Comparative validations of non-aqueous capillary electrophoresis and high-performance liquid chromatography methods for the simultaneous determination of histamine H2 receptor antagonists in human urine

Controllable synthesis of flower-like AuNFs@ZIF-67 core-shell nanocomposites for ultrasensitive SERS detection of histamine in fish

Histamine is a significant biomarker to assess the freshness of fish products. In this study, a novel MOF-based SERS sensor for histamine determination was synthesized by wrapping PVP-capped Au nanoflowers with a ZIF-67 shell (Au NFs@ZIF-67). The highly branched Au NFs core exhibited a strong electromagnetic field enhancement effect and provided an ultra-sensitive SERS fingerprint spectrum, while ZIF-67 shell was the contributor to enrich the target and stabilize the substrate. The morphology of the core-shell structures can be easily controlled by the concentrations of the capping agent PVP and MOF precursor Co ion. Consequently, 4-MBA pre-grafted on the optimized SERS substrate can act as the Raman internal standard (IS) to eliminate signal fluctuations through standardizing all spectra against its peak at 1074 cm^-1. Moreover, as the specific receptor for histamine molecules, 4-MBA helped reach the low detection sensitivity, where the SERS intensity ratio, I₁₁₇₂/I₁₀₇₄ presented a good linear relationship towards the histamine concentrations (10^-3-10^-7 M) with the LOD of 0.87 × 10^-7 M (R² = 0.9930). Furthermore, the application in monitoring fish spoilage process demonstrated the feasibility and reliability of the developed sensor. This work provided a facile strategy to construct MOF-based SERS substrate as a potential platform for the shelf-life prediction of fish products.

Pentabromobenzyl-RP versus triazole-HILIC columns for separation of the polar basic analytes famotidine and famotidone: LC method development combined with in silico tools to follow the potential consequences of famotidine gastric instability

The competence of hydrophilic interaction (HILIC) and reversed phase liquid chromatography (RPLC) modes, employing two new stationary phases: triazole- and pentabromobenzyl-bonded silica (PBr), respectively, was inspected for separation of two polar basic analytes: famotidine (FAM) and its acidic degradant famotidone (FON). Comparison of the chromatographic efficiency, greenness, and economy aspects showed that the RPLC is superior to the HILIC. Hence, the RPLC method was adopted and validated adhering to the FDA guidelines showing excellent linearity for FAM (1.0-20.0 μg/mL) with a detection limit of 0.14 μg/mL. The method was applied to study the behavior of FAM in simulated gastric juice (SGJ), where it exhibited rapid degradation yielding FON. This degradation pathway is a probable major reason for the poor bioavailability of FAM. The kinetic study of the gastric degradation of FAM in SGJ demonstrated pseudo-first order reaction with a rate constant of 8.1 × 10^-3 min^-1. Moreover, FAM degradation has been proven to be pH-dependent and catalyzed by the gastric juice components. Hence, in situ buffered dosage form is recommended to overcome or decrease this problem. Molecular docking study shows that FON is missing a crucial stabilizing interaction with the key amino acid Asp98 causing a reduced activity at hH₂R receptor relative to FAM. Moreover, ADMET properties prediction revealed some differences in the toxicity, pharmacokinetics, metabolism, and solubility profiles of FAM and FON.

Ultrasensitive chemiluminescence assay for cimetidine detection based on the synergistic improving effect of Au nanoclusters and graphene quantum dots

A novel and sensitive chemiluminescence (CL) procedure based on the synergetic catalytic effects of gold nanoclusters (Au NCs) and graphene quantum dots (GQDs) was developed for the reliable measurement of cimetidine (CM). The initial experiments showed that the KMnO₄ -based oxidation of alkaline rhodamine B (RhoB) generated a very weak CL emission, which was intensively enhanced in the simultaneous presence of Au NCs and GQDs. CL intermediates can be adsorbed and gathered on the surface of Au NCs, becoming more stable. GQDs participate in the energy transferring processes and facilitate them. These improving effects were simultaneously obtained by adding both Au NCs and GQDs into the RhoB-KMnO₄ reaction. Consequently, the increasing effect of the Au NCs/GQDs mixture was more than that of pure Au NCs or GQDs, and a new nano-assisted powerful CL system was achieved. Furthermore, a marked quenching in the emission of the introduced CL system was observed in the presence of CM, so the system was examined to design a sensitive sensor for CM. After optimization of influencing parameters, the linear lessening in CL emission intensity of KMnO₄ -RhoB-Au NCs/GQDs was verified for CM concentrations in the range 0.8-200 ng ml^-1 . The limit of detection (3S_b /m) was 0.3 ng ml^-1 . Despite being a simple CL method, good sensitivity was obtained for CM detection with reliable results for CM determination in human urine samples.

Colorimetric sensor for cimetidine detection in human urine based on d-xylose protected gold nanoparticles

A simple, novel, and rapid colorimetric sensor for cimetidine (Cim) detection based on d-xylose protected gold nanoparticles (d-x@AuNPs) has been developed for the first time.