Disposable electrochemical sensor for tryptamine detection using a graphite sheet electrode modified with poly(toluidine blue)

Tryptamine (TRYP) is a biogenic amine present in several foods and beverages, and despite some beneficial effects on human health, high intakes of TRYP can be harmful. Therefore, accurate analytical methods for TRYP quantification in food samples are necessary. This study describes a cost-effective electrochemical sensor for TRYP determination in cheese samples based on a poly(toluidine blue) (PTB) film electropolymerized onto graphite sheets (GS). Electrode preparation involved two simple steps: (1) electropolymerization of toluidine blue by potential cycling in phosphate buffer solution, and (2) PTB overoxidation by potential cycling in a 0.1 mol L-1 KOH solution. The overoxidation of PTB led to a remarkable increase in sensitivity and detectability towards TRYP, due to the introduction of negatively charged groups that electrostatically preconcentrate TRYP at electrode surface. Using square wave voltammetry, a linear range for TRYP from 0.05 to 0.9 & mu;mol L-1 (0.008 - 0.144 ppm) was achieved with a detection limit of 12 nmol L-1 (0.002 ppm). Also, the electrodes exhibited a remarkable antifouling ability leading to highly reproducible voltammetric responses for TRYP. In addition to being inexpensive (disposable), GS substrates enabled PTB electropolymerization with no need for cleaning or surface preparation procedures. Therefore, the approach described here proved to be promising for the simple, inexpensive, and accurate determination of TRYP in cheese samples.