Online Integration of Paper Centrifugation with SERS for Sulfanilamide Antibiotic Detections in Complex Samples: Mitigating Competitive Adsorption Interference

Surface-enhanced Raman spectroscopy (SERS) encounters difficulties in complex sample analysis due to the matrix interference caused by competitive adsorption on SERS substrates. To address this limitation, this work proposes an online-integrated paper centrifugation and SERS (PC-SERS) approach, using a circular paper disk coated with silver nanoparticles (P-AgNPs) as a separation medium and a SERS substrate. The device's functionality is enabled by the differential migration behavior of substances on the P-AgNPs disk through rotation. Upon sample loading at the disk center, centrifugal force drives radial outward diffusion of analytes, solvent, and interferents. The enhanced diffusivity of solvent molecules relative to target analytes on P-AgNPs facilitates more expeditious adsorption of the analytes onto the substrate surface, resulting in higher SERS responses in a short time. Compared with conventional SERS analysis, the PC-SERS enhances signal intensity by 14-fold within a 20 min analysis. Mechanistic studies reveal that target analytes and interferents exhibit distinct interaction forces with the P-AgNPs, causing them to deposit at separated positions on the substrate during outward diffusion, thereby forming characteristic detection zones. PC-SERS effectively resists competitive adsorption, achieving a detection limit of 1 μg·L^-1 for sulfonamide in the presence of strong interferents, which is 2 orders of magnitude lower than static SERS analysis. These enhanced capabilities enable reliable detection of trace sulfonamide antibiotics in complex matrices such as regenerated water (recovery of 84.12-105.27%) and vegetable extracts. Given the rapid analysis and portable operation requirements, PC-SERS is suggested to have strong potential for on-site environmental monitoring applications.