In situ screening of sodium sulfite residue on edible mushroom using SERS active paper swab

In the present study, a printing paper functionalized with Ag nanoparticles (AgNPs) was used as a flexible surface-enhanced Raman spectroscopy (SERS) swab (AgNP@FP) to evaluate its ability to detect sodium sulfite residues on the surface of edible mushrooms. The results showed that the prepared AgNP@FP swab had fingerprint-like signals (at 620 and 927 cm(-1)), which could serve as a clear confirmation of the analyte. In addition, the swab not only exhibited good repeatability, with spot-to-spot variation of < 2.6% at 620 cm(-1) signal intensity, but it also met the requirement of commercial transportation as the peak intensity at 620 cm(-1) remained at 57.84% of its initial value after 5 days of storage. The sensitivity of the substrate to sodium sulfite on the surface of oyster mushroom and enoki mushroom was as low as 0.2 mg/mL. The limit of detection (LOD) values of the sulfite residue on the surface of oyster and enoki mushrooms were 1.2 and 1.6 mg/kg, respectively. This study demonstrated that the AgNP@FP swab provided a simple tool for obscure and in situ screening of residues on the surface of agricultural products.