Characterization of the Ag mediated surface-enhanced Raman spectroscopy of saxitoxin

The rapid detection and quantification of saxitoxin (STX) is reported using surface-enhanced Raman spectroscopy (SERS) with a colloidal hydrosol of silver nanoparticles. Under the conditions of our experiments, the limit of detection (LD) for STX using SERS is 3 nM, with a limit of quantification (LQ) of 20 nM. It is shown that the SERS method is rapid, with spectra being collected in as little as 5 seconds total integration time for a 40 nM STX sample. In order to improve the signal-to-noise ratio, SERS spectra were generally collected with a total integration time of 1 minute (6 accumulations of 10 seconds each), with no need for extensive sample work-up or substrate preparation. Based on these results, the SERS technique shows great promise for the future detection and quantification of STX molecules in aqueous solutions.