In the current study, a novel monolithic capillary column functionalized with layered double hydroxide (LDH) was developed and exploited for the separation and preconcentration of fluorescent whitening agents combined with high performance liquid chromatography. Mg-Al LDH was embedded in the poly(dimethyl diallyl ammonium chloride-ethylene dimethacrylate) monolith via in situ polymerization. The ratio of LDH introduced into the polymerization mixtures was finely investigated. The characteristic properties of LDH and functionalized monolith were carefully characterized using X-ray diffraction, scanning electron microscope, Fourier-transformed infrared spectra, and thermal gravimetric analysis . After optimizing various experimental parameters, the developed method was validated and applied to the determination of fluorescent whitening agents in mask essence samples.
A novel nonenzymatic electrochemical sensor with high sensitivity for detecting organic phosphate (OPS) in medicinal herbs was fabricated based on a Mg-Al layered double hydroxide (Mg-Al LDH) nanocomposite glassy carbon electrode (GCE) modified with a poly-m-amino-benzenesulfonic acid (p-m-ABSA) film. Depositing Mg-Al LDH nanocomposites onto the surface of the p-m-ABSA composite resulted in an effective electrical response by increasing the electrode surface area and enhancing the electron transfer process, so the electrocatalytic activity was significantly enhanced. The research illustrated that the fabricated sensor (Mg-Al LDH/p-m-ABSA/GCE) exhibited strong affinity, high sensitivity, and selectivity towards methyl parathion (MP) and fenitrothion (FNT). Scanning electron microscopy (SEM) was used to characterize the surface morphology of the modified electrode and showed that the p-m-ABSA film and a few p-m-ABSA nanoparticles were coated on the surface. The surface area of the electrode was further enlarged by Mg-Al LDH owing to their layered nanostructure. Under optimal conditions, the anodic current had a linear relation equal to 0.1∼20.0 µM MP and 0.01∼50.0 µM FNT, with detection limits (S/ N = 3) of 33.0 nM MP and 3.5 nM FNT, respectively. Furthermore, Mg-Al LDH/p-m-ABSA/GCE was successfully used for the detection of MP and FNT in Astragalus and Magnolia medicinal herb samples.
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