Accurate in-field quantification of antioxidants in food is essential for straightforward assessment of nutritional value. To this purpose, a MIP-based colorimetric assay based on the strong chromogenic complexation between the natural antioxidant sinapic acid and Cu(II) for direct detection in food samples was developed. MIPs were synthesized based on a bio-based DES-modified monomer and their specificity (IF = 2.61), composition, particle size distribution and thermal stability characterized. MIPs were integrated into colorimetric assay based on the displacement of visible sinapic acid-Cu(II) complex. The response was optimized considering target binding kinetics, polymer mass, complexation time and pH. The optimized assay demonstrates high sensitivity with LOD of 0.33 and 0.72 μM by UV–Vis and smartphone respectively, dual linear ranges and outstanding selectivity against structural analogues. Quantification of sinapic acid in mustard seeds correlated strongly with LC-MS results with recoveries ranging from 99.0 to 111.3%, underscoring the method's real-world applicability. • DES integration into MIPs consistently improves performance. • Smartphone detection enables direct in field antioxidant sensing. • Exceptional selectivity results from combination of MIP and metal-complex properties. • Displacing natural antioxidant-metal complexes holds substantial untapped potential.
Wissen et al. (Sun,) studied this question.