A Novel Sensor Based on Manganese azo-Macrocycle/Carbon Nanotubes to Perform the Oxidation and Reduction Processes of Two Diphenol Isomers

The present work describes the development of a selective and sensitive voltammetric sensor for simulta- neous determination of catechol (CC) and hydroquinone (HQ), based on a glassy carbon (GC) electrode modified with manganese phthalocyanine azo-macrocycle (MnPc) adsorbed on multiwalled carbon nanotubes (MWCNT). Scanning electron microscopy and scanning electrochemi- cal microscopy were used to characterize the composite material (MnPc/MWCNT) on the glassy carbon electrode surface. The modified electrode showed excellent electro- chemical activity towards the simultaneous oxidation and reduction of CC and HQ. On the MnPc/MWCNT/GC electrode, both CC and HQ can generate a pair of quasi- reversible and well-defined redox peaks. Under optimized experimental and operational conditions, the cathodic peak currents were linear over the range 1-600 mmol L � 1 for both CC and HQ, with limits of detection of 0.095 and 0.041 mmol L � 1 , respectively. The anodic peak cur- rents were also linear over the range 1-600 mmol L � 1 for both CC and HQ, with limits of detection of 0.096 and 0.048 mmol L � 1 , respectively. The proposed method was effectively applied for the simultaneous detection of hy- droquinone and catechol in water samples and the results were in agreement with those obtained by a comparative method described in the literature.