PARENT SESSION
PT5 - Fate & Effects of Metals: Aquatic Biology
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P634) Measurements of bioavailable copper in aqueous solutions using surface enhanced raman scattering.

Strickland, Aaron^*,1, Corcoran, Robert¹, ¹ University of Wyoming, Laramie, WY, USA

ABSTRACT- It has been clearly demonstrated that the total aqueous concentration of copper is not a good measure of its bioavailability. Much evidence exists that suggests that the free cupric ion (Cu2+) and some labile complexes of the metal better predict the bioavailable fraction of the metal. Although many analytical methods exist for determining aqueous metal concentrations, most either indirectly measure free metal ion concentrations, are very labor intensive, are slow, or give unreliable data. We have developed an analytical method based on surface enhanced Raman scattering (SERS) capable of detecting Cu2+ at nanomolar concentrations in aqueous solutions. A key element of the analytical method is a sensor molecule incorporating a Raman active ligand and a surface-tethering group. Aqueous solutions of our sensor were combined with silver nanoparticles (the surface) and varying concentrations of CuSO4 (10-4M to 10-9M), then analyzed using a Raman spectrometer. These studies were done in the presence of other toxicologically relevant metals (e.g. Ni, Zn, Cd, and Pb), at varying pH (5-7), and in the presence of humic acid. The SERS results show that we can measure Cu2+ at concentrations ranging from parts-per-thousand (ppt) to less than parts-per-billion (ppb) with a detection limit of 0.3 ppb. Furthermore, Cu2+ can be detected in the presence of Ni2+, Zn2+, Cd2+, and Pb2+ as well as in the presence of varying concentrations of humic acid (e.g., ≤ 100 mg/L).

Key words: copper, bioavailable, detection, SERS