Voltammetric Detection of Dihydroxybenzene Isomers By Modified Graphite Paste Electrode with Prussian Blue-Nanosized Polyaniline Hybrid
Authors: Patel Bhargav R , Noroozifar Meissam , Kerman Kagan 
Published: May 2020

The dihydroxybenzene isomers (DHB); catechol (1, 2-dihydroxybenzene, CC), resorcinol (1, 3-dihydroxybenzene, RC) and hydroquinone (1,4-dihydroxybenzene, HQ) are well-known organic pollutants and are widely distributed in the environment. DHB isomers are frequently used as starting materials and industrial reagents in various industries for production of plastic, tanning, pharmaceuticals, paint, paper, cosmetics and rubber.1–4 Furthermore, these isomers are also found as important side products from the industrial effluents of photo-processing companies, oil refineries, coal-tar, steel, paper and pulp mills in concentrations ranging between 1 to 1000 ppm.4,5 Due to their toxicity and the health risks associated with their use, national environmental agencies from United States and European Union have categorized them as primary wastewater pollutants.6 In addition, Health Canada has also listed them under the List of Prohibited and Restricted Cosmetic Ingredients (Cosmetic Ingredient Hotlist).7

As an electroactive polymer, polyaniline (PANI) is known to have good environmental stability, conductivity and redox properties. It has also been recently used in electrochemical biosensors due to the ease of synthesis, cheap cost and simple doping mechanisms. Prussian blue (PB) is another redox substance which also possesses good conductivity and unique electrocatalytic characteristics. In this study, modified graphite paste electrode (GPE) with PB doped nanosized-PANI hybrid (PB@n-PANI/GPE) was used for simultaneous detection of DHB isomers using differential pulse voltammetry (DPV). Prussian blue doped nanosized-polyaniline (PB@n-PANI) was synthesized in two-steps, firstly, aniline and ferric (III) chloride salt reacted through in situ mechano-chemical reactions to produce nanosized-PANI polymer. Secondly, potassium hexacyanoferrate (II) solution was added to the product of step one and the polymer was doped by PB in a solid-state and template-free technique to generate PB@n-PANI. The synthesized hybrid was then characterized by different microscopic and spectroscopic techniques. The PB@n-PANI modified GPE exhibited three well-separated oxidation peaks at potentials 0.24, 0.36 and 0.74 V for HQ, CC and RC, respectively (Fig. 1). The analytical performance of the PB@n-PANI/GPE has been studied for simultaneous determination of HQ, CC and RS in different real sample matrices with satisfactory recoveries. Furthermore, different electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry have been used to perform electrochemical surface characterization of the modified GPE. The results from CV and ESI were used to evaluate the charge transfer properties of the PB@n-PANI/GPE and the results from chronoamperometric studies were used to calculate the diffusion coefficients of the DHB isomers. In addition, active surface area of the modified GPE and the standard heterogenous rate constant for the DHB isomers have also been calculated. Overall, we have demonstrated that the presence of PB and n-PANI enhances the redox-active surface area and plays a synergistic role in improving the electrocatalytic activity of the PB@n-PANI/GPE. Therefore, PB@n-PANI/GPE is a promising analytical platform for simultaneous detection of DHB isomers.

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Figure 1