SURFACE-ENHANCED RESONANCE RAMAN-SPECTROSCOPY OF IRON DOPAMINE COMPLEXES

Surface-enhanced resonance Raman spectroscopy (SERRS) at silver colloi ds is used to detect the catecholamines, 3-hydroxytyramine (dopamine) and 3,4-dihydroxyphenylacetic acid (DOPAC), in a modified Ringer's sol ution. Catecholamines form very strong complexes with iron(III) in sol ution (K(f) > 10(40)) and exhibit a broad ligand-to-metal charge-trans fer (LMCT) absorption in the visible (approximately 500 nm). Resonance enhancement is achieved by excitation at 532 nm from a frequency doub led Nd:YAG laser with high quality spectra attainable in 1 s. Maximum SERRS signal is observed when basic buffer is added to a dopamine samp le containing 50 x 10(-6) M ferric ion. Dopamine concentrations in the nanomolar (resting level) range are obtained using this technique.