Boronic acid ester-based hydrogel as surface-enhanced Raman scattering substrates for separation, enrichment, hydrolysis and detection of hydrogen peroxide residue in dairy product all-in-one.

Rapid and selective separation, enrichment and detection of trace residue all-in-one in complex samples is a major challenge. Hydrogels with molecular sieve properties can selectively separate and enrich target analytes, and the combination with high sensitivity detection of surface-enhanced Raman scattering (SERS) is expected to achieve the above all-in-one detection. Herein, the core-shell structured Au@poly(N-isopropylacrylamide)-phenylboronic acid hydrogel (Au@PNIP-VBA) with boronic acid ester groups was prepared by thermally initiated polymerization. The boronic acid ester groups in hydrogel are selectively hydrolyzed by hydrogen peroxide (HO) to hydroxyl structures, leading to a reduction in SERS signals. The Au@PNIP-VBA hydrogel has molecular sieve properties and high SERS activity, making it suitable for separation, enrichment, hydrolysis and detection of HO all-in-one. A rapid SERS method was developed for analysis of HO based on the Au@PNIP-VBA hydrogel with the linear range of 8.5 × 10-6.8 mg L and the detection limit of 33 μg L. The method was successfully applied to the determination of HO residue in fresh milk, pure milk, yogurt and camel milk, with the recoveries were in the range of 82.2%-109.3% and the relative standard deviations were 2.8%-8.3%. This efficient all-in-one strategy has the advantages of simple sample pre-treatment, rapid analysis (30 min) and high sensitivity, making it highly promising for food quality and safety analysis.