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A magnetic hydrogel based on xylan (X), poly (acrylic acid), and maghemite (γ-Fe 2 O 3 ) named HXA-Fe 2 O 3 was synthesized, characterized, and applied as an alternative material to remove methylene blue (MB) from aqueous media by adsorption. Maghemite was synthesized by coprecipitation method and later incorporated in the hydrogel matrix synthesized by free radical polymerization. The characterization studies included FTIR, DSC, XRD, VSM, Zeta Potential, TGA, SEM, TEM, and N 2 adsorption isotherms (BET). The physicochemical characterization results confirmed the intended synthesis and showed the compositional, thermal, structural, morphological, textural, and magnetic profile of the materials. The adsorption studies included experimental design, kinetic, and isotherm. A full factorial design was employed considering the factors adsorbent dosage (g L -1 ), pH, and ionic strength (mmol L -1 of NaCl) for adsorption capacity and removal percentage responses. As ionic strength was not significant, a Doehlert design was employed with adsorbent dosage and pH, indicating the optimal adsorption conditions. The kinetics was well described by the PSO model, while the isotherm obeyed the Sips model. Equilibrium was attained at 60 min, and the maximum experimental adsorption capacity was up to 250.26 mg g -1 at pH 8.5, adsorbent dosage of 0.2 g L - 1 , and 298 K. These findings show that the magnetic hydrogel produced has great potential to be applied in the adsorption of basic molecules, such as MB., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Enzyme assays can be performed with the capillary electrophoresis technique (CE) in many approaches, such as the immobilized enzyme micro-reactor. Acetylcholinesterase is a promising enzyme to be used when pursuing such a method, as it has already been explored in the proposal of similar methods of miniaturizing enzyme assays. The present work proposes a novel enzyme micro-reactor, based on the anchorage of the enzyme on magnetic nanoparticles of MnFe 2 O 4, with chitosan and glutaraldehyde as the cross-linker in the capillary by means of an arrange of neodymium magnets. The calculated K m of the enzyme evaluated by this method was 1.12 mmol L -1 , comparable to other studies in the literature that utilizes immobilized enzymes. Also, IC 50 for neostigmine was assessed in 3 different micro-reactors, with an average of 29.42 ± 3.88 μmol L -1 . In terms of the micro-reactor stability, it was possible to perform at least 25 experiments with assembled micro-reactor. The method was applied to hydroalcoholic extracts of 7 plant species. Plinia cauliflora had the best result, with 42.31 ± 6.81% of enzyme inhibition in a concentration of 100 mg L -1 ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)