Hydrocarbon pasting liquids for improved tyrosinase‐based carbon‐paste phenol biosensors

Abstract

Short‐chain hydrocarbons are used as pasting liquids in carbon‐paste tyrosinase amperometric biosensors. The response of the phenolic substrates decreases rapidly upon increasing the chain length of the hydrocarbon binder from C₁₀ to C₁₄, and then it levels off to a size similar to that of the mineral oil biosensor. For example, the dodecane‐based enzyme electrode offers a 17.8‐fold signal enhancement compared to the mineral‐oil one. Such sensitivity enhancements are attributed to the extractive accumulation of the phenolic substrates. The change in the carbon‐paste binder influences also the selectivity of the tyrosinase electrode and the K_{m, app} values. Flow‐injection analysis yields a detection limit of 6 nM catechol and a relative standard deviation of 2.5% (n = 30). A dual enzyme electrode chromatographic detection, based on the use of different pasting liquids, provides unique characterization of the phenolic substrates. The merits of this strategy are illustrated in connection with a river water sample.