Analytical Methods最新文献

Liquid crystal monomers (LCMs) are emerging organic pollutants to which humans are chronically exposed at low doses. Accurate quantification of LCMs in biological matrices remains challenging due to their low environmental concentrations and significant matrix effects. By optimizing the GC-MS conditions and the sample pretreatment process, this study developed a novel approach for robust determination of three LCMs including 2,3-difluoro-4-(trans-4-propylcyclohexyl) butoxybenzene (3cH4OdFP), 4-propoxy-4′-cyanobiphenyl (3OCB), and 4-ethyl-4′-(4-propylcyclohexyl)-1,1′-biphenyl (3cH2B) in mouse serum, brain, heart, liver, spleen, lung, and kidney tissues. Serum samples were extracted with n-hexane, while tissues were extracted using acidified acetonitrile followed by QuEChERS cleanup. Separation was achieved on a DB-17HT column, and detection was performed in selected ion monitoring (SIM) mode of GC-MS. The method demonstrated good linearity (r² > 0.995) from 0.5 ng mL⁻¹ to 200 ng mL⁻¹. Limits of detection were 0.2 ng g⁻¹ for tissues and 1.0 ng mL⁻¹ for serum. Average recoveries ranged from 74.32% to 126.04%, with intra-day and inter-day precision in the range 2.17–18.53% and 3.75–19.13%, respectively. The validated method was successfully applied to exposed mice, revealing widespread tissue distribution of the three LCMs. The concentration ranges in serum and tissues were as follows: 3cH4OdFP (Not Detected (ND)–6.1978 µg g⁻¹), 3OCB (ND–30.1073 µg g⁻¹), and 3cH2B (ND–67.3851 µg g⁻¹). The spleen exhibited a higher accumulation potential. This sensitive and reliable method provides a robust tool for monitoring LCMs in toxicological research and assessing internal exposure, while also revealing their potential immunotoxicity.

Addressing the challenges of strong matrix interference, cumbersome procedures, and urgent demand for on-site rapid detection in the analysis of tetracycline antibiotic (TCA) residues in milk, this study aims to develop an efficient, rapid screening method based on the amplified luminescence proximity homogeneous assay (AlphaLICA) technology for the direct detection of tetracycline (TC) and other TCA residues in milk. By conjugating TC–BSA complexes to receptor microspheres and goat anti-mouse IgG antibodies to donor microspheres, this approach effectively overcomes interference from milk fat and casein, enabling wash-free, homogeneous detection. This method exhibits high sensitivity (limit of detection (LOD): 0.16 ng mL⁻¹; limit of quantification (LOQ): 0.83 ng mL⁻¹), with a linear range of 0.83–32 ng mL⁻¹. Spiked recovery rates reached 100.95–114.78% (relative standard deviation (RSD) ≤ 8%), while intra- and inter-batch coefficients of variation (CV) ranged from 3.89%–13.24% and 4.34–13.52%, respectively. Cross-reactivity with non-TC antibiotics remained low (CR ≤ 10.68%). Compared to the traditional enzyme-linked immunosorbent assay (ELISA, 75 minutes, requiring washing), this method requires only 10 minutes and is wash-free. The results of actual sample testing showed high consistency with the reference method (Y = 0.7685X + 0.4623, r² = 0.952, p < 0.001). This study provides a reliable technical solution for high-throughput rapid field monitoring of TCA residues in milk.

Paraquat is a highly polar herbicide that can be detected in environmental water samples due to its unauthorized use in agriculture and its high mobility in aquatic systems. Its determination at trace levels remains analytically challenging, particularly when using conventional multiresidue methods based on reversed-phase liquid chromatography, which often requires ion-pairing reagents that compromise the method precision. In this work, the application of a large-volume injection (LVI) strategy was exploited for a superficially porous (core–shell) column to enhance the sensitivity of paraquat detection in tap water samples using HPLC with UV detection at 257 nm. The hydrophilic interaction liquid chromatography (HILIC) enabled paraquat retention, with a mobile phase composed of 50 mmol L⁻¹ ammonium formate (pH 3,0) and acetonitrile (25 : 75, v/v). The method employed an injection volume of 50 µL and provided robust quantification of paraquat in tap water, achieving a limit of quantification of 2.5 µg L⁻¹, excellent linearity (R² = 0.9999), and recovery values between 98.3 and 107.0%, without matrix effects. The strategy crucially avoided SPE preconcentration and waste generation. The proposed method circumvented the sample volume limitations typically associated with core–shell columns, achieving a simple and cost-effective approach for paraquat environmental monitoring.

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.