Measurement of fatty amine ethoxylate surfactants using electrochemiluminescence Original Research Article

Direct incorporation of fatty amine ethoxylate surfactants (trade names Ethomeen T/15 and Ethomeen T/25) into an electrochemiluminescence (ECL) reaction sequence is reported. A linear relationship between ECL intensity and concentration of surfactants exists using Ru(bpy)32+ (bpy: 2,2′-bipyridine) as the light emitting molecule. Detection limits of 0.7 ppm (mg/l) and 0.9 ppm have been observed for Ethomeen T/15 in aqueous buffer and seawater, respectively. Detection limits of 1.1 ppm have been achieved for Ethomeen T/25. ECL intensity versus electrochemical potential profiles show that emission occurs at potentials corresponding to the oxidation of both Ethomeen and Ru(bpy)32+. The ECL emission is also pH dependent, with maximum intensities observed at pH ∼8. These results parallel those observed when tri-n-propylamine is substituted for Ethomeen T/15 or T/25 and indicate a possible mechanism for ECL generation.