was used as a modifier due to its porous structure and good mechanical stability in aqueous solution. Pyrrole monomers deposited on cellulosic substrate were polymerized through oxidative chemical polymerization. Extraction of analytes from sample solution to the cellulose/poly pyrrole film was performed through π-π interactions between the sorbent and polycyclic aromatic hydrocarbons (PAHs). Extraction efficiency was studied by changing parameters such as desorption solvent, time of desorption, volume of desorption solvent, salt concentration, temperature and extraction time were optimized. The detection limits of 1.40, 0.60 and 0.45 µg L^-1 were obtained for methylnaphthalene, anthracene and pyrene, respectively. The method showed good linearity in the concentration range of 4-3000, 2-1000, and 1-500 µg L^-1 for methylnaphthalene, anthracene and pyrene, respectively. Intra- and inter-day precision were in the range of 6.0-8.0% and 12.0-15.0%, respectively. Finally, PAHs were determined in real samples by this method. Recovery for real samples was in the range of 53-102%.

In recent years, microchemical devices have garnered increasing attention for enabling highly efficient chemical processes using minute sample volumes while offering advantages such as compactness and low environmental impact. In this study, a rotating microfluidic device capable of processing sample volumes on the order of several hundred microliters was developed utilizing centrifugal force as the driving mechanism. The device was designed to streamline labor-intensive solid-phase extraction (SPE) procedures commonly used in food analysis pretreatment. A centrifugal microfluidic device featuring a conditioning unit for SPE column preparation and a pretreatment unit for sample processing was developed. A validation study was conducted using this device on vitamin B1 (thiamine) retained on an SPE column. The measurement results met the relevant guidelines, and the method employing this device reduced processing time compared to conventional methods. As a preliminary evaluation, ascorbic acid 2-glucoside was also tested as a flow-through-mode analyte. However, device-associated chromatographic interference precluded confirmation of the quantitative validity of the method. Thus, this device is expected to contribute to labor and space savings as well as reduced environmental impact in food analysis pretreatment. However, further device design improvements and additional validation are required to expand its range of applicable targets.

In microjoule high pulse repetition frequency laser induced breakdown spectroscopy systems, the traditional single-variable parameter optimization method can only analyze the effects of scan speed and laser frequency independently, without considering the interaction effect between these two factors. To address this issue, an optimization strategy based on energy deposition rhythm (EDR) was proposed for the proportional optimization of scan speed and laser frequency. To begin with, the interaction between scan speed and laser frequency was analyzed using two-factor analysis of variance. Based on this, the effects of proportionally increasing scan speed and laser frequency on spectral signals were investigated by maintaining a constant ratio between the two parameters under different EDR conditions, followed by quantitative analysis based on the optimized spectral signals. The results indicated that, at a fixed EDR, proportional increases in scan speed and laser frequency maintained a constant spatial interval between adjacent laser pulses, thereby reducing the interference caused by pulse-spacing variations in local ablation overlap and related ablation conditions. Meanwhile, this proportional increase also resulted in a larger number of laser pulses contributing within the fixed 20 ms integration window owing to the increase in laser frequency, thereby enhancing the accumulated spectral emission while maintaining signal stability. The accumulated spectral intensities of Mg, Mn, and Fe increased by approximately 4-9, 5-10, and 4-10 times, respectively. The most pronounced quantitative improvement was observed under EDR = 1/400, where the R² values for Mg, Mn, and Fe increased from 0.8826, 0.9516, and 0.9061 to 0.9745, 0.9722, and 0.9778. This study provides a simple and broadly applicable strategy for optimizing high pulse repetition frequency LIBS signals and improving multi-element quantitative analysis performance.

In situ X-ray diffraction (XRD) measurements are widely used to investigate structural changes and often generate large XRD datasets. Although principal component analysis (PCA) and Rietveld refinement are effective tools for data analysis, they generally require additional physical interpretation or structural models, making the screening of large datasets challenging. To address this challenge, we propose a model-free method based on time-dependent correlation functions for directly tracking structural changes in large in situ XRD datasets without requiring crystallographic models or profile fitting. The effectiveness of the proposed method was demonstrated using in situ XRD datasets collected during the amorphization of zeolites over a temperature range from room temperature to 1000 °C. The proposed method successfully tracked dehydration and amorphization processes directly from in situ XRD datasets and showed good agreement with the trends observed in differential thermal analysis (DTA) and thermogravimetry (TG) measurements. These results demonstrate that the proposed method provides a practical tool for screening and tracking structural changes in large in situ XRD datasets.

Acrylamide (AA) is a highly polar compound that exhibits poor retention and low selectivity in conventional reversed-phase LC-MS analyses. To establish a derivatization-based LC-MS/MS method for AA, we evaluated the potential of 5-(dimethylamino)-N-(2-sulfanylethyl)naphthalene-1-sulfonamide (DNS-SH) as an effective derivatization reagent and compared its performance with that of other representative thiol reagents. The ionization efficiency, the formation of product ions during collision-induced dissociation, and the progress of the reaction-as analyzed by LC-MS (MS/MS)-were accurately evaluated based on the molar ratios determined by ¹H-qNMR. The DNS derivative of AA (AA-DNS) exhibited a superior MS response than its other thiol derivatives, providing a 4-17-fold higher MS/MS signal intensity. In addition, computational studies indicate that DNS-SH has the potential to be a more effective derivatization reagent with higher reactivity. These results indicate that analytical performance is strongly influenced by the structural characteristics of thiol reagents, particularly their ionization efficiency and product-ion formation. The newly developed analytical method was applied to quantify AA in food additives subjected to heating during manufacturing, revealing that its concentration was negligible in these samples. This finding suggests that food additives contribute minimally to overall dietary exposure to AA. Thus, the proposed method provides a highly sensitive approach for determining AA.

Moment analysis of first absolute (µ_1A) and second central (µ_2C) moments of elution peaks measured by using high-performance liquid chromatography or capillary electrophoresis is effective for extracting the information about chemical phenomena relating to their separation behavior from equilibrium and kinetic points of view. It is known that elution peak profiles should be integrated to obtain more accurate values of µ_1A and µ_2C. This means that it is required to appropriately determine the range for integrating the elution peak profiles. Our research group has used a method for determining the start and end points of the integration range. However, it seems that signal noise, baseline drift, and peak asymmetry affects the selection of the integration range and the accuracy in the determination of µ_1A and µ_2C values of elution peaks. Simulated elution peaks were prepared by adding signal noise of different intensities to a base Gaussian peak and by changing the slope of baseline. Asymmetrical peaks, i.e., tailing and leading, were also prepared by using the Exponentially Modified Gaussian function while changing the degree of asymmetry. The method was applied to choose the start and end points for integrating the simulated elution peaks. Then, the values of µ_1A and µ_2C were calculated by integrating the simulated elution peak profiles in the integration range. It was tried to clarify how the magnitude of signal noise, baseline drift, and peak asymmetry affect the selection of the integration range of elution peaks and the determination of their µ_1A and µ_2C values.