Facile preparation of UiO-66(Zr)-based mixed matrix membranes for thin-film solid-phase microextraction: Application to alkyl- and chlorophenols from environmental waters

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This study reports a simple strategy for integrating metal-organic frameworks (MOFs) composites in thin film solid-phase microextraction devices. In particular, the UiO-66( Zr ) MOF was successfully combined with polystyrene, forming a composite that was coated onto paper supports via dip coating. This simple strategy ensures stable mixed matrix membranes to be used as thin film microextraction coatings. Several parameters related to the preparation of the thin film devices were optimized: the paper pretreatment (evaluating the need for its conditioning), the air-drying step, the amount of MOF in the initial ink of the composite (from 0 to 60%), and the number of composite layers (from 1 to 8). These elemental features of the membranes were modified to ensure an improvement in the extraction performance for a group of target alkylphenols and chlorophenols by the microextraction strategy. It was intended not only to provide a higher enrichment factor and recovery for these target analytes, but also to improve device flexibility and stability. Optimum conditions comprise paper sheets of 2 × 1.5 cm 2 as support of the MOF composite, a paper treatment with water for 1 h, 45% ( w/w ) MOF loading in the initial ink of the composite, and 4 layers of coating. After proper characterization of the membranes, adsorption kinetic experiments from aqueous media and desorption kinetic experiments to organic solvents were developed to gain insights into their further performance for thin film microextraction. These studies demonstrated a slow adsorption rate, but 70% of the maximum adsorption capacity of the device in 60 min. This was also accompanied by a very fast desorption in methanol, requiring less than 10 min to ensure complete desorption. After the exhaustive characterization, the thin film solid-phase microextraction method in combination with high-performance liquid chromatography and diode array detection was validated for the selected application: analysis of pool and tap waters. Limits of detection as low as 21.5 μg·L −1 were achieved despite using diode array detection and considering that evaporation/reconstitution steps were not used. Besides, good inter-device and inter-batch reproducibility was achieved, with a relative standard deviation lower than 18%. The method scored 0.53, 6.53, and 65.0 in AGREEprep, SPMS, and BAGI, respectively, thus evidencing the simplicity, green character, and applicability of the methodology. • Facile preparation of MOFs-based mixed matrix membranes onto cellulose supports. • Optimum membranes have 45% w/w of the MOF UiO-66( Zr ) in the ink & 4 coating layers. • Kinetic studies indicated adequate phenols adsorption capacities & fast desorption. • MOF-based membranes are used in thin film solid-phase microextraction and HPLC-DAD. • Inter-device reproducibility in TF-SPME is <18% with great green scores – metrics.

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