Multivariate Optimization of an Eco-Friendly Zinc-Based MOF for Adsorptive Removal of Emerging Contaminants in Food Samples.

This work reports the development and application of a sustainable zinc-based coordination compound, [Zn-(Bz-COO)2]∞, for the detection of emerging contaminants, specifically the synthetic dyes alizarin violet (AV) and methylene blue (MB), in shrimp samples. The material was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, powder X-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller surface area analysis, and Raman spectroscopy. The extraction of contaminants was performed using multivariate optimization evaluating (i) adsorbent-to-sample ratio (1:1, 1:5, and 1:10 m/m) and (ii) eluent nature (low, medium and high polarity). As a result, the coordination compound presented a high specific surface area (5216 m2 g-1) and pore volume of 0.0136 cm3 g-1. Adsorption studies confirmed a strong affinity of [Zn-(Bz-COO)2]∞ for AV and MB, with maximum adsorption capacities of 58.583 and 20.452 mg g-1, respectively. The optimal extraction conditions involved acetonitrile for AV and ethanol for MB, with sample-to-adsorbent mass ratios of 1:5 and 1:1 (m/m), respectively, achieving recoveries higher than 80%. The adsorption kinetics followed a pseudo-second-order model, and the thermodynamic evaluation indicated a spontaneous process (ΔG ranging from -4.46 to -2.41 kJ mol-1 for MB and -4.84 to -4.46 kJ mol-1 for AV), consistent with physisorption mechanisms. Analytical validation demonstrated high sensitivity, with detection limits of 46.9 μg L-1 for AV and 4.6 μg L-1 for MB, and quantification limits of 156.3 and 15.2 μg L-1, respectively. Furthermore, the reusability evaluation showed excellent structural stability and multicycle performance, reinforcing the potential of the polymer as an environmentally friendly and low-cost solution for monitoring emerging contaminants in aquatic food products and contributing to food safety and environmental protection.