Analytical Methods最新文献

A method for rapidly and quantitatively measuring lead (Pb) in dust has been developed. Different types of wiping materials were tested. Due to its adhesive properties and flatness when folded, painter's tape effectively picks up dust and, when coupled with portable X-ray fluorescence (XRF) provides a rapid and sensitive measurement of Pb in dust. The tape can pick up approximately 0.095 g of dust, which is comparable to the amount of dust present in one square foot of a house that is vacuumed once a month (0.100 g). Dust in an area of 1 square foot was wiped up and a calibration curve was constructed by analyzing the folded tape on XRF (in ppm) versus the amount of Pb on the wipe that was determined by digestion and ICP-OES (in µg). Validation of this method revealed that when tested at each of the current EPA action levels for Pb dust (5 µg for floors, 40 µg for windowsills and 100 µg for window troughs), each of the false positive rates (FPR) was below 15% and each of the false negative rates (FNR) was below 5%. Thus, at these lower Pb levels, Painter's tape with XRF measurement could allow for spatially-resolved, rapid determination of Pb in dust on site, which has been a long-standing need.

The confinement effect of silica nanoparticles (SNPs) can significantly enhance the fluorescence and sensing performance of metal nanoclusters. In this study, silver nanoclusters (Ag NCs) were encapsulated within silica nanoparticles (SNPs) via a reverse microemulsion method to form a silver nanoclusters/silica nanoparticles (Ag NCs/SNPs) composite. The composite exhibited superior fluorescence properties compared to bare Ag NCs. It was found that cefixime (Cfx) could effectively quench the fluorescence of Ag NCs/SNPs (λ_ex = 265 nm; λ_em = 298 nm). Based on this, a novel fluorescence method was developed for the detection of Cfx. Under optimal conditions, the probe showed a linear response to Cfx concentrations ranging from 0.77 to 24.4 µmol L⁻¹, with a limit of detection (LOD) of 0.37 µmol L⁻¹ (LOQ = 1.23 µmol L⁻¹). The method demonstrates high selectivity for Cfx against common interferents. When applied to the analysis of pharmaceutical samples and human serum sample, the method yielded satisfactory recovery rates of 92.57–109.83% and 93.73–102.05%, respectively, with relative standard deviations (RSD) below 6.51%. These results confirm that the proposed sensing system is robust and reliable, indicating its great potential for application in pharmaceutical quality control and the detection of Cfx in biological samples.

Orthodontic treatment involves the use of braces and clear aligners to correct the misalignment of teeth and jaws, thus enhancing functionality, aesthetics and overall dental health. The significant drawback of this treatment is its lengthy duration. Caffeine and misoprostol have exhibited the potential to enhance orthodontic tooth movement and decrease treatment time. However, no combined formulation of these two agents is currently available and a validated method for their simultaneous estimation has not been yet established. To address this gap, our research group is actively working on developing a novel formulation incorporating both caffeine and misoprostol for orthodontic applications. As a critical first step toward this goal the present study focuses on employing the AQbD approach using a Box–Behnken design for the simultaneous estimation of caffeine and misoprostol. The optimized mobile phase consisted of acetonitrile, HPLC-grade water and 1.25 × 10⁻⁴ M orthophosphoric acid solution in a ratio of 69.5 : 30 : 0.5 (v/v/v). Key parameters of the method were optimized, which included a flow rate of 0.9 ml min⁻¹, an injection volume of 20 µl and a column temperature of 40 °C. Under these chromatographic conditions the retention times for caffeine and misoprostol were 2.8 and 4.9 minutes, respectively, with both exhibiting an acceptable tailing factor of 1.1. Calibration plots demonstrated excellent linearity for both compounds. The method's sensitivity was assessed with the LOD and LOQ determined to be 0.51 µg ml⁻¹ and 1.57 µg ml⁻¹ for caffeine and 0.40 µg ml⁻¹ and 1.23 µg ml⁻¹ for misoprostol, respectively. The method was then validated according to ICH Q2(R2) guidelines. Also, the quantitative analysis of lab developed nanoparticles demonstrated a recovery of no less than 98% with a relative standard deviation (RSD) of no more than 2%. This validated method provides a reliable analytical approach for the simultaneous estimation of caffeine and misoprostol in pharmaceutical formulations, thereby strengthening quality control in orthodontic treatment formulations.

Metal–organic gels (MOGs) are a class of dynamic three-dimensional soft materials formed by the self-assembly of metal ions or clusters with organic ligands under mild conditions. Owing to their tunable porous structures, abundant active sites, exceptional optical properties, and enhanced environmental stability, MOGs have emerged as promising candidates for fluorescence sensing applications. This review presents a systematic overview of recent advancements in MOG-based fluorescence sensing, which is structured around the logical framework of “properties-design-mechanism-application”. It covers key aspects including the fundamental fluorescent properties of MOGs, rational design strategies for optimizing sensing performance, core fluorescence sensing mechanisms, and representative applications in the fields of environmental monitoring, food safety detection, and biomedical analysis. Finally, critical challenges and future perspectives in this rapidly evolving field are discussed, aiming to provide guidance for further research directions.

Carbendazim is a broad-spectrum fungicide that is effective in controlling diseases caused by fungi (e.g., adenomycetes and polybacteriums) in crops. It is known that carbendazim is persistent and toxic to mammals, and has always been a carcinogen for humans. However, various carbendazim pesticide formulations are still allowed to be produced and used in crop farming. In this work, we used state-of-the-art vacuum ultraviolet (VUV, 118 nm) single-photon postionization mass spectrometry imaging to detect traces of pesticide carbendazim on the paraxial surface of growing plant leaves, and to explore the absorption and in situ distribution of pesticide carbendazim on the leaf surface. Compared to other mass spectrometry imaging methods, this method can achieve rapid detection with simple operation and requires no sample preparation. The results indicate that the limit of detection (LOD) of the proposed method is estimated to be ca. 50 pg per sampling spot. Additionally, we investigated the residues and distribution of pesticide carbendazim on plant leaves by visualizing the distribution of carbendazim on leaf surfaces to locate pesticide residues. The results of this study showed that the vacuum ultraviolet (VUV) single-photon postionization MSI method could be used to determine the quality of pesticide residues on the surface of plant leaves, which was of great significance for the hygienic detection of herbs, fruits, and vegetables.

In this study, nitrogen-doped mesoporous carbon (NMC) was synthesized using Zn-MOF-8 as a template, followed by further reaction with multi-walled carbon nanotubes (MWCNTs) to prepare the NMC/MWCNTs nanocomposite. Characterization of the composite was performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electrochemical methods. The NMC/MWCNTs/GCE developed from this nanocomposite achieved highly sensitive and stable detection of IQ. On the surface of NMC/MWCNTs electrodes, the hydroxyl groups at the 3′- and 4′-positions of the C ring in the isoquercitrin (IQ) structure are oxidized to 2-quinone while losing two hydrogen atoms, demonstrating the modified electrode's outstanding catalytic oxidation performance. The GCE modified with the NMC/MWCNTs composite at a concentration of 0.6 mg mL⁻¹ exhibited a broad linear range of 0.1–65 µM for IQ detection in PBS buffer solution at pH 6.5, with a detection limit of 0.087 µM (signal-to-noise ratio of 3). The electrochemical method for IQ detection demonstrated advantages including convenience, high sensitivity, and low cost. Furthermore, the sensor was evaluated for stability, repeatability, and interference resistance, and applied to IQ detection in real samples.

In view of the importance and urgency of elucidating the internal exposure toxicity and transport mechanisms of nanoplastics (NPl) in organisms for assessing their health risks, we developed a novel analytical method that integrates online preconcentration via a sodium dodecyl sulfate (SDS)-functionalized regenerated cellulose membrane (RCM) with separation and detection using an asymmetric-flow field-flow fractionation system coupled in-line to a diode array detector and a multi-angle light scattering detector (AF4-DAD-MALS system) for the quantification of 60–500 nm NPl in biological matrices. This method boasts high accuracy (recovery: 89–103%), precision (RSD < 5.2%), sensitivity (LOD: 0.5–2.0 µg L⁻¹) and reusability. The method was applied to study the blood circulation of polydisperse NPl. The results showed that larger particles had a prolonged circulation time.

The human papillomavirus (HPV) causes most cervical cancer cases. Although cervical cancer is the fourth most common cancer among women globally and has a high mortality rate, it remains the most treatable cancer upon early detection. Compared with HPV DNA tests, HPV mRNA testing is a more effective detection method, as it determines the presence of active oncogenic transcripts. This study presents findings as a proof-of-concept of a multimodal detection biosensor for detecting HPV 16/35 E6 transcripts using a branched hybridization chain reaction (bHCR)-amplification method. Branched HCR hairpins amplified the short RNA targets into long DNA concatemers verified using gel electrophoresis and fluorescence readouts. The bHCR system achieved a lowest detection concentration at 0.125 µM. There was no cross-reactivity with other HPV subtypes (HPV 18, 58, 51, 31, 73, 52, 66, 58, 42, 82, 54, 70 and 44). To further demonstrate the multimodal applicability, bHCR products were evaluated using Cas13a collateral activity and non-enzymatic direct visualization using biotin-labeled hairpins. Lateral flow strips qualitatively confirmed the assay's performance at reducing initiator target concentrations consistent with the fluorescence measurements. Combination of the fluorescence readouts with the complementary visual readouts demonstrates the potential flexibility of the bHCR assay for laboratory and point-of-care settings. The bHCR assay presents a versatile diagnostic strategy for detection of HPV 16/35 oncogenic transcripts while offering a customizable platform for adaptation to other molecular biomarkers.

Wood moisture content critically influences the performance and processing quality of wood-based panels. Therefore, precise and rapid prediction of wood moisture content is essential for enhancing production efficiency and ensuring product quality. In this study, three representative wood raw materials for wood-based panels (Tilia, Larix, and Picea) were investigated. Their near-infrared spectral (NIRS) data were collected, and anomalous samples were identified and removed. The spectral data were then pre-processed, and the Competitive Adaptive Reweighted Sampling (CARS) algorithm was applied to extract features highly correlated with wood moisture content. Subsequently, Partial Least Squares (PLS) regression, Convolutional Neural Network (CNN), CNN combined with channel attention mechanism (CNN-CAM), CNN combined with spatial attention mechanism (CNN-SAM), and CNN combined with Convolutional Block Attention Mechanism (CNN-CBAM) models were developed and evaluated for their suitability and stability in predicting wood moisture content. A total of 305 wood-based panel material samples were randomly divided into calibration and prediction sets at a 3 : 1 ratio. The samples underwent outlier removal, spectral preprocessing, feature extraction, and modeling. Among all methods tested, the CNN-CBAM model combined with CARS-based feature selection achieved the highest accuracy, yielding a prediction set coefficient of determination (R²) of 0.9730 and a root-mean-square error of prediction (RMSEP) of 0.1840. The CNN-CBAM model demonstrates excellent performance in predicting the moisture content of Tilia, Larix, and Picea used in wood-based panels. By incorporating the convolutional block attention mechanism, the model effectively captures key spectral features, accounting for both global inter-channel correlations and local spatial distinctions. This significantly enhances prediction accuracy and generalization, providing an efficient tool for online monitoring and quality control in the production of wood-based panels.

Kelvin Probe Force Microscopy (KPFM) has emerged as a valuable tool in biological sciences by providing direct access to the nanoscale electrical landscape of living systems. This technology uniquely bridges a critical gap in biophysical characterization, enabling the noninvasive, label free mapping of surface potential distributions with nanoscale resolution under physiological conditions. The ability to directly correlate electrical properties with topographical and mechanical information across diverse biological interfaces, from cell membranes and proteins to biomaterials and extracellular vesicles, is revolutionizing our understanding of life's fundamental processes. This review comprehensively examines the principles, advancements, and far reaching applications of KPFM, highlighting how it reveals structure function relationships in biomolecules, quantifies drug induced cellular responses, guides the rational design of advanced biomaterials, and identifies novel disease biomarkers. Key technological innovations such as high speed and multimodal KPFM are overcoming traditional limitations, allowing dynamic monitoring of biological events and integration with complementary techniques. While challenges in absolute quantification and imaging speed persist, ongoing developments in probe technology, liquid phase operation, and data analysis are poised to further solidify KPFM's role. The insights driven by KPFM not only deepen our fundamental knowledge of electrophysiological mechanisms but also pave the way for groundbreaking advancements in biomedical engineering, targeted therapeutic development, and next generation diagnostic technologies, ultimately shaping the future of precision medicine.