Investigation of interfering species in phytodrug analysis using an inhibition tyrosinase enzyme electrode working both in water and in organic solvent

In recent years several inhibition biosensors have been proposed for the analysis of aqueous solutions of phytodrugs. We recently built an inhibition OPEE (organic phase enzyme electrode) based on the inhibition of tyrosinase for the analysis of triazine, carbamate, and organophosphate pesticides operating in water-saturated chloroform. It was possible to determine the concentration of these pesticides contained in lipophilic or aqueous samples by relating it to the inhibiting action measured directly in water, or in water-saturated chloroform, after using the same solvent to extract the pesticides themselves. In the present investigation, attention was focused above all on two points of particular interest: on the study of potential interferents, i.e., of other inhibitors of the tyrosinase enzyme consisting above all, when operating in aqueous solution, of different heavy metal ions or several carboxylic acids, such as cinnamic, sorbic, or benzoic acids, which can apparently interfere in inhibition analysis of pesticides in aqueous matrixes; in the second place, on a detailed comparison of the results of the analysis of triazine, organophosphate, and carbamate pesticides in the presence of the above-mentioned interferents operating both in aqueous solution and in water-saturated chloroform.