Stabilization of the voltammetric serotonin signal by surfactants

Abstract Electrode fouling by oxidation products of the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) resulted in a fall-off of its voltammetric signal by 66% during 21 repeated scans, but the fall-off was reduced to, respectively, 7% and 10% in the presence of 5000 mg L −1 of the cationic surfactants cetyl trimethyl ammonium chloride (CTAC) and cetyl pyridinium chloride (CPC). Addition of only 1 mg L −1 of CTAC or CPC also had a significant, albeit smaller, stabilizing effect. The anionic surfactants sodium dodecyl sulfate and sodium decyl sulfonate also stabilized the 5-HT signal, but less so than the cationic surfactants while nonionic surfactants were least effective. The peak height of 5-HT was reduced by between 40% and 50% by CTAC and CPC while the anionic surfactants only had a marked effect on the peak height at the highest surfactant concentrations tested (1000 and 5000 mg L −1 ). Adsorbed oxidation products of 5-HT on the electrode surface are not removed by the surfactants, and they must therefore be added to the sample prior to the measurements. The experimental results are interpreted in terms of the surface activity and aggregation behavior of the surfactants.