Synergistic azo reaction and electroextraction in SPME-SERS for direct determination of aromatic amines in biofluids...

A solid-phase microextraction-SERS (SPME-SERS) analysis system was enhanced by the synergistic integration of azo reaction and electroextraction (Azo/EEx/SPME-SERS) to directly determine aromatic amines in serum and urine. Azo reactions selectively converted aromatic amines (e.g., aniline) into positively charged derivatives, which were selectively absorbed onto a rough silver SERS substrate via charge-selective electroextraction (- 0.2 V), excluding anionic interferents. Electroextraction-accelerated mass transfer and real-time SERS detection enabled rapid preconcentration and spectral acquisition under 3 min. The azo reaction increased the Raman scattering cross-section of aniline, and electroextraction reduced the distance of azo aniline to the SERS hot spots. This enabled low detection limits (aniline, 0.005 µg·mL^-1). The Azo/EEx/SPME-SERS method achieved dual-dimensional interference exclusion through chemical derivatization (azo reaction) and physical charge-selective electroextraction, granting aromatic amines competitive adsorption advantage over serum metabolites at SERS hotspots. This synergy allows for the direct detemination of aniline in urine/serum with only 5-10 fold dilutions. It avoids the need for tedious pretreatments, while maintaining recoveries of 92-107%, accuracy of 97.33% (urine) and 94.89% (serum), and method detection limits of 0.05 µg·mL^-1 (urine) and 0.5 µg·mL^-1 (serum).