Integrated square-wave electrochemical detection of biogenic amines in soybean seeds following their separations by liquid chromatography

A strategy for electrochemical detection (ED), based on digital integration of the current response at a Au electrode resulting from a square potential-time waveform, is applied for the direct detection of organic polyamines in complex samples following their separations using cation-exchange liquid chromatography (CELC). The samples consist of soybean extracts and are injected in acidic media to facilitate adsorption on the cation-exchange chromatographic phase. Alkaline buffer is mixed with the chromatographic effluent to facilitate ED. Whereas emphasis is given to the CELC-ED methodology, comparison is made with the more traditional application of photometric detection (PD) of the derivatized amines following their separation by reversed phase liquid chromatography (RPLC). Estimated detection limits are significantly lower for CELC-ED in comparison with RPLC-PD. For example, detection limits (25µl injections) for 1,4-diaminopropane (putrescine) are 200 and 8000pmoles for CELC-ED and RPLC-PD, respectively. Detection limits for 1,5-diaminopentane (cadavarine) are 190 and 9000pmoles for CELC-ED and RPLC-PD, respectively. Furthermore, baseline drift under the associated gradient elution programs, is significantly less for CELC-ED in comparison to RPLC-PD.