Application of Allura Red in the construction of a novel amperometric flow sensor for the automatic determination of hydroquinone and catechol using a two-line flow injection manifold with a single-sensor/double-pulse amperometric detection

Abstract

A novel amperometric flow sensor was constructed by the successive voltammetric cycling of a glassy carbon electrode (GCE) in a basic solution of Allura Red. The performance of the constructed treated GCE sensor was characterized in the new flow injection amperometric manifold with a single-sensor/double-pulse amperometric simultaneous detection of hydroquinone (HQ) and catechol (CC). A programmed sequence of two potential steps with magnitudes of +0.18 (at the time of the first sample injection) and +0.26 V (at the time of the second injection) was applied. By designing a proper time delay between a sequence of two sample injections and potential steps, two separate flow injection amperometric peaks were recorded. The first peak corresponds to HQ and the second peak is related to the oxidation of both HQ and CC. The currents obtained from the subtraction of two recorded peaks is utilized to obtain the amount of CC. Under the optimized chemical and instrumental parameters, the relation between the concentration and response of the sensor has a good linearity in the ranges of 0.2–600.0 and 0.2–300.0 µmol l−1 for HQ and CC, respectively. The detection limit obtained for both was 0.15 µmol l−1 (signal-to-noise ratio = 3). The proposed flow sensor was employed for the determination of HQ and CC in the real samples with satisfying precision and accuracy.