A heat-assisted array gas membrane separation strategy coupled with High-Performance Liquid Chromatography Fluorescence detection was developed for sensitive determination of metformin based on an indirect quantification principle. Metformin was converted in situ under alkaline heating into volatile dimethylamine (DMA), which was selectively transferred through a hydrophobic PTFE membrane and trapped in an acidic acceptor solution, followed by pre-column derivatization with dansyl chloride to enable fluorescence detection. Mechanistic investigations confirmed DMA formation and identified additional alkaline degradation products (guanylurea-type intermediate, urea and guanidine) by HILIC and High-Resolution Time-of-Flight Mass Spectrometry, providing the chemical basis for the indirect workflow. Computational fluid dynamics simulations indicated focused headspace flow across the membrane (57.6% of total flow), negligible trans-membrane pressure (<0.5 Pa) and a moderated membrane temperature (∼49°C) under an 80°C heat source, rationalizing efficient transfer and reduced secondary volatilization. Key parameters were optimized, including heating time, absorption configuration, derivatization conditions. Under optimized conditions, the method was linear over 20-100 μg/mL (R=0.9924) with a limit of detectionof 0.002 μg/mL (S/N=3). Applicability was demonstrated in corn silk tea and sour jujube kernel tea, giving recoveries of 89.2-99.3% at 100 μg/mL and 95.4–102.0% across spiking levels, with no evident chromatographic interferences. The Alkaline Hydrolysis-Array Gas Membrane Separation-HPLC-FL approach integrates conversion, membrane-based separation and fluorescence derivatization, offering an efficient and solvent-minimized option for routine screening of metformin adulteration in complex matrices.
An electrochemical sensor based on environmentally friendly eRAFT polymerization was developed for the detection of aflatoxin B 1 (AFB 1 ) in food and herbal medicine. Two biological probes, aptamer (Ap) and antibody (Ab), were used to specifically recognize AFB 1 , and a large number of ferrocene polymers were grafted on the electrode surface by eRAFT polymerization, which greatly improved the specificity and sensitivity of the sensor. The detection limit of AFB 1 was 37.34 fg/mL. In addition, the recovery rate was 95.69% to 107.65% and the RSD was 0.84% to 4.92% by detecting 9 spiked samples. The delighted reliability of this method was verified by HPLC-FL.
A novel fluorescence labeling reagent N-acetylhydrazine acridone (AHAD) was designed and synthesized. A highly sensitive high performance liquid chromatography (HPLC) method coupled with fluorescence detection to determine benzaldehyde after derivatization with AHAD was developed. Optimum derivatization was obtained at 40 °C for 30 min with trichloroacetic acid as catalyst. Benzaldehyde derivative was separated on a reversed-phase SB-C18 column in conjunction with a gradient elution and detected by fluorescence detection at excitation and emission wavelengths of 371 nm and 421 nm. The established method exhibited excellent linearity over the injected amount of benzaldehyde of 0.003 to 5 nmol mL−1. The method was successfully applied to the determination of serum semicarbazide-sensitive amine oxidase (SSAO) activity in humans. SSAO is a significant biomarker because serum SSAO activity is elevated in patients with Alzheimer's disease, vascular disorders, heart disease and diabetes mellitus. It was demonstrated that the SSAO activity of the hyperglycemic group (60 ± 4 nmol mL−1 h−1) was significantly higher than that of normal blood sugar group (44 ± 4 nmol mL−1 h−1) with P < 0.05.
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