Waveform optimization for integrated square-wave detection of biogenic amines following their liquid chromatographic separation

Results are described from research designed to optimize the potential–time (E–t) waveform applied in integrated square-wave detection (ISWD). More specifically, goals of this study included the minimization of background signal with maximization of the signal-to-background ratio (S/B) for application of ISWD to polyamines separated by high performance cation-exchange liquid chromatography (LC). This effort included optimization of the separation procedure because the background signal was determined to be a sensitive function of the composition of the chromatographic mobile phase. Initial estimates of potential parameters were obtained from an off-line voltammetric study of 1,3-diaminopropane at a gold rotated disk electrode (RDE). Final waveform optimization was based on data obtained during on-line application of the ISWD waveform for 1,3-diaminopropane injected at various times during execution of the mobile phase gradient. The maximum potential in the waveform (E_MAX) was chosen to achieve formation of surface oxide (AuO) with concomitant oxidation of the amine without evolution of O₂. The minimum potential in the waveform (E_MIN) was chosen to achieve reduction of the surface oxide generated at E_MAX with minimal reduction of dissolved O₂.