The goal of this project is to detect pollutants in real water with surface-enhanced Raman scattering (SERS). The pollutants are cyanide and chromium (VI) that were selected for last year’s project. The project targets are three folds: (1) developing new mix-type internal standard method for chromium (VI); (2) developing pretreatment procedure and quantitative analysis method for cyanide in real water samples; (3) developing method to differentiate between chromium (III) and chromium (VI) in water. For the first target, we have derived a linear relation between the ratio of the SERS signal of internal standard compound between the samples with and without chromium (VI). With this linear formula, we have determined the concentration of chromium (VI) with great accuracy, thus developing a mix-type internal standard method. For the second target, we have developed a sample pretreatment procedure for real water samples, have used the concentration curve of cyanide in water to determine the sample concentration directly, and finally have extracted the cyanide concentration by fitting the obtained data obtained from standard addition method to the nonlinear concentration formula of cyanide. For the third target, we have proved that the SERS signal of chromium (III) in water is non-recognizable and have developed a SERS method to detect it: A chelating agent is first used to form chelant with chromium (III) and the SERS method then detects the chelant. The limit-of-dection concentration of this method is below 0.05 mg/L.

Raman scattering spectroscopy, cyanide, chromium-VI