Abstract: In this work, a surface-enhanced Raman scattering (SERS) chip based on 4-mercaptoboric acid (4-MPBA) probe was developed by controllable self-assembly for the ultrasensitive quantitation of SO32-. This technique was based on the oxidative transformation of SO32- to SO42- and the Lewis acid-base coordination principle. The quantitative detection of SO32- was based on the ratio of the intensity of the peak at 1 382 cm-1 to that at 1 070 cm-1 (I1 382/I1 070). This ratiometric quantification strategy avoided errors caused by the inhomogeneity of SERS substrates, and effectively improved the reliability of detection signals. The limit of detection (LOD) of this SERS chip was as low as 5 × 10-8 mol/L, and a good linear relationship was obtained over the concentration range of 5 × 10-8 –1 × 10-3 mol/L (R2 = 0.997 4). Using this method, the SO32- content in white sugar was determined to be 1.42 mg/kg and recoveries for spiked white sugar were 98.38%–107.82%, suggesting that this method has good application prospects for the rapid determination of trace levels of SO32- in actual samples.

Key words: surface-enhanced Raman scattering; sulfite; Lewis acid-base theory; 4-mercaptoboric acid; quantitative detection