Thin-film microextraction coupled to surface enhanced Raman scattering for the rapid detection of benzoic acid in carbonated beverages

Benzoic acid (BA) is widely used as an antimicrobial preservative in carbonated beverages. In this study, silica gel thin-film microextraction (TFME) coupled to surface enhanced Raman scattering (SERS) was applied for the rapid detection of BA in carbonated beverages. The TFME process was performed by placing small pieces of silica gel substrate in a simple homemade device, and then the content of BA was detected using SERS after colloidal gold was uniformly dropped onto the substrate. The obtained SERS signals of BA were strong and of high reproducibility. A good linearity between the concentration of BA and the SERS signal intensity at 994 cm(-1) in the range of 25-500 pg mL(-1) was obtained under optimal experimental conditions. The detection limit value was found to be 3.6 pg mL(-1) and the recovery of the spiked BA was in the range 85.0-103.0%. The developed method was successfully applied to detect BA in carbonated beverage samples as the results were consistent with those using high performance liquid chromatography, suggesting that it is a rapid, convenient and sensitive way to achieve BA detection in carbonated beverages.