Selective-Ultratrace Detection of Metal Ions with SERS

We report the results from experiments involving the detection of metal ions with a Surface-Enhanced Raman Spectroscopic indicator (SERS indicator). Comparisons of metals showed that the SERS effect can be used to selectively detect metal ions according to their ionic radius. We determined a resolving power for separating the alkaline earth series. The results indicate that the resolving power of the SERS approach is superior to that of absorption spectroscopy. Quantitatively, under our experimental conditions, we found a detection limit of 270 ppb for Pb 2+ and 85 ppb for Cu 2+ with the indicator Eriochrome Black T.