Determination of Bisphenol A in Beverages by SERS Using Solid-Phase Extraction and in Situ Synthesis of Silver...

A highly sensitive method has been developed for the determination of bisphenol A (BPA) in beverages (juice, beer, carbonated soft drinks) using surface-enhanced Raman spectroscopy (SERS) coupled with solid-phase extraction (SPE), in situ synthesis of silver nanoparticles (AgNPs), and surface modification with tetraoctylammonium bromide (TNOAB). SPE showed high BPA recovery rates (>90%) from complex food matrices. The crucial factor for achieving maximum sensitivity was the in situ synthesis of AgNPs directly in the presence of the analyte, as the use of pre-synthesized nanoparticles led to an approximately 100-fold decrease in signal intensity. Investigation of cationic modifiers with different structures revealed that the efficiency of SERS signal enhancement correlates with alkyl chain length. TNOAB (C8) provided a 7-fold increase in signal compared to the unmodified system, significantly outperforming the effects of tetrabutylammonium bromide (C4, 1.7-fold enhancement) and triethylamine (C2, 1.3-fold enhancement). The limit of detection for BPA was 0.077 ppb with a signal enhancement factor of 1.87 × 10⁸. For quantitative analysis, a PLS calibration model was applied in the range of 1-100 ppb (R² = 0.9986, RMSEC = 1.75 ppb, RMSEP = 1.95 ppb). The simplicity of the developed approach makes it suitable for routine monitoring of BPA content in beverages.