Surface-Enhanced Raman Detection of Aqueous Cyanide

Author： Shelton Robert D. Haas John W. Wachter Eric A.

Publisher： Society for Applied Spectroscopy

ISSN： 0003-7028

Source： Applied Spectroscopy, Vol.48, Iss.8, 1994-08, pp. : 1007-1010

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Abstract

Cyanide ion (CN^-) has been the subject of numerous studies probing the mechanisms underlying the surface-enhanced Raman scattering (SERS) phenomenon. This work examines various aspects critical to application of SERS for direct detection of trace cyanide in groundwater and in wastewater streams. A new method for direct quantitation of cyanide in aqueous electrolyte has been developed that uses an ex situ oxidation-reduction cycle to precondition a planar silver electrode. Cyanide ion can be detected in 0.1 M KCI with a linear response between 100 ppm and 10 ppb. The estimated limit of detection is approximately 8 ppb. The effects of pH, electrolyte level, and two common background ions, nitrate (NO₃-) and sulfate (SO₄^2-), have been characterized. Cyanide response was found to be sensitive to pH, with optimal performance observed at neutral to basic pH. Electrolyte concentrations of 0.001 M reduced response to cyanide by a factor of five, while levels above 0.1 M had no significant effect. The addition of 10-ppm sulfate ion decreased response approximately 40%, while the presence of nitrate ion at concentrations up to 100 ppm had a negligible effect on SERS response. These results suggest that cyanide ion can be detected directly in high-ionic-strength aqueous solutions, such as groundwater.