The quality characteristics of wine were strongly influenced by mercaptans, which were key flavor substances contributing to the characteristic aroma profile of wines. Although the wide usages of chromatography and mass spectrography in mercaptan analysis, the complex sample pretreatment and time-consuming analysis processes limited their application in rapid detection. In this work, the rapid sensing method of cyclic cataluminescence (CCTL) was extended to mercaptan analysis by introducing La2O3 as a catalyst, and a dynamic response strategy for wine discrimination was established. The La2O3 catalyst was synthesized by a simple hydrothermal method and possessed a layered structure and exhibited excellent catalytic activity toward the luminescence reaction of mercaptan substances. The characteristic attenuation coefficient (k) was derived by fitting the decay of peak intensity of the CCTL curve over time. The obtained k values were found to depend on both the concentration and composition of the composite sample. The CCTL method was successfully applied to 55 wine samples, including 12 different wine brands from various production areas. Each wine brand exhibited a characteristic k value, while the same brand showed high consistency. Furthermore, when combined with linear discriminant analysis (LDA) and hierarchical cluster analysis (HCA), the method achieved 100
A novel core-shell structured boronic acid–functionalized covalent organic framework composite (SiO2@COF-PBA) was designed for the selective extraction of monoamine neurotransmitters (MNTs). The material was synthesized via a Schiff base reaction between 2,5-divinylbenzene-1,4-dicarbaldehyde (DD) and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAT) on the SiO2-NH2 surface, followed by covalent grafting of 4-mercaptophenylboronic acid (4-MPBA) through thiol-ene click chemistry. The resulting SiO2@COF-PBA exhibited uniform spherical morphology, high specific surface area, and excellent chemical stability. Owing to the specific boronate affinity toward cis-diol moieties, the material demonstrated high adsorption capacity and favorable selectivity for MNTs compared with commercial adsorbents. The adsorption isotherms and kinetics of the four MNTs were systematically investigated. An online solid-phase extraction method coupled with high-performance liquid chromatography-fluorescence detection (online SPE-HPLC-FLD) was established using the SiO2@COF-PBA packed column. The parameters influencing the online extraction efficiency, including the pH of the sample solution, the extraction and desorption flow rates, and the desorption volume, were investigated. Under optimized conditions, the enrichment factors for the four MNTs reached 37–225. The developed method exhibited wide linear ranges (0.10–100.0 ng mL−1, R2 ≥ 0.9991), low limits of detection (0.035–0.054 ng mL−1), and good precision (RSDs of 1.7–4.8
A solid-phase sorption–spectrophotometric procedure was developed for the determination of Ni(II) in natural waters using nitrazine yellow (NY) immobilised on PPA-1, an anion-exchange fibre obtained by treating hydroxylamine-activated polyacrylonitrile with polyethylene polyamine. Reagent immobilisation and Ni(II) binding were characterised by absorption and diffuse-reflectance spectroscopy, Raman spectroscopy, conductometry and scanning electron microscopy with energy-dispersive X-ray analysis (SEM–EDS). In aqueous solution, the absorption maximum of NY shifts from 465 to 583 nm on complexation with Ni(II) (Δλ = 118 nm), whereas on the fibre the Kubelka–Munk maximum shifts from 470 to 620 nm (Δλ = 150 nm), so that the analytical signal is measured where the reagent-loaded blank absorbs only weakly. For the solid-phase determination (50 mL sample, pH 6.4, 0.2000 g of NY-loaded fibre, 10 min contact time, no free reagent added), ΔF(R) at 620 nm was linear in the mass of Ni(II) over 4.2–88.5 µg per 50 mL (84–1770 µg L−1; R2 = 0.9985, ten levels, four replicates each). The limits of detection and quantification (3sy/x/b and 10sy/x/b) were 72 and 240 µg L−1, and the repeatability was 0.1–0.9
Selective regulation and reliable monitoring of intracellular H2O2/O2 homeostasis are important for understanding cellular redox processes, yet multifunctional nanozymes often exhibit competing enzyme-like activities that complicate their catalytic behavior under biologically relevant conditions. Herein, we developed a pH-responsive mesoporous platinum/ferrous ion (mPt/Fe2+) nanozyme with switchable oxidase-like (OXD-like), peroxidase-like (POD-like), and catalase-like (CAT-like) activities. Systematic catalytic characterization revealed distinct pH-dependent activity profiles, with the maximum OXD-like, POD-like, and CAT-like activities occurring at pH 3.0, 4.5, and 6.5, respectively. Notably, at pH 6.5, the OXD- and POD-like activities were strongly suppressed, whereas CAT-like activity predominated, enabling efficient decomposition of H2O2 into O2 with reduced interference from competing catalytic pathways. Compared with pristine mPt, mPt/Fe2+ exhibited enhanced catalytic performance and a relatively high affinity toward H2O2. Kinetic analyses further demonstrated favorable substrate interactions and catalytic efficiency. Mechanistic studies using reactive oxygen species-responsive fluorescent probes revealed that 1O2 and •OH were involved in the POD-like pathway, whereas O2 participated in the CAT-like pathway. Density functional theory calculations showed that Fe2+ incorporation strengthened H2O2 adsorption and decreased the key free-energy barriers for H2O2 decomposition, providing a molecular basis for the enhanced CAT-like activity. Furthermore, RDPP- and DCFH-DA-based fluorescence assays combined with confocal laser scanning microscopy demonstrated concentration-dependent intracellular O2 generation and H2O2 depletion in tumor cells. This work establishes a pH-responsive nanozyme platform integrating catalytic switching, mechanistic analysis, and intracellular fluorescence imaging, offering a useful analytical strategy for probing and regulating cellular H2O2/O2 homeostasis.
Untargeted metabolomics often requires separate positive and negative ionization mode injections to maximize metabolome coverage, increasing analytical time, analysis cost, and complexity. Polarity switching (PSW) represents a promising alternative, yet its adoption in untargeted metabolomics remains limited, likely due to the lack of systematic performance evaluations as well as lack of polarity-switching capability on some mass spectrometers. In this study, we compared the performance of the PSW method to that of separate polarity injections by assessing the total number of detected features, the total number of metabolite annotations, Level 1 and 2 annotations, statistical analysis outcomes, and functional enrichment analysis results. Overall, separate polarity acquisition yielded the highest number of total detected features and annotations. Despite these differences, a strong overlap was observed at higher annotation confidence levels, with 70–76
